Question:
What do these two changes have in common?
sediment settling to the bottom of a muddy puddle
dry ice sublimating and becoming a gas

Choices:
A. Both are caused by heating.
B. Both are caused by cooling.
C. Both are chemical changes.
D. Both are only physical changes.

Matter is made of very small particles called atoms. Atoms can be linked together by chemical bonds. When two or more atoms link together, they form a molecule.
In a chemical change, the chemical bonds in the molecules break. The atoms then link together to form different molecules. The types of molecules in matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. As paper burns, paper molecules react with oxygen molecules in the air. This reaction breaks the chemical bonds in the molecules. The atoms then link together in a different way to form different molecules. For example, carbon dioxide molecules are formed when paper burns.
In a physical change, chemical bonds do not break. The types of molecules in matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, water vaporizing is a physical change that can be caused by heating. Liquid water and water vapor are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
Loose matter such as sand and dirt is called sediment. Sediment settling to the bottom of a muddy puddle is a physical change.
The sediment sinks, and the water above becomes clearer. This separates the water from the sediment. But separating a mixture does not form a different type of matter.
Dry ice is solid carbon dioxide. When dry ice gets warm, it changes state and becomes carbon dioxide gas. This change of state, from solid to gas, is called sublimation.
Dry ice becoming a gas is a physical change. A change of state does not form a different type of matter.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are physical changes. No new matter is created.
Both are chemical changes.
Both changes are physical changes. They are not chemical changes.
Both are caused by heating.
Dry ice sublimating is caused by heating. But sediment settling to the bottom of a muddy puddle is not.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: Select the living thing.

Choices:
A. pushpin
B. fig tree
C. shoe
D. iceberg

All living things are made up of cells. Plants, animals, and some fungi have many cells. Other living things are made up of just one cell.
All living things need food and water. Water helps living things break down food and remove waste. Food gives living things energy. They use energy from food to grow and change.
All living things sense changes in their environment. Living things might sense changes by seeing, smelling, hearing, or feeling. Living things can respond to the changes they sense.

A fig tree is a living thing.
Fig trees grow and respond to their environment. They need food and water. Fig trees are made up of many cells.
Fig trees are plants. They make their own food using water, carbon dioxide, and energy from sunlight.
An iceberg is not a living thing.
An iceberg does not have all the traits of a living thing. It may grow or melt in response to the world around it, but it does not need food.
A pushpin is not a living thing.
Pushpins do not have all of the traits of living things. They do not grow or respond to their environment. They do not need food or water.
A shoe is not a living thing.
Shoes do not have all of the traits of living things. They do not grow or respond to their environment. They do not need food or water.

natural science

local parquet snapshot does not include README/license metadata; verify upstream before public upload


Question:
What do these two changes have in common?
baking an apple pie
using polish to remove tarnish from a silver spoon

Choices:
A. Both are caused by heating.
B. Both are chemical changes.
C. Both are only physical changes.
D. Both are caused by cooling.

Chemical changes and physical changes are two common ways matter can change.
In a chemical change, the type of matter changes. The types of matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. When paper gets hot enough, it reacts with oxygen in the air and burns. The paper and oxygen change into ash and smoke.
In a physical change, the type of matter stays the same. The types of matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, ice melting is a physical change that can be caused by heating. Ice and liquid water are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
Baking an apple pie is a chemical change. The type of matter in the pie changes when it is baked. The crust turns brown, and the apples become soft.
A tarnished silver spoon is one that has become less shiny over time. Polishing the spoon makes it look shiny again.
The polish changes the tarnish into a different type of matter that can be easily wiped away. So, using polish to remove tarnish from silver is a chemical change.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are chemical changes. They are not physical changes.
Both are chemical changes.
Both changes are chemical changes. The type of matter before and after each change is different.
Both are caused by heating.
Baking is caused by heating. But polish removing tarnish from a silver spoon is not.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question:
What do these two changes have in common?
sediment settling to the bottom of a muddy puddle
an iceberg melting slowly

Choices:
A. Both are caused by cooling.
B. Both are only physical changes.
C. Both are chemical changes.
D. Both are caused by heating.

Matter is made of very small particles called atoms. Atoms can be linked together by chemical bonds. When two or more atoms link together, they form a molecule.
In a chemical change, the chemical bonds in the molecules break. The atoms then link together to form different molecules. The types of molecules in matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. As paper burns, paper molecules react with oxygen molecules in the air. This reaction breaks the chemical bonds in the molecules. The atoms then link together in a different way to form different molecules. For example, carbon dioxide molecules are formed when paper burns.
In a physical change, chemical bonds do not break. The types of molecules in matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, water vaporizing is a physical change that can be caused by heating. Liquid water and water vapor are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
Loose matter such as sand and dirt is called sediment. Sediment settling to the bottom of a muddy puddle is a physical change.
The sediment sinks, and the water above becomes clearer. This separates the water from the sediment. But separating a mixture does not form a different type of matter.
An iceberg melting is a change of state. So, it is a physical change. An iceberg is made of frozen water. As it melts, the water changes from a solid to a liquid. But a different type of matter is not formed.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are physical changes. No new matter is created.
Both are chemical changes.
Both changes are physical changes. They are not chemical changes.
Both are caused by heating.
An iceberg melting is caused by heating. But sediment settling to the bottom of a muddy puddle is not.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: Select the bird below.

Choices:
A. Galapagos giant tortoise
B. western gorilla
C. albatross
D. rabbit

Birds have feathers, two wings, and a beak.
Birds are warm-blooded. Warm-blooded animals can control their body temperature.
A griffon vulture is an example of a bird.

Birds, mammals, fish, reptiles, and amphibians are groups of animals. Scientists sort animals into each group based on traits they have in common. This process is called classification.
Classification helps scientists learn about how animals live. Classification also helps scientists compare similar animals.

A rabbit is a mammal. It has fur and feeds its young milk.
Rabbits live underground in burrows. A group of rabbit burrows is called a warren.
An albatross is a bird. It has feathers, two wings, and a beak.
Albatrosses live near the ocean. They hunt squid, fish, and other small animals.
A Galapagos giant tortoise is a reptile. It has scaly, waterproof skin.
Galapagos tortoises live on the Galapagos Islands in the Pacific Ocean. They can live to be over 150 years old!
A western gorilla is a mammal. It has fur and feeds its young milk.
Gorillas live in groups called troops. The largest male in the troop is usually the leader.

natural science

Identify mammals, birds, fish, reptiles, and amphibians


Question: How long is a soccer field?

Choices:
A. 370 miles
B. 370 yards
C. 370 feet
D. 370 inches

Select the best estimate.

Measurements are written with both a number and a unit. The unit comes after the number. The unit shows what the number means.
When you are using customary units, length may be written with units of inches, feet, yards, or miles.
There are 12 inches in 1 foot, and 3 feet in 1 yard. There are 5,280 feet in 1 mile.
A football is about 1 foot long. A football field is 100 yards long.

The best estimate for the length of a soccer field is 370 feet.
370 inches is too short. 370 yards and 370 miles are too long.

natural science

Choose customary units of distance, mass, and volume


Question:
What do these two changes have in common?
a puddle freezing into ice on a cold night
mixing sand and water

Choices:
A. Both are chemical changes.
B. Both are only physical changes.
C. Both are caused by heating.
D. Both are caused by cooling.

Matter is made of very small particles called atoms. Atoms can be linked together by chemical bonds. When two or more atoms link together, they form a molecule.
In a chemical change, the chemical bonds in the molecules break. The atoms then link together to form different molecules. The types of molecules in matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. As paper burns, paper molecules react with oxygen molecules in the air. This reaction breaks the chemical bonds in the molecules. The atoms then link together in a different way to form different molecules. For example, carbon dioxide molecules are formed when paper burns.
In a physical change, chemical bonds do not break. The types of molecules in matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, water vaporizing is a physical change that can be caused by heating. Liquid water and water vapor are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
A puddle freezing into ice on a cold night is a change of state. So, it is a physical change. Liquid water freezes and becomes solid, but it is still made of water. A different type of matter is not formed.
Mixing sand and water is a physical change. Adding water makes the sand wet. But both the sand and water are still made of the same type of matter as before.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are physical changes. No new matter is created.
Both are chemical changes.
Both changes are physical changes. They are not chemical changes.
Both are caused by heating.
Neither change is caused by heating.
Both are caused by cooling.
A puddle freezing is caused by cooling. But mixing sand and water is not.

natural science


Question: Which of these organisms contains matter that was once part of the lichen?

Choices:
A. rough-legged hawk
B. barren-ground caribou
C. parasitic jaeger
D. Arctic fox
E. snowy owl

Below is a food web from a tundra ecosystem in Nunavut, a territory in Northern Canada.
A food web models how the matter eaten by organisms moves through an ecosystem. The arrows in a food web represent how matter moves between organisms in an ecosystem.

A food web is a model.
A food web shows where organisms in an ecosystem get their food. Models can make things in nature easier to understand because models can represent complex things in a simpler way. If a food web showed every organism in an ecosystem, the food web would be hard to understand. So, each food web shows how some organisms in an ecosystem can get their food.
Arrows show how matter moves.
A food web has arrows that point from one organism to another. Each arrow shows the direction that matter moves when one organism eats another organism. An arrow starts from the organism that is eaten. The arrow points to the organism that is doing the eating.
An organism in a food web can have more than one arrow pointing from it. This shows that the organism is eaten by more than one other organism in the food web.
An organism in a food web can also have more than one arrow pointing to it. This shows that the organism eats more than one other organism in the food web.

Use the arrows to follow how matter moves through this food web. For each answer choice, try to find a path of arrows that starts from the lichen.
The only arrow pointing to the rough-legged hawk starts from the parasitic jaeger. The only arrow pointing to the parasitic jaeger starts from the brown lemming. The brown lemming has two arrows pointing to it. These arrows start from the bear sedge and the bilberry. Neither the bear sedge nor the bilberry has any arrows pointing to it. So, in this food web, matter does not move from the lichen to the rough-legged hawk.
The only arrow pointing to the snowy owl starts from the short-tailed weasel. The only arrow pointing to the short-tailed weasel starts from the brown lemming. The brown lemming has two arrows pointing to it. These arrows start from the bear sedge and the bilberry. Neither the bear sedge nor the bilberry has any arrows pointing to it. So, in this food web, matter does not move from the lichen to the snowy owl.
The only arrow pointing to the parasitic jaeger starts from the brown lemming. The brown lemming has two arrows pointing to it. These arrows start from the bear sedge and the bilberry. Neither the bear sedge nor the bilberry has any arrows pointing to it. So, in this food web, matter does not move from the lichen to the parasitic jaeger.There is one path matter can take from the lichen to the barren-ground caribou: lichen->barren-ground caribou. Arctic fox. The Arctic fox has two arrows pointing to it. One arrow starts from the bilberry. The bilberry does not have any arrows pointing to it. The other arrow pointing to the Arctic fox starts from the brown lemming. The brown lemming has two arrows pointing to it. These arrows start from the bear sedge and the bilberry. Neither the bear sedge nor the bilberry has any arrows pointing to it. So, in this food web, matter does not move from the lichen to the Arctic fox..

natural science


Question: How long is a raisin?

Choices:
A. 11 centimeters
B. 11 kilometers
C. 11 meters
D. 11 millimeters

Select the best estimate.

Measurements are written with both a number and a unit. The unit comes after the number. The unit shows what the number means.
When you are using metric units, length can be written with units of millimeters, centimeters, meters, or kilometers. One meter contains 100 centimeters or 1,000 millimeters. So, 1 meter is larger than 1 centimeter, and 1 centimeter is larger than 1 millimeter.
The tip of the pencil shown here is only 1 millimeter wide, but the pencil is about 16 centimeters long.
A red fox is about 1 meter long. The Sydney Harbour Bridge in Australia is about 1,000 meters, or 1 kilometer, in length.

The best estimate for the length of a raisin is 11 millimeters.
11 centimeters, 11 meters, and 11 kilometers are all too long.

natural science

Choose metric units of distance, mass, and volume


Question:
What do these two changes have in common?
mixing sand and water
carving a piece of wood

Choices:
A. Both are only physical changes.
B. Both are caused by cooling.
C. Both are caused by heating.
D. Both are chemical changes.

Chemical changes and physical changes are two common ways matter can change.
In a chemical change, the type of matter changes. The types of matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. When paper gets hot enough, it reacts with oxygen in the air and burns. The paper and oxygen change into ash and smoke.
In a physical change, the type of matter stays the same. The types of matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, ice melting is a physical change that can be caused by heating. Ice and liquid water are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
Mixing sand and water is a physical change. Adding water makes the sand wet. But both the sand and water are still made of the same type of matter as before.
Carving a piece of wood is a physical change. The wood changes shape, but it is still made of the same type of matter.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are physical changes. No new matter is created.
Both are chemical changes.
Both changes are physical changes. They are not chemical changes.
Both are caused by heating.
Neither change is caused by heating.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: Select the solid.

Choices:
A. water from a faucet
B. screwdriver
C. grape juice
D. air from a hair dryer

Solid, liquid, and gas are states of matter. Matter is anything that takes up space. Matter can come in different states, or forms.
When matter is a solid, it has a definite volume and a definite shape. So, a solid has a size and shape of its own.
Some solids can be easily folded, bent, or broken. A piece of paper is a solid. Also, some solids are very small. A grain of sand is a solid.
When matter is a liquid, it has a definite volume but not a definite shape. So, a liquid has a size of its own, but it does not have a shape of its own. Think about pouring juice from a bottle into a cup. The juice still takes up the same amount of space, but it takes the shape of the bottle.
Some liquids do not pour as easily as others. Honey and milk are both liquids. But pouring honey takes more time than pouring milk.
When matter is a gas, it does not have a definite volume or a definite shape. A gas expands, or gets bigger, until it completely fills a space. A gas can also get smaller if it is squeezed into a smaller space.
Many gases are invisible. Air is a gas.

The air from a hair dryer is a gas. A gas expands to fill a space. A hair dryer uses a fan to blow warm air out. When the air leaves the hair dryer, the air expands to fill a much large space.
The water from a faucet is a liquid. A liquid takes the shape of any container it is in. If you put water from a faucet into a container, the water will take the shape of that container. But the water will still take up the same amount of space.
A screwdriver is a solid. A solid has a size and shape of its own. This screwdriver has a metal blade and a plastic handle. Both metal and plastic are solids.
Grape juice is a liquid. A liquid takes the shape of any container it is in. If you pour grape juice into a different container, the grape juice will take the shape of that container. But the grape juice will still take up the same amount of space.

natural science


Question: What is the expected ratio of offspring that have horns to offspring that do not have horns? Choose the most likely ratio.

Choices:
A. 2:2
B. 3:1
C. 1:3
D. 4:0
E. 0:4

In a group of cows, some individuals have horns and others do not. In this group, the gene for the horns trait has two alleles. The allele for having horns (h) is recessive to the allele for not having horns (H).
This Punnett square shows a cross between two cows.

Offspring phenotypes: dominant or recessive?
How do you determine an organism's phenotype for a trait? Look at the combination of alleles in the organism's genotype for the gene that affects that trait. Some alleles have types called dominant and recessive. These two types can cause different versions of the trait to appear as the organism's phenotype.
If an organism's genotype has at least one dominant allele for a gene, the organism's phenotype will be the dominant allele's version of the gene's trait.
If an organism's genotype has only recessive alleles for a gene, the organism's phenotype will be the recessive allele's version of the gene's trait.
A Punnett square shows what types of offspring a cross can produce. The expected ratio of offspring types compares how often the cross produces each type of offspring, on average. To write this ratio, count the number of boxes in the Punnett square representing each type.
For example, consider the Punnett square below.
 | F | f
F | FF | Ff
f | Ff | ff
There is 1 box with the genotype FF and 2 boxes with the genotype Ff. So, the expected ratio of offspring with the genotype FF to those with Ff is 1:2.

To determine how many boxes in the Punnett square represent offspring that do or do not have horns, consider whether each phenotype is the dominant or recessive allele's version of the horns trait. The question tells you that the h allele, which is for having horns, is recessive to the H allele, which is for not having horns.
Having horns is the recessive allele's version of the horns trait. A cow with the recessive version of the horns trait must have only recessive alleles for the horns gene. So, offspring that have horns must have the genotype hh.
There are 0 boxes in the Punnett square with the genotype hh.
Not having horns is the dominant allele's version of the horns trait. A cow with the dominant version of the horns trait must have at least one dominant allele for the horns gene. So, offspring that do not have horns must have the genotype HH or Hh.
All 4 boxes in the Punnett square have the genotype HH or Hh.
So, the expected ratio of offspring that have horns to offspring that do not have horns is 0:4. This means that, based on the Punnett square, this cross will never produce offspring that have horns. Instead, this cross is expected to always produce offspring that do not have horns.

natural science

Use Punnett squares to calculate ratios of offspring types


Question: How long is a sunflower seed?

Choices:
A. 12 millimeters
B. 12 kilometers
C. 12 meters
D. 12 centimeters

Select the best estimate.

Measurements are written with both a number and a unit. The unit comes after the number. The unit shows what the number means.
When you are using metric units, length can be written with units of millimeters, centimeters, meters, or kilometers. One meter contains 100 centimeters or 1,000 millimeters. So, 1 meter is larger than 1 centimeter, and 1 centimeter is larger than 1 millimeter.
The tip of the pencil shown here is only 1 millimeter wide, but the pencil is about 16 centimeters long.
A red fox is about 1 meter long. The Sydney Harbour Bridge in Australia is about 1,000 meters, or 1 kilometer, in length.

The best estimate for the length of a sunflower seed is 12 millimeters.
12 centimeters, 12 meters, and 12 kilometers are all too long.

natural science


Question: What is the expected ratio of offspring with a reddish-brown coat to offspring with a black coat? Choose the most likely ratio.

Choices:
A. 2:2
B. 4:0
C. 3:1
D. 1:3
E. 0:4

In a group of horses, some individuals have a black coat and others have a reddish-brown coat. In this group, the gene for the coat color trait has two alleles. The allele for a black coat (L) is dominant over the allele for a reddish-brown coat (l).
This Punnett square shows a cross between two horses.

Offspring phenotypes: dominant or recessive?
How do you determine an organism's phenotype for a trait? Look at the combination of alleles in the organism's genotype for the gene that affects that trait. Some alleles have types called dominant and recessive. These two types can cause different versions of the trait to appear as the organism's phenotype.
If an organism's genotype has at least one dominant allele for a gene, the organism's phenotype will be the dominant allele's version of the gene's trait.
If an organism's genotype has only recessive alleles for a gene, the organism's phenotype will be the recessive allele's version of the gene's trait.
A Punnett square shows what types of offspring a cross can produce. The expected ratio of offspring types compares how often the cross produces each type of offspring, on average. To write this ratio, count the number of boxes in the Punnett square representing each type.
For example, consider the Punnett square below.
 | F | f
F | FF | Ff
f | Ff | ff
There is 1 box with the genotype FF and 2 boxes with the genotype Ff. So, the expected ratio of offspring with the genotype FF to those with Ff is 1:2.

To determine how many boxes in the Punnett square represent offspring with a reddish-brown coat or a black coat, consider whether each phenotype is the dominant or recessive allele's version of the coat color trait. The question tells you that the L allele, which is for a black coat, is dominant over the l allele, which is for a reddish-brown coat.
A reddish-brown coat is the recessive allele's version of the coat color trait. A horse with the recessive version of the coat color trait must have only recessive alleles for the coat color gene. So, offspring with a reddish-brown coat must have the genotype ll.
There are 2 boxes in the Punnett square with the genotype ll. These boxes are highlighted below.
A black coat is the dominant allele's version of the coat color trait. A horse with the dominant version of the coat color trait must have at least one dominant allele for the coat color gene. So, offspring with a black coat must have the genotype LL or Ll.
There are 2 boxes in the Punnett square with the genotype LL or Ll. These boxes are highlighted below.
So, the expected ratio of offspring with a reddish-brown coat to offspring with a black coat is 2:2. This means that, on average, this cross will produce 2 offspring with a reddish-brown coat for every 2 offspring with a black coat.

natural science


Question: How long is a caterpillar?

Choices:
A. 21 millimeters
B. 21 centimeters
C. 21 meters
D. 21 kilometers

Select the best estimate.

Measurements are written with both a number and a unit. The unit comes after the number. The unit shows what the number means.
When you are using metric units, length can be written with units of millimeters, centimeters, meters, or kilometers. One meter contains 100 centimeters or 1,000 millimeters. So, 1 meter is larger than 1 centimeter, and 1 centimeter is larger than 1 millimeter.
The tip of the pencil shown here is only 1 millimeter wide, but the pencil is about 16 centimeters long.
A red fox is about 1 meter long. The Sydney Harbour Bridge in Australia is about 1,000 meters, or 1 kilometer, in length.

The best estimate for the length of a caterpillar is 21 millimeters.
21 centimeters, 21 meters, and 21 kilometers are all too long.

natural science


Question:
What do these two changes have in common?
baking a loaf of bread
melting glass

Choices:
A. Both are chemical changes.
B. Both are caused by cooling.
C. Both are only physical changes.
D. Both are caused by heating.

Chemical changes and physical changes are two common ways matter can change.
In a chemical change, the type of matter changes. The types of matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. When paper gets hot enough, it reacts with oxygen in the air and burns. The paper and oxygen change into ash and smoke.
In a physical change, the type of matter stays the same. The types of matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, ice melting is a physical change that can be caused by heating. Ice and liquid water are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
Baking a loaf of bread is a chemical change. The type of matter in the dough changes when it is baked. The dough turns into bread!
Melting glass is a change of state. So, it is a physical change. The glass changes from solid to liquid. But a different type of matter is not formed.
Step 2: Look at each answer choice.
Both are only physical changes.
Melting glass is a physical change. But baking bread is not.
Both are chemical changes.
Baking bread is a chemical change. But melting glass is not.
Both are caused by heating.
Both changes are caused by heating.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: How long is an eyelash?

Choices:
A. 8 centimeters
B. 8 meters
C. 8 kilometers
D. 8 millimeters

Select the best estimate.

Measurements are written with both a number and a unit. The unit comes after the number. The unit shows what the number means.
When you are using metric units, length can be written with units of millimeters, centimeters, meters, or kilometers. One meter contains 100 centimeters or 1,000 millimeters. So, 1 meter is larger than 1 centimeter, and 1 centimeter is larger than 1 millimeter.
The tip of the pencil shown here is only 1 millimeter wide, but the pencil is about 16 centimeters long.
A red fox is about 1 meter long. The Sydney Harbour Bridge in Australia is about 1,000 meters, or 1 kilometer, in length.

The best estimate for the length of an eyelash is 8 millimeters.
8 centimeters, 8 meters, and 8 kilometers are all too long.

natural science


Question: What is the expected ratio of offspring with sweet fruit to offspring with sour fruit? Choose the most likely ratio.

Choices:
A. 2:2
B. 0:4
C. 4:0
D. 1:3
E. 3:1

In a group of muskmelon plants, some individuals have sour fruit and others have sweet fruit. In this group, the gene for the fruit taste trait has two alleles. The allele for sour fruit (F) is dominant over the allele for sweet fruit (f).
This Punnett square shows a cross between two muskmelon plants.

Offspring phenotypes: dominant or recessive?
How do you determine an organism's phenotype for a trait? Look at the combination of alleles in the organism's genotype for the gene that affects that trait. Some alleles have types called dominant and recessive. These two types can cause different versions of the trait to appear as the organism's phenotype.
If an organism's genotype has at least one dominant allele for a gene, the organism's phenotype will be the dominant allele's version of the gene's trait.
If an organism's genotype has only recessive alleles for a gene, the organism's phenotype will be the recessive allele's version of the gene's trait.
A Punnett square shows what types of offspring a cross can produce. The expected ratio of offspring types compares how often the cross produces each type of offspring, on average. To write this ratio, count the number of boxes in the Punnett square representing each type.
For example, consider the Punnett square below.
 | F | f
F | FF | Ff
f | Ff | ff
There is 1 box with the genotype FF and 2 boxes with the genotype Ff. So, the expected ratio of offspring with the genotype FF to those with Ff is 1:2.

To determine how many boxes in the Punnett square represent offspring with sweet fruit or sour fruit, consider whether each phenotype is the dominant or recessive allele's version of the fruit taste trait. The question tells you that the F allele, which is for sour fruit, is dominant over the f allele, which is for sweet fruit.
Sweet fruit is the recessive allele's version of the fruit taste trait. A muskmelon plant with the recessive version of the fruit taste trait must have only recessive alleles for the fruit taste gene. So, offspring with sweet fruit must have the genotype ff.
There are 2 boxes in the Punnett square with the genotype ff. These boxes are highlighted below.
Sour fruit is the dominant allele's version of the fruit taste trait. A muskmelon plant with the dominant version of the fruit taste trait must have at least one dominant allele for the fruit taste gene. So, offspring with sour fruit must have the genotype FF or Ff.
There are 2 boxes in the Punnett square with the genotype FF or Ff. These boxes are highlighted below.
So, the expected ratio of offspring with sweet fruit to offspring with sour fruit is 2:2. This means that, on average, this cross will produce 2 offspring with sweet fruit for every 2 offspring with sour fruit.

natural science


Question: Select the living thing.

Choices:
A. computer
B. airplane
C. raspberry bush
D. flower pot

All living things are made up of cells. Plants, animals, and some fungi have many cells. Other living things are made up of just one cell.
All living things need food and water. Water helps living things break down food and remove waste. Food gives living things energy. They use energy from food to grow and change.
All living things sense changes in their environment. Living things might sense changes by seeing, smelling, hearing, or feeling. Living things can respond to the changes they sense.

An airplane is not a living thing.
An airplane does not have all the traits of a living thing. It needs energy to fly, but it does not eat food. Airplanes get energy from gasoline or other fuel. They do not grow.
A raspberry bush is a living thing.
Raspberry bushes grow and respond to their environment. They need food and water. Raspberry bushes are made up of many cells.
Raspberry bushes are plants. They make their own food using water, carbon dioxide, and energy from sunlight.
A computer is not a living thing.
A computer does not have all the traits of a living thing. It does many useful things, and even responds to the world around it. But it does not grow. It does not need food or water.
A flower pot is not a living thing.
Flower pots do not have all of the traits of living things. They do not grow or respond to their environment. They do not need food or water.

natural science


Question: How long is a human front tooth?

Choices:
A. 11 meters
B. 11 centimeters
C. 11 kilometers
D. 11 millimeters

Select the best estimate.

Measurements are written with both a number and a unit. The unit comes after the number. The unit shows what the number means.
When you are using metric units, length can be written with units of millimeters, centimeters, meters, or kilometers. One meter contains 100 centimeters or 1,000 millimeters. So, 1 meter is larger than 1 centimeter, and 1 centimeter is larger than 1 millimeter.
The tip of the pencil shown here is only 1 millimeter wide, but the pencil is about 16 centimeters long.
A red fox is about 1 meter long. The Sydney Harbour Bridge in Australia is about 1,000 meters, or 1 kilometer, in length.

The best estimate for the length of a human front tooth is 11 millimeters.
11 centimeters, 11 meters, and 11 kilometers are all too long.

natural science


Question:
What do these two changes have in common?
snails growing shells
photosynthesis

Choices:
A. Both are chemical changes.
B. Both are caused by heating.
C. Both are caused by cooling.
D. Both are only physical changes.

Matter is made of very small particles called atoms. Atoms can be linked together by chemical bonds. When two or more atoms link together, they form a molecule.
In a chemical change, the chemical bonds in the molecules break. The atoms then link together to form different molecules. The types of molecules in matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. As paper burns, paper molecules react with oxygen molecules in the air. This reaction breaks the chemical bonds in the molecules. The atoms then link together in a different way to form different molecules. For example, carbon dioxide molecules are formed when paper burns.
In a physical change, chemical bonds do not break. The types of molecules in matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, water vaporizing is a physical change that can be caused by heating. Liquid water and water vapor are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
Snails growing shells is a chemical change. A snail's body uses calcium from its food to make a new molecule called calcium carbonate. This calcium carbonate is used to grow the shell.
Photosynthesis is a chemical change. Plants make sugar using carbon dioxide, water, and energy from sunlight.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are chemical changes. They are not physical changes.
Both are chemical changes.
Both changes are chemical changes. The type of matter before and after each change is different.
Both are caused by heating.
Neither change is caused by heating.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: Select the reptile.

Choices:
A. Nile crocodile
B. salmon
C. green frog
D. olive toad

Reptiles have scaly, waterproof skin. Most reptiles live on land.

An olive toad is an amphibian. It has moist skin and begins its life in water.
Toads do not have teeth! They swallow their food whole.
A green frog is an amphibian. It has moist skin and begins its life in water.
Frogs live near water or in damp places. Most frogs lay their eggs in water.
A salmon is a fish. It lives underwater. It has fins, not limbs.
Unlike most other fish, salmon can live in both fresh water and salt water.
A Nile crocodile is a reptile. It has scaly, waterproof skin.
Crocodiles hunt their prey in or near water.

natural science


Question:
What do these two changes have in common?
mixing sand and gravel
crushing a mineral into powder

Choices:
A. Both are caused by cooling.
B. Both are only physical changes.
C. Both are caused by heating.
D. Both are chemical changes.

Chemical changes and physical changes are two common ways matter can change.
In a chemical change, the type of matter changes. The types of matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. When paper gets hot enough, it reacts with oxygen in the air and burns. The paper and oxygen change into ash and smoke.
In a physical change, the type of matter stays the same. The types of matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, ice melting is a physical change that can be caused by heating. Ice and liquid water are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
Mixing sand and gravel is a physical change. Together, the sand and gravel make a mixture. But making this mixture does not form a different type of matter.
Crushing a mineral into powder is a physical change. The mineral breaks into tiny pieces. But it is still made of the same type of matter.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are physical changes. No new matter is created.
Both are chemical changes.
Both changes are physical changes. They are not chemical changes.
Both are caused by heating.
Neither change is caused by heating.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: What is the expected ratio of offspring with yellow fruit to offspring with red fruit? Choose the most likely ratio.

Choices:
A. 1:3
B. 2:2
C. 0:4
D. 3:1
E. 4:0

In a group of tomato plants, some individuals have red fruit and others have yellow fruit. In this group, the gene for the fruit color trait has two alleles. The allele for red fruit (F) is dominant over the allele for yellow fruit (f).
This Punnett square shows a cross between two tomato plants.

Offspring phenotypes: dominant or recessive?
How do you determine an organism's phenotype for a trait? Look at the combination of alleles in the organism's genotype for the gene that affects that trait. Some alleles have types called dominant and recessive. These two types can cause different versions of the trait to appear as the organism's phenotype.
If an organism's genotype has at least one dominant allele for a gene, the organism's phenotype will be the dominant allele's version of the gene's trait.
If an organism's genotype has only recessive alleles for a gene, the organism's phenotype will be the recessive allele's version of the gene's trait.
A Punnett square shows what types of offspring a cross can produce. The expected ratio of offspring types compares how often the cross produces each type of offspring, on average. To write this ratio, count the number of boxes in the Punnett square representing each type.
For example, consider the Punnett square below.
 | F | f
F | FF | Ff
f | Ff | ff
There is 1 box with the genotype FF and 2 boxes with the genotype Ff. So, the expected ratio of offspring with the genotype FF to those with Ff is 1:2.

To determine how many boxes in the Punnett square represent offspring with yellow fruit or red fruit, consider whether each phenotype is the dominant or recessive allele's version of the fruit color trait. The question tells you that the F allele, which is for red fruit, is dominant over the f allele, which is for yellow fruit.
Yellow fruit is the recessive allele's version of the fruit color trait. A tomato plant with the recessive version of the fruit color trait must have only recessive alleles for the fruit color gene. So, offspring with yellow fruit must have the genotype ff.
All 4 boxes in the Punnett square have the genotype ff.
Red fruit is the dominant allele's version of the fruit color trait. A tomato plant with the dominant version of the fruit color trait must have at least one dominant allele for the fruit color gene. So, offspring with red fruit must have the genotype FF or Ff.
There are 0 boxes in the Punnett square with the genotype FF or Ff.
So, the expected ratio of offspring with yellow fruit to offspring with red fruit is 4:0. This means that, based on the Punnett square, this cross will always produce offspring with yellow fruit. This cross is expected to never produce offspring with red fruit.

natural science


Question:
What do these two changes have in common?
a puddle freezing into ice on a cold night
beating an egg

Choices:
A. Both are only physical changes.
B. Both are chemical changes.
C. Both are caused by cooling.
D. Both are caused by heating.

Matter is made of very small particles called atoms. Atoms can be linked together by chemical bonds. When two or more atoms link together, they form a molecule.
In a chemical change, the chemical bonds in the molecules break. The atoms then link together to form different molecules. The types of molecules in matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. As paper burns, paper molecules react with oxygen molecules in the air. This reaction breaks the chemical bonds in the molecules. The atoms then link together in a different way to form different molecules. For example, carbon dioxide molecules are formed when paper burns.
In a physical change, chemical bonds do not break. The types of molecules in matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, water vaporizing is a physical change that can be caused by heating. Liquid water and water vapor are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
A puddle freezing into ice on a cold night is a change of state. So, it is a physical change. Liquid water freezes and becomes solid, but it is still made of water. A different type of matter is not formed.
Beating an egg is a physical change. Beating an egg mixes together the egg white, egg yolk, and some air. But mixing them together does not form a different type of matter.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are physical changes. No new matter is created.
Both are chemical changes.
Both changes are physical changes. They are not chemical changes.
Both are caused by heating.
Neither change is caused by heating.
Both are caused by cooling.
A puddle freezing is caused by cooling. But beating an egg is not.

natural science


Question: Select the mammal below.

Choices:
A. box turtle
B. human
C. common toad
D. clownfish

Mammals have hair or fur and feed their young milk.
Mammals are warm-blooded. Warm-blooded animals can control their body temperature.
A koala is an example of a mammal.

Birds, mammals, fish, reptiles, and amphibians are groups of animals. Scientists sort animals into each group based on traits they have in common. This process is called classification.
Classification helps scientists learn about how animals live. Classification also helps scientists compare similar animals.

A common toad is an amphibian. It has moist skin and begins its life in water.
Toads do not have teeth! They swallow their food whole.
A box turtle is a reptile. It has scaly, waterproof skin.
Box turtles can live to be over 100 years old!
A clownfish is a fish. It lives underwater. It has fins, not limbs.
Clownfish live with animals called anemones. In the image of the clownfish, you can see the green anemone behind the clownfish.
A human is a mammal. It has hair and feeds its young milk.
Humans are a type of animal called a primate. Monkeys and apes are also primates.

natural science


Question: In this food web, which organism contains matter that eventually moves to the earthworm?

Choices:
A. barren-ground caribou
B. bear sedge
C. mushroom
D. grizzly bear

Below is a food web from a tundra ecosystem in Nunavut, a territory in Northern Canada.
A food web models how the matter eaten by organisms moves through an ecosystem. The arrows in a food web represent how matter moves between organisms in an ecosystem.

A food web is a model.
A food web shows where organisms in an ecosystem get their food. Models can make things in nature easier to understand because models can represent complex things in a simpler way. If a food web showed every organism in an ecosystem, the food web would be hard to understand. So, each food web shows how some organisms in an ecosystem can get their food.
Arrows show how matter moves.
A food web has arrows that point from one organism to another. Each arrow shows the direction that matter moves when one organism eats another organism. An arrow starts from the organism that is eaten. The arrow points to the organism that is doing the eating.
An organism in a food web can have more than one arrow pointing from it. This shows that the organism is eaten by more than one other organism in the food web.
An organism in a food web can also have more than one arrow pointing to it. This shows that the organism eats more than one other organism in the food web.

Use the arrows to follow how matter moves through this food web. For each answer choice, try to find a path of arrows to the earthworm.
The only arrow pointing from the grizzly bear leads to the mushroom. No arrows point from the mushroom to any other organisms. So, in this food web, matter does not move from the grizzly bear to the earthworm.There are three paths matter can take from the bear sedge to the earthworm: bear sedge->brown lemming->Arctic fox->earthworm. bear sedge->brown lemming->snowy owl->earthworm. bear sedge->brown lemming->parasitic jaeger->rough-legged hawk->earthworm. mushroom. No arrows point from the mushroom to any other organisms. So, in this food web, matter does not move from the mushroom to the earthworm.. barren-ground caribou. There are two arrows pointing from the barren-ground caribou to other organisms. One arrow points to the grizzly bear. The only arrow pointing from the grizzly bear leads to the mushroom. The other arrow pointing from the barren-ground caribou leads to the mushroom. No arrows point from the mushroom to any other organisms. So, in this food web, matter does not move from the barren-ground caribou to the earthworm.. There are four paths matter can take from the bilberry to the earthworm: bilberry->Arctic fox->earthworm. bilberry->brown lemming->Arctic fox->earthworm. bilberry->brown lemming->snowy owl->earthworm. bilberry->brown lemming->parasitic jaeger->rough-legged hawk->earthworm.

natural science


Question: Select the invertebrate.

Choices:
A. komodo dragon
B. gray crowned crane
C. mosquito
D. tiger

Hint: Insects, spiders, and worms are invertebrates.

Vertebrates and invertebrates are both groups of animals.
A vertebrate has a backbone. The backbone is made of many bones in an animal's back. A vertebrate's backbone helps connect the different parts of its body. In the drawings below, each vertebrate's backbone is colored orange.
An invertebrate does not have a backbone. In fact, invertebrates do not have any bones! Some invertebrates have an outer cover on their body called an exoskeleton. Other invertebrates have a soft body.

A mosquito is an insect. Like other insects, a mosquito is an invertebrate. It does not have a backbone. It has an exoskeleton.
A tiger is a mammal. Like other mammals, a tiger is a vertebrate. It has a backbone.
A komodo dragon is a reptile. Like other reptiles, a komodo dragon is a vertebrate. It has a backbone.
A gray crowned crane is a bird. Like other birds, a gray crowned crane is a vertebrate. It has a backbone.

natural science


Question: Select the part whose main job is to help a plant cell make proteins.

Choices:
A. mitochondria
B. endoplasmic reticulum
C. cytoplasm
D. cell wall

Plant cells are made up of many different parts. Each cell part has a function that helps the cell survive and grow.
Some cell parts are called organelles. Organelles are cell structures that are surrounded by their own membranes. Here are some of the organelles in plant cells:
Chloroplasts and mitochondria work together to help the cell get the energy it needs. The chloroplasts use photosynthesis to make sugar. The mitochondria break down this sugar and release energy that the cell can use for all of its activities.
The nucleus directs cell activities by sending instructions to different parts of the cell. The nucleus contains structures called chromosomes. The chromosomes are made mostly of hereditary material called DNA. DNA contains information that the cell uses for growth and activities. These instructions tell ribosomes how to build molecules called proteins, which make up cell structures and help chemical reactions happen in the cell.
The endoplasmic reticulum is an organelle that helps ribosomes build proteins. The nucleus sends instructions for making proteins to ribosomes. Ribosomes can attach to the endoplamic reticulum. The endoplasmic reticulum and ribosomes use these instructions to make proteins that the cell needs to survive and grow.
After proteins are made in the endoplasmic reticulum, they can be transferred to the Golgi. The Golgi is an organelle made up of flat, stacked membranes. The Golgi sorts and packages proteins and other substances. Then, the Golgi sends these substances to different parts of the cell. Some of these substances are sent to the cell membrane and released from the cell.
In plant cells, the vacuole stores waste, water, and nutrients such as sugar. Most plant cells have one vacuole.
Other cell parts are not surrounded by their own membranes. These cell parts are not organelles.
The cell wall is the cell's tough outer covering. It gives the cell strength and stiffness and helps the cell keep its shape.
On the inside of the cell wall is a thin layer called the cell membrane. This layer is a membrane, but it does not have a membrane surrounding it, so it is not an organelle. The cell membrane controls which substances enter and leave the cell.
The cytoplasm is a thick liquid that fills the space inside the cell. The cytoplasm also helps the cell keep its shape and supports the other cell parts.

The endoplasmic reticulum helps the cell make proteins. Instructions for making proteins are sent to ribosomes. Ribosomes can attach to the endoplamic reticulum and use the instructions to make proteins.

natural science


Question: Select the part that contains the information that a plant cell uses for growth and activities.

Choices:
A. mitochondria
B. chloroplasts
C. Golgi
D. chromosomes

Plant cells are made up of many different parts. Each cell part has a function that helps the cell survive and grow.
Some cell parts are called organelles. Organelles are cell structures that are surrounded by their own membranes. Here are some of the organelles in plant cells:
Chloroplasts and mitochondria work together to help the cell get the energy it needs. The chloroplasts use photosynthesis to make sugar. The mitochondria break down this sugar and release energy that the cell can use for all of its activities.
The nucleus directs cell activities by sending instructions to different parts of the cell. The nucleus contains structures called chromosomes. The chromosomes are made mostly of hereditary material called DNA. DNA contains information that the cell uses for growth and activities. These instructions tell ribosomes how to build molecules called proteins, which make up cell structures and help chemical reactions happen in the cell.
The endoplasmic reticulum is an organelle that helps ribosomes build proteins. The nucleus sends instructions for making proteins to ribosomes. Ribosomes can attach to the endoplamic reticulum. The endoplasmic reticulum and ribosomes use these instructions to make proteins that the cell needs to survive and grow.
After proteins are made in the endoplasmic reticulum, they can be transferred to the Golgi. The Golgi is an organelle made up of flat, stacked membranes. The Golgi sorts and packages proteins and other substances. Then, the Golgi sends these substances to different parts of the cell. Some of these substances are sent to the cell membrane and released from the cell.
In plant cells, the vacuole stores waste, water, and nutrients such as sugar. Most plant cells have one vacuole.
Other cell parts are not surrounded by their own membranes. These cell parts are not organelles.
The cell wall is the cell's tough outer covering. It gives the cell strength and stiffness and helps the cell keep its shape.
On the inside of the cell wall is a thin layer called the cell membrane. This layer is a membrane, but it does not have a membrane surrounding it, so it is not an organelle. The cell membrane controls which substances enter and leave the cell.
The cytoplasm is a thick liquid that fills the space inside the cell. The cytoplasm also helps the cell keep its shape and supports the other cell parts.

Chromosomes contain the information that the cell uses for growth and activities. This information helps control what the cell does and how it grows and develops.
In plant and animal cells, the chromosomes are inside the nucleus.

natural science


Question:
What do these two changes have in common?
using polish to remove tarnish from a silver spoon
a piece of avocado turning brown

Choices:
A. Both are caused by heating.
B. Both are caused by cooling.
C. Both are only physical changes.
D. Both are chemical changes.

Matter is made of very small particles called atoms. Atoms can be linked together by chemical bonds. When two or more atoms link together, they form a molecule.
In a chemical change, the chemical bonds in the molecules break. The atoms then link together to form different molecules. The types of molecules in matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. As paper burns, paper molecules react with oxygen molecules in the air. This reaction breaks the chemical bonds in the molecules. The atoms then link together in a different way to form different molecules. For example, carbon dioxide molecules are formed when paper burns.
In a physical change, chemical bonds do not break. The types of molecules in matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, water vaporizing is a physical change that can be caused by heating. Liquid water and water vapor are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
A tarnished silver spoon is one that has become less shiny over time. Polishing the spoon makes it look shiny again.
The polish changes the tarnish into a different type of matter that can be easily wiped away. So, using polish to remove tarnish from silver is a chemical change.
A piece of avocado turning brown is a chemical change. The avocado reacts with oxygen in the air to form a different type of matter.
If you scrape off the brown part of the avocado, the inside will still be green. The inside hasn't touched the air. So the chemical change hasn't happened to that part of the avocado.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are chemical changes. They are not physical changes.
Both are chemical changes.
Both changes are chemical changes. The type of matter before and after each change is different.
Both are caused by heating.
Neither change is caused by heating.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: What is the expected ratio of offspring with mutated antennae to offspring with normal antennae? Choose the most likely ratio.

Choices:
A. 1:3
B. 2:2
C. 3:1
D. 4:0
E. 0:4

This passage describes the antenna type trait in fruit flies:
Most fruit flies have a pair of antennae on their head. But, some flies appear to have an extra pair of legs on their head instead! These flies have a mutation, or change, in a gene that affects body development. This mutation makes the cells in the fly's head form mutated antennae that are like legs.
In a group of fruit flies, some individuals have mutated antennae and others have normal antennae. In this group, the gene for the antenna type trait has two alleles. The allele for mutated antennae (A) is dominant over the allele for normal antennae (a).
This Punnett square shows a cross between two fruit flies.

Offspring phenotypes: dominant or recessive?
How do you determine an organism's phenotype for a trait? Look at the combination of alleles in the organism's genotype for the gene that affects that trait. Some alleles have types called dominant and recessive. These two types can cause different versions of the trait to appear as the organism's phenotype.
If an organism's genotype has at least one dominant allele for a gene, the organism's phenotype will be the dominant allele's version of the gene's trait.
If an organism's genotype has only recessive alleles for a gene, the organism's phenotype will be the recessive allele's version of the gene's trait.
A Punnett square shows what types of offspring a cross can produce. The expected ratio of offspring types compares how often the cross produces each type of offspring, on average. To write this ratio, count the number of boxes in the Punnett square representing each type.
For example, consider the Punnett square below.
 | F | f
F | FF | Ff
f | Ff | ff
There is 1 box with the genotype FF and 2 boxes with the genotype Ff. So, the expected ratio of offspring with the genotype FF to those with Ff is 1:2.

To determine how many boxes in the Punnett square represent offspring with mutated antennae or normal antennae, consider whether each phenotype is the dominant or recessive allele's version of the antenna type trait. The question tells you that the A allele, which is for mutated antennae, is dominant over the a allele, which is for normal antennae.
Mutated antennae is the dominant allele's version of the antenna type trait. A fruit fly with the dominant version of the antenna type trait must have at least one dominant allele for the antenna type gene. So, offspring with mutated antennae must have the genotype AA or Aa.
There are 3 boxes in the Punnett square with the genotype AA or Aa. These boxes are highlighted below.
Normal antennae is the recessive allele's version of the antenna type trait. A fruit fly with the recessive version of the antenna type trait must have only recessive alleles for the antenna type gene. So, offspring with normal antennae must have the genotype aa.
There is 1 box in the Punnett square with the genotype aa. This box is highlighted below.
So, the expected ratio of offspring with mutated antennae to offspring with normal antennae is 3:1. This means that, on average, this cross will produce 3 offspring with mutated antennae for every 1 offspring with normal antennae.

natural science


Question: Select the vertebrate.

Choices:
A. dung beetle
B. curlyhair tarantula
C. rainbow boa
D. monarch butterfly

Hint: Mammals, birds, fish, reptiles, and amphibians are vertebrates.

Vertebrates and invertebrates are both groups of animals.
A vertebrate has a backbone. The backbone is made of many bones in an animal's back. A vertebrate's backbone helps connect the different parts of its body. In the drawings below, each vertebrate's backbone is colored orange.
An invertebrate does not have a backbone. In fact, invertebrates do not have any bones! Some invertebrates have an outer cover on their body called an exoskeleton. Other invertebrates have a soft body.

A monarch butterfly is an insect. Like other insects, a monarch butterfly is an invertebrate. It does not have a backbone. It has an exoskeleton.
A rainbow boa is a reptile. Like other reptiles, a rainbow boa is a vertebrate. It has a backbone.
A dung beetle is an insect. Like other insects, a dung beetle is an invertebrate. It does not have a backbone. It has an exoskeleton.
Like other tarantulas, a curlyhair tarantula is an invertebrate. It does not have a backbone. It has an exoskeleton.

natural science


Question: How long is a potato?

Choices:
A. 16 kilometers
B. 16 centimeters
C. 16 meters
D. 16 millimeters

Select the best estimate.

Measurements are written with both a number and a unit. The unit comes after the number. The unit shows what the number means.
When you are using metric units, length can be written with units of millimeters, centimeters, meters, or kilometers. One meter contains 100 centimeters or 1,000 millimeters. So, 1 meter is larger than 1 centimeter, and 1 centimeter is larger than 1 millimeter.
The tip of the pencil shown here is only 1 millimeter wide, but the pencil is about 16 centimeters long.
A red fox is about 1 meter long. The Sydney Harbour Bridge in Australia is about 1,000 meters, or 1 kilometer, in length.

The best estimate for the length of a potato is 16 centimeters.
16 millimeters is too short. 16 meters and 16 kilometers are too long.

natural science


Question: Select the bird.

Choices:
A. red-eyed tree frog
B. harbor seal
C. humpback whale
D. Steller's sea eagle

Birds have feathers, two wings, and a beak.

A humpback whale is a mammal. It has hair and feeds its young milk.
Whales are mammals that live in the ocean. Humpback whales have small hairs that grow from bumps around their mouth.
A red-eyed tree frog is an amphibian. It has moist skin and begins its life in water.
A red-eyed tree frog has sticky pads on its toes. The sticky pads help the red-eyed tree frog hold on to leaves.
A harbor seal is a mammal. It has fur and feeds its young milk.
Seals have flippers instead of arms! They use their flippers to swim underwater or to crawl on the beach.
A Steller's sea eagle is a bird. It has feathers, two wings, and a beak.
Sea eagles use their sharp beaks to eat fish and other birds.

natural science


Question:
What do these two changes have in common?
sewing an apron
mixing lettuce and salad dressing

Choices:
A. Both are caused by cooling.
B. Both are only physical changes.
C. Both are caused by heating.
D. Both are chemical changes.

Matter is made of very small particles called atoms. Atoms can be linked together by chemical bonds. When two or more atoms link together, they form a molecule.
In a chemical change, the chemical bonds in the molecules break. The atoms then link together to form different molecules. The types of molecules in matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. As paper burns, paper molecules react with oxygen molecules in the air. This reaction breaks the chemical bonds in the molecules. The atoms then link together in a different way to form different molecules. For example, carbon dioxide molecules are formed when paper burns.
In a physical change, chemical bonds do not break. The types of molecules in matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, water vaporizing is a physical change that can be caused by heating. Liquid water and water vapor are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
Sewing an apron is a physical change. The fabric and thread that make up the apron get a new shape, but the type of matter in each of them does not change.
Mixing lettuce and salad dressing is a physical change. Together, the salad and dressing make a mixture. But making this mixture does not form a different type of matter.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are physical changes. No new matter is created.
Both are chemical changes.
Both changes are physical changes. They are not chemical changes.
Both are caused by heating.
Neither change is caused by heating.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: How long is a soccer field?

Choices:
A. 390 feet
B. 390 yards
C. 390 miles
D. 390 inches

Select the best estimate.

Measurements are written with both a number and a unit. The unit comes after the number. The unit shows what the number means.
When you are using customary units, length may be written with units of inches, feet, yards, or miles.
There are 12 inches in 1 foot, and 3 feet in 1 yard. There are 5,280 feet in 1 mile.
A football is about 1 foot long. A football field is 100 yards long.

The best estimate for the length of a soccer field is 390 feet.
390 inches is too short. 390 yards and 390 miles are too long.

natural science


Question: What is the expected ratio of offspring with dumbo ears to offspring with normal ears? Choose the most likely ratio.

Choices:
A. 4:0
B. 0:4
C. 2:2
D. 3:1
E. 1:3

This passage describes the ear type trait in rats:
Some rats have dumbo ears, which are larger and rounder than normal ears. Dumbo ears are also set on the sides of the rat's head instead of on the top. The word dumbo comes from the name of a cartoon elephant whose ears had a similar appearance.
In a group of rats, some individuals have normal ears and others have dumbo ears. In this group, the gene for the ear type trait has two alleles. The allele for normal ears (E) is dominant over the allele for dumbo ears (e).
This Punnett square shows a cross between two rats.

Offspring phenotypes: dominant or recessive?
How do you determine an organism's phenotype for a trait? Look at the combination of alleles in the organism's genotype for the gene that affects that trait. Some alleles have types called dominant and recessive. These two types can cause different versions of the trait to appear as the organism's phenotype.
If an organism's genotype has at least one dominant allele for a gene, the organism's phenotype will be the dominant allele's version of the gene's trait.
If an organism's genotype has only recessive alleles for a gene, the organism's phenotype will be the recessive allele's version of the gene's trait.
A Punnett square shows what types of offspring a cross can produce. The expected ratio of offspring types compares how often the cross produces each type of offspring, on average. To write this ratio, count the number of boxes in the Punnett square representing each type.
For example, consider the Punnett square below.
 | F | f
F | FF | Ff
f | Ff | ff
There is 1 box with the genotype FF and 2 boxes with the genotype Ff. So, the expected ratio of offspring with the genotype FF to those with Ff is 1:2.

To determine how many boxes in the Punnett square represent offspring with dumbo ears or normal ears, consider whether each phenotype is the dominant or recessive allele's version of the ear type trait. The question tells you that the E allele, which is for normal ears, is dominant over the e allele, which is for dumbo ears.
Dumbo ears is the recessive allele's version of the ear type trait. A rat with the recessive version of the ear type trait must have only recessive alleles for the ear type gene. So, offspring with dumbo ears must have the genotype ee.
There are 0 boxes in the Punnett square with the genotype ee.
Normal ears is the dominant allele's version of the ear type trait. A rat with the dominant version of the ear type trait must have at least one dominant allele for the ear type gene. So, offspring with normal ears must have the genotype EE or Ee.
All 4 boxes in the Punnett square have the genotype EE or Ee.
So, the expected ratio of offspring with dumbo ears to offspring with normal ears is 0:4. This means that, based on the Punnett square, this cross will never produce offspring with dumbo ears. Instead, this cross is expected to always produce offspring with normal ears.

natural science


Question: Select the vertebrate.

Choices:
A. peacock butterfly
B. bess beetle
C. snowy owl
D. Caribbean spiny lobster

Hint: Mammals, birds, fish, reptiles, and amphibians are vertebrates.

Vertebrates and invertebrates are both groups of animals.
A vertebrate has a backbone. The backbone is made of many bones in an animal's back. A vertebrate's backbone helps connect the different parts of its body. In the drawings below, each vertebrate's backbone is colored orange.
An invertebrate does not have a backbone. In fact, invertebrates do not have any bones! Some invertebrates have an outer cover on their body called an exoskeleton. Other invertebrates have a soft body.

A bess beetle is an insect. Like other insects, a bess beetle is an invertebrate. It does not have a backbone. It has an exoskeleton.
A Caribbean spiny lobster is a crustacean. Like other crustaceans, a Caribbean spiny lobster is an invertebrate. It does not have a backbone. It has an exoskeleton.
A snowy owl is a bird. Like other birds, a snowy owl is a vertebrate. It has a backbone.
A peacock butterfly is an insect. Like other insects, a peacock butterfly is an invertebrate. It does not have a backbone. It has an exoskeleton.

natural science


Question: Select the plant.

Choices:
A. Salmon swim in the water.
B. Peregrine falcons walk and fly.
C. Banana trees have large leaves.
D. Koalas eat leaves.

Plants and animals are living things. Living things are called organisms.
Plants come in many shapes and sizes. Most plants grow in the ground. They might grow leaves, flowers, and fruit. Plants cannot move around on their own like animals can.
Animals also come in many shapes and sizes. Most animals can move around. Animals might run, swim, jump, or fly. Animals eat plants or other organisms for food.

A peregrine falcon is an animal. It walks and flies.
A peregrine falcon can fly very fast. It is the fastest animal in the world!
A salmon is an animal. It swims in the water.
Unlike most other fish, salmon can live in both freshwater and seawater.
A koala is an animal. It eats leaves.
Koalas spend most of their time in trees. They sleep for up to 20 hours a day!
A banana tree is a plant. It has large leaves.
The leaves on a banana tree can be up to nine feet long!

natural science


Question: Select the liquid.

Choices:
A. helium
B. rain
C. umbrella
D. plate

Solid, liquid, and gas are states of matter. Matter is anything that takes up space. Matter can come in different states, or forms.
When matter is a solid, it has a definite volume and a definite shape. So, a solid has a size and shape of its own.
Some solids can be easily folded, bent, or broken. A piece of paper is a solid. Also, some solids are very small. A grain of sand is a solid.
When matter is a liquid, it has a definite volume but not a definite shape. So, a liquid has a size of its own, but it does not have a shape of its own. Think about pouring juice from a bottle into a cup. The juice still takes up the same amount of space, but it takes the shape of the bottle.
Some liquids do not pour as easily as others. Honey and milk are both liquids. But pouring honey takes more time than pouring milk.
When matter is a gas, it does not have a definite volume or a definite shape. A gas expands, or gets bigger, until it completely fills a space. A gas can also get smaller if it is squeezed into a smaller space.
Many gases are invisible. Air is a gas.

Rain is a liquid. A liquid takes the shape of any container it is in. If you put rainwater into a bucket, the rainwater will take the shape of the bucket. But the rainwater will still take up the same amount of space.
A plate is a solid. If someone drops a plate, it may break into pieces. But each piece will still have a size and shape of its own.
An umbrella is a solid. A solid has a size and shape of its own. When you open an umbrella, it still has a size and shape of its own.
Helium is a gas. A gas expands to fill a space. Helium is lighter than air. So, if you fill a balloon with helium, the balloon will rise. If helium leaks out of the balloon, the helium will expand into the space around the balloon.

natural science


Question: Select the liquid.

Choices:
A. rag doll
B. arrowhead
C. vinegar
D. eraser

Solid, liquid, and gas are states of matter. Matter is anything that takes up space. Matter can come in different states, or forms.
When matter is a solid, it has a definite volume and a definite shape. So, a solid has a size and shape of its own.
Some solids can be easily folded, bent, or broken. A piece of paper is a solid. Also, some solids are very small. A grain of sand is a solid.
When matter is a liquid, it has a definite volume but not a definite shape. So, a liquid has a size of its own, but it does not have a shape of its own. Think about pouring juice from a bottle into a cup. The juice still takes up the same amount of space, but it takes the shape of the bottle.
Some liquids do not pour as easily as others. Honey and milk are both liquids. But pouring honey takes more time than pouring milk.
When matter is a gas, it does not have a definite volume or a definite shape. A gas expands, or gets bigger, until it completely fills a space. A gas can also get smaller if it is squeezed into a smaller space.
Many gases are invisible. Air is a gas.

An arrowhead is a solid. A solid has a size and shape of its own. An arrowhead is made of rock.
An eraser is a solid. You can bend an eraser. But it will still have a size and shape of its own.
Vinegar is a liquid. A liquid takes the shape of any container it is in. If you pour vinegar into a different container, the vinegar will take the shape of that container. But the vinegar will still take up the same amount of space.
A rag doll is a solid. A solid has a size and shape of its own. When you hold a rag doll in your hands, the rag doll still has a size and shape of its own.

natural science


Question: What is the probability that a fruit fly produced by this cross will have normal wings?

Choices:
A. 1/4
B. 2/4
C. 0/4
D. 3/4
E. 4/4

This passage describes the wing type trait in fruit flies:
Some scientists breed fruit flies to learn how traits are inherited. These scientists often use flies with vestigial wings, which are shorter and stubbier than normal wings. Fruit flies with vestigial wings cannot fly, so they are easier for scientists to handle and study.
In a group of fruit flies, some individuals have normal wings and others have vestigial wings. In this group, the gene for the wing type trait has two alleles. The allele for vestigial wings (n) is recessive to the allele for normal wings (N).
This Punnett square shows a cross between two fruit flies.

Offspring phenotypes: dominant or recessive?
How do you determine an organism's phenotype for a trait? Look at the combination of alleles in the organism's genotype for the gene that affects that trait. Some alleles have types called dominant and recessive. These two types can cause different versions of the trait to appear as the organism's phenotype.
If an organism's genotype has at least one dominant allele for a gene, the organism's phenotype will be the dominant allele's version of the gene's trait.
If an organism's genotype has only recessive alleles for a gene, the organism's phenotype will be the recessive allele's version of the gene's trait.
In a Punnett square, each box represents a different outcome, or result. Each of the four outcomes is equally likely to happen. Each box represents one way the parents' alleles can combine to form an offspring's genotype. Because there are four boxes in the Punnett square, there are four possible outcomes.
An event is a set of one or more outcomes. The probability of an event is a measure of how likely the event is to happen. This probability is a number between 0 and 1, and it can be written as a fraction:
probability of an event = number of ways the event can happen / number of equally likely outcomes
You can use a Punnett square to calculate the probability that a cross will produce certain offspring. For example, the Punnett square below has two boxes with the genotype Ff. It has one box with the genotype FF and one box with the genotype ff. This means there are two ways the parents' alleles can combine to form Ff. There is one way they can combine to form FF and one way they can combine to form ff.
 | F | f
F | FF | Ff
f | Ff | ff
Consider an event in which this cross produces an offspring with the genotype ff. The probability of this event is given by the following fraction:
number of ways the event can happen / number of equally likely outcomes = number of boxes with the genotype ff / total number of boxes = 1 / 4.

natural science

Use Punnett squares to calculate probabilities of offspring types


Question: Select the bird below.

Choices:
A. ocean sunfish
B. common toad
C. water buffalo
D. penguin

Birds have feathers, two wings, and a beak.
Birds are warm-blooded. Warm-blooded animals can control their body temperature.
A bald eagle is an example of a bird.

Birds, mammals, fish, reptiles, and amphibians are groups of animals. Scientists sort animals into each group based on traits they have in common. This process is called classification.
Classification helps scientists learn about how animals live. Classification also helps scientists compare similar animals.

A penguin is a bird. It has feathers, two wings, and a beak.
Penguins live near water. Penguins cannot fly! They use their wings to swim.
A water buffalo is a mammal. It has hair and feeds its young milk.
Water buffaloes live in Asia. Some people raise water buffaloes for their milk.
A common toad is an amphibian. It has moist skin and begins its life in water.
Toads do not have teeth! They swallow their food whole.
An ocean sunfish is a fish. It lives underwater. It has fins, not limbs.
Ocean sunfish have a flat body and wide fins. They sometimes swim to the ocean's surface to rest in the sun.

natural science


Question: What is the probability that a budgerigar parakeet produced by this cross will be heterozygous for the body feather color gene?

Choices:
A. 2/4
B. 0/4
C. 1/4
D. 3/4
E. 4/4

In a group of budgerigar parakeets, some individuals have green body feathers and others have blue body feathers. In this group, the gene for the body feather color trait has two alleles. The allele for green body feathers (B) is dominant over the allele for blue body feathers (b).
This Punnett square shows a cross between two budgerigar parakeets.

Offspring genotypes: homozygous or heterozygous?
How do you determine whether an organism is homozygous or heterozygous for a gene? Look at the alleles in the organism's genotype for that gene.
An organism with two identical alleles for a gene is homozygous for that gene.
If both alleles are dominant, the organism is homozygous dominant for the gene.
If both alleles are recessive, the organism is homozygous recessive for the gene.
An organism with two different alleles for a gene is heterozygous for that gene.
In a Punnett square, each box represents a different outcome, or result. Each of the four outcomes is equally likely to happen. Each box represents one way the parents' alleles can combine to form an offspring's genotype.
Because there are four boxes in the Punnett square, there are four possible outcomes.
An event is a set of one or more outcomes. The probability of an event is a measure of how likely the event is to happen. This probability is a number between 0 and 1, and it can be written as a fraction:
probability of an event = number of ways the event can happen / number of equally likely outcomes
You can use a Punnett square to calculate the probability that a cross will produce certain offspring. For example, the Punnett square below has two boxes with the genotype Ff. It has one box with the genotype FF and one box with the genotype ff. This means there are two ways the parents' alleles can combine to form Ff. There is one way they can combine to form FF and one way they can combine to form ff.
 | F | f
F | FF | Ff
f | Ff | ff
Consider an event in which this cross produces an offspring with the genotype ff. The probability of this event is given by the following fraction:
number of ways the event can happen / number of equally likely outcomes = number of boxes with the genotype ff / total number of boxes = 1 / 4

natural science


Question:
What do these two changes have in common?
water evaporating from a puddle
rain forming in a cloud

Choices:
A. Both are only physical changes.
B. Both are caused by heating.
C. Both are chemical changes.
D. Both are caused by cooling.

Matter is made of very small particles called atoms. Atoms can be linked together by chemical bonds. When two or more atoms link together, they form a molecule.
In a chemical change, the chemical bonds in the molecules break. The atoms then link together to form different molecules. The types of molecules in matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. As paper burns, paper molecules react with oxygen molecules in the air. This reaction breaks the chemical bonds in the molecules. The atoms then link together in a different way to form different molecules. For example, carbon dioxide molecules are formed when paper burns.
In a physical change, chemical bonds do not break. The types of molecules in matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, water vaporizing is a physical change that can be caused by heating. Liquid water and water vapor are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
Water evaporating from a puddle is a change of state. So, it is a physical change. The liquid changes into a gas, but a different type of matter is not formed.
Rain forming in a cloud is a change of state. So, it is a physical change. Water vapor in the air condenses into tiny droplets of liquid water. These droplets make up a cloud. When there is enough water in the air, the droplets will fall as rain.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are physical changes. No new matter is created.
Both are chemical changes.
Both changes are physical changes. They are not chemical changes.
Both are caused by heating.
Water evaporating is caused by heating. But rain forming in a cloud is not.
Both are caused by cooling.
Rain begins to form when water vapor in the air becomes liquid water. This is caused by cooling. But water evaporating from a puddle is not.

natural science


Question:
What do these two changes have in common?
cutting a piece of rope
peeling a banana

Choices:
A. Both are chemical changes.
B. Both are caused by cooling.
C. Both are caused by heating.
D. Both are only physical changes.

Chemical changes and physical changes are two common ways matter can change.
In a chemical change, the type of matter changes. The types of matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. When paper gets hot enough, it reacts with oxygen in the air and burns. The paper and oxygen change into ash and smoke.
In a physical change, the type of matter stays the same. The types of matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, ice melting is a physical change that can be caused by heating. Ice and liquid water are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
Cutting a piece of rope is a physical change. The rope is shorter after you cut it. But it is still made of the same type of matter as the uncut rope.
Peeling a banana is a physical change. The peel is not covering the rest of the fruit anymore. But both the peel and the banana are still made of the same type of matter as before.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are physical changes. No new matter is created.
Both are chemical changes.
Both changes are physical changes. They are not chemical changes.
Both are caused by heating.
Neither change is caused by heating.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: Select the fish.

Choices:
A. green iguana
B. Asian elephant
C. red kangaroo
D. bull shark

Fish live underwater. They have fins, not limbs.

A green iguana is a reptile. It has scaly, waterproof skin.
Iguanas are a type of lizard. Iguanas eat plants and fruit.
A bull shark is a fish. It lives underwater. It has fins, not limbs.
Bull sharks can live in both fresh and salt water. They are found in rivers and in shallow parts of the ocean.
A red kangaroo is a mammal. It has fur and feeds its young milk.
Kangaroos hop to move around. They use their large tails for balance while hopping.
An Asian elephant is a mammal. It has hair and feeds its young milk.
Elephants live in groups called herds. The oldest female in the herd is usually the leader.

natural science


Question: Select the mammal below.

Choices:
A. water buffalo
B. woodpecker
C. red-headed poison frog
D. hammerhead shark

Mammals have hair or fur and feed their young milk.
Mammals are warm-blooded. Warm-blooded animals can control their body temperature.
A sea otter is an example of a mammal.

Birds, mammals, fish, reptiles, and amphibians are groups of animals. Scientists sort animals into each group based on traits they have in common. This process is called classification.
Classification helps scientists learn about how animals live. Classification also helps scientists compare similar animals.

A red-headed poison frog is an amphibian. It has moist skin and begins its life in water.
Poison dart frogs come in many bright colors. Their bright color warns other animals that these frogs are poisonous.
A woodpecker is a bird. It has feathers, two wings, and a beak.
Woodpeckers have strong beaks. They use their beaks to drill into wood to hunt for food.
A water buffalo is a mammal. It has hair and feeds its young milk.
Water buffaloes live in Asia. Some people raise water buffaloes for their milk.
A hammerhead shark is a fish. It lives underwater. It has fins, not limbs.
Hammerhead sharks get their names from the shape of their heads. They have a wide, flat head and a small mouth.

natural science


Question:
What do these two changes have in common?
cooking an egg
a penny tarnishing

Choices:
A. Both are caused by cooling.
B. Both are only physical changes.
C. Both are chemical changes.
D. Both are caused by heating.

Chemical changes and physical changes are two common ways matter can change.
In a chemical change, the type of matter changes. The types of matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. When paper gets hot enough, it reacts with oxygen in the air and burns. The paper and oxygen change into ash and smoke.
In a physical change, the type of matter stays the same. The types of matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, ice melting is a physical change that can be caused by heating. Ice and liquid water are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
Cooking an egg is a chemical change. The heat causes the matter in the egg to change. Cooked egg and raw egg are different types of matter.
Metal turning less shiny over time is called tarnishing. A penny tarnishing is a chemical change. When air touches the penny, the surface of the penny changes into a different type of matter. This matter makes the penny dull.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are chemical changes. They are not physical changes.
Both are chemical changes.
Both changes are chemical changes. The type of matter before and after each change is different.
Both are caused by heating.
Cooking is caused by heating. But a penny tarnishing is not.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: How long is a bike path?

Choices:
A. 2 inches
B. 2 miles
C. 2 feet
D. 2 yards

Select the best estimate.

Measurements are written with both a number and a unit. The unit comes after the number. The unit shows what the number means.
When you are using customary units, length may be written with units of inches, feet, yards, or miles.
There are 12 inches in 1 foot, and 3 feet in 1 yard. There are 5,280 feet in 1 mile.
A football is about 1 foot long. A football field is 100 yards long.

The best estimate for the length of a bike path is 2 miles.
2 inches, 2 feet, and 2 yards are all too short.

natural science


Question:
What do these two changes have in common?
erosion caused by wind
beating an egg

Choices:
A. Both are caused by cooling.
B. Both are caused by heating.
C. Both are only physical changes.
D. Both are chemical changes.

Matter is made of very small particles called atoms. Atoms can be linked together by chemical bonds. When two or more atoms link together, they form a molecule.
In a chemical change, the chemical bonds in the molecules break. The atoms then link together to form different molecules. The types of molecules in matter before and after a chemical change are always different.
Some chemical changes are caused by heating or cooling. For example, burning a piece of paper is a chemical change caused by heating. As paper burns, paper molecules react with oxygen molecules in the air. This reaction breaks the chemical bonds in the molecules. The atoms then link together in a different way to form different molecules. For example, carbon dioxide molecules are formed when paper burns.
In a physical change, chemical bonds do not break. The types of molecules in matter before and after a physical change are always the same.
A change of state is a type of physical change. Changes of state can be caused by heating or cooling. For example, water vaporizing is a physical change that can be caused by heating. Liquid water and water vapor are made of the same type of matter: water.
The law of conservation of mass says that all physical and chemical changes conserve mass. Conserve means to keep the same. So, the total mass before a physical or chemical change is equal to the total mass after the change.

Step 1: Think about each change.
Erosion caused by wind is a physical change. The wind carries away tiny pieces of rock. But the pieces of rock do not become a different type of matter.
Beating an egg is a physical change. Beating an egg mixes together the egg white, egg yolk, and some air. But mixing them together does not form a different type of matter.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are physical changes. No new matter is created.
Both are chemical changes.
Both changes are physical changes. They are not chemical changes.
Both are caused by heating.
Neither change is caused by heating.
Both are caused by cooling.
Neither change is caused by cooling.

natural science