Question:
What do these two changes have in common?
bending a paper clip
cutting your fingernails

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.
Bending a paper clip is a physical change. After you bend it, the paper clip has a different shape. But it is still made of the same type of matter.
Cutting your fingernails is a physical change. Your fingernails are shorter after you cut them. But the pieces are still made of the same type of matter as the uncut fingernails.
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 do these two changes have in common?
crushing a mineral into powder
dry ice sublimating and becoming a gas

Choices:
A. Both are caused by cooling.
B. Both are chemical changes.
C. Both are caused by heating.
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.
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.
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 crushing a mineral is not.
Both are caused by cooling.
Neither change is caused by cooling.

natural science

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


Question: Select the reptile.

Choices:
A. ocean sunfish
B. American bullfrog
C. rabbit
D. Mojave rattlesnake

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

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.
A Mojave rattlesnake is a reptile. It has scaly, waterproof skin.
Rattlesnakes have fangs they can use to inject venom into their prey.
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.
An American bullfrog 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.

natural science

Identify mammals, birds, fish, reptiles, and amphibians


Question: Select the chemical formula for this molecule.

Choices:
A. He2S2
B. H3S2
C. H2SN
D. H2S

Every substance around you is made up of atoms. Atoms can link together to form molecules. The links between atoms in a molecule are called chemical bonds. Different molecules are made up of different chemical elements, or types of atoms, bonded together.
Scientists use both ball-and-stick models and chemical formulas to represent molecules.
A ball-and-stick model of a molecule is shown below.
The balls represent atoms. The sticks represent the chemical bonds between the atoms.
Notice how each ball is labeled with a symbol made of one or more letters. The symbol is an abbreviation for a chemical element. The ball represents one atom of that element.
Every chemical element is represented by its own symbol. For some elements, that symbol is one capital letter. For other elements, it is one capital letter followed by one lowercase letter. For example, the symbol for the element boron is B and the symbol for the element chlorine is Cl.
The molecule shown above has one boron atom and three chlorine atoms. A chemical bond links each chlorine atom to the boron atom.
The chemical formula for a molecule contains the symbol for each chemical element in the molecule. Many chemical formulas use subscripts. A subscript is text that is smaller and placed lower than the normal line of text.
In chemical formulas, the subscripts are numbers. The subscript is always written after the symbol for an element. The subscript tells you how many atoms that symbol represents. If the symbol represents just one atom, then no subscript is included.
The symbols in the chemical formula for a molecule match the symbols in the ball-and-stick model for that molecule. The ball-and-stick model shown before and the chemical formula shown above represent the same substance.

H is the symbol for hydrogen. S is the symbol for sulfur. This ball-and-stick model shows a molecule with two hydrogen atoms and one sulfur atom.
The chemical formula will contain the symbols H and S. There are two hydrogen atoms, so H will have a subscript of 2. There is one sulfur atom, so S will not have a subscript.
The correct formula is H2 S.
The diagram below shows how each part of the chemical formula matches with each part of the model above.

natural science

Match chemical formulas to ball-and-stick models


Question: Select the gas.

Choices:
A. tortoise shell
B. pair of dice
C. caramel sauce
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.
A tortoise shell is a solid. A solid has a size and shape of its own. A tortoise shell is made of a solid called keratin, just like your fingernails!
A pair of dice is a solid. A solid has a size and shape of its own. When you roll a pair of dice, the dice have a shape of their own. They are still cubes when they stop rolling.
Caramel sauce is a liquid. A liquid takes the shape of any container it is in. If you pour caramel sauce into a container, the caramel sauce will take the shape of that container. But the caramel sauce will still take up the same amount of space.

natural science


Question: How long is a diving board?

Choices:
A. 10 miles
B. 10 inches
C. 10 feet
D. 10 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 diving board is 10 feet.
10 inches is too short. 10 yards and 10 miles are too long.

natural science

Choose customary units of distance, mass, and volume


Question: Select the liquid.

Choices:
A. tortoise shell
B. plate
C. apple juice
D. gold bracelet

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.

A tortoise shell is a solid. A solid has a size and shape of its own. A tortoise shell is made of a solid called keratin, just like your fingernails!
Apple juice is a liquid. A liquid takes the shape of any container it is in. If you pour apple juice into a different container, the apple juice will take the shape of that container. But the apple juice 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.
A gold bracelet is a solid. You can wrap a gold bracelet around your wrist. But the bracelet will still have a size and shape of its own.

natural science


Question: Select the mammal below.

Choices:
A. bull shark
B. shoebill
C. eastern newt
D. yak

Mammals have hair or fur and feed their young milk.
Mammals are warm-blooded. Warm-blooded animals can control their body temperature.
A giraffe 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 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 shoebill is a bird. It has feathers, two wings, and a beak.
Shoebills live in tropical East Africa. Shoebills get their name from their shoe-shaped beaks.
A yak is a mammal. It has hair and feeds its young milk.
Yaks live in cold places. Their long hair helps keep them warm.
An eastern newt is an amphibian. It has moist skin and begins its life in water.
Some newts live in water. Other newts live on land but lay their eggs in water.

natural science


Question: What is the probability that a sheep produced by this cross will be homozygous dominant for the wool color gene?

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

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

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

Use Punnett squares to calculate probabilities of offspring types


Question: Select the animal.

Choices:
A. Sheep eat plants.
B. Fir trees have green leaves.
C. Chili peppers have green leaves.
D. Tulips have a green stem.

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 fir tree is a plant. It has green leaves.
The leaves of fir trees are called needles.
A chili pepper is a plant. It has many green leaves.
Chili peppers give food a spicy flavor.
A sheep is an animal. It eats plants.
People raise sheep for their fur, meat, and milk.
A tulip is a plant. It has a green stem.
Tulips grow best in cool, dry places.

natural science


Question:
What do these two changes have in common?
cutting an apple
a sidewalk heating up in the sun

Choices:
A. Both are only physical changes.
B. Both are chemical changes.
C. Both are caused by cooling.
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.
Cutting an apple is a physical change. The apple gets a different shape. But it is still made of the same type of matter as the uncut apple.
A sidewalk heating up in the sun is a physical change. The temperature of the sidewalk goes up, but the sidewalk 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.
A sidewalk getting warm in the sun is caused by heating. But cutting an apple is not.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: How long is a hammer?

Choices:
A. 17 centimeters
B. 17 meters
C. 17 kilometers
D. 17 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 hammer is 17 centimeters.
17 millimeters is too short. 17 meters and 17 kilometers are too long.

natural science

Choose metric units of distance, mass, and volume


Question:
What do these two changes have in common?
a piece of avocado turning brown
boiling sugar to make caramel

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.
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.
Boiling sugar to make caramel is a chemical change. The heat causes the sugar to change into a different type of matter. Unlike sugar, the new matter is brown and sticky.
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.
Boiling sugar is caused by heating. But a piece of avocado turning brown is not.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: What is the expected ratio of offspring with white spots to offspring with solid coloring? Choose the most likely ratio.

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

In a group of cows, some individuals have solid coloring and others have white spots. In this group, the gene for the coat pattern trait has two alleles. The allele for white spots (a) is recessive to the allele for solid coloring (A).
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 with white spots or solid coloring, consider whether each phenotype is the dominant or recessive allele's version of the coat pattern trait. The question tells you that the a allele, which is for white spots, is recessive to the A allele, which is for solid coloring.
White spots is the recessive allele's version of the coat pattern trait. A cow with the recessive version of the coat pattern trait must have only recessive alleles for the coat pattern gene. So, offspring with white spots must have the genotype aa.
There are 0 boxes in the Punnett square with the genotype aa.
Solid coloring is the dominant allele's version of the coat pattern trait. A cow with the dominant version of the coat pattern trait must have at least one dominant allele for the coat pattern gene. So, offspring with solid coloring must have the genotype AA or Aa.
All 4 boxes in the Punnett square have the genotype AA or Aa.
So, the expected ratio of offspring with white spots to offspring with solid coloring is 0:4. This means that, based on the Punnett square, this cross will never produce offspring with white spots. Instead, this cross is expected to always produce offspring with solid coloring.

natural science

Use Punnett squares to calculate ratios of offspring types


Question: Select the living thing.

Choices:
A. yeast
B. snowman
C. hockey puck
D. swing set

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 hockey puck is not a living thing.
Hockey pucks 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 yeast is a living thing.
Yeasts grow and respond to their environment. They need food and water.
Each yeast is made up of just one cell. Some types of yeast cells are round. Other yeast cells have a long, thin shape.
A snowman is not a living thing.
A snowman does not have all the traits of a living thing. It is shaped like a person. But it does not need food.
A swing set is not a living thing.
Swing sets 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: Select the fish below.

Choices:
A. seahorse
B. tokay gecko
C. water buffalo
D. western toad

Fish live underwater. They have fins, not limbs.
Fish are cold-blooded. The body temperature of cold-blooded animals depends on their environment.
A Banggai cardinalfish is an example of a fish.

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 tokay gecko is a reptile. It has scaly, waterproof skin.
Many geckos have special pads on their toes. The pads help them climb up plants and rocks.
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 western 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 seahorse is a fish. It lives underwater. It has fins, not limbs.
Seahorses live in shallow, warm water. They can use their tails to hold on to plants.

natural science


Question:
What do these two changes have in common?
shaking up salad dressing
breaking a piece of glass

Choices:
A. Both are caused by heating.
B. Both are chemical changes.
C. Both are caused by cooling.
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.
Shaking up salad dressing is a physical change. The different parts mix together, but they are still made of the same type of matter.
Breaking a piece of glass is a physical change. The glass gets broken into pieces. But each piece 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. air inside a raft
B. hair clip
C. helium
D. water in a fishbowl

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 water in a fishbowl is a liquid. A liquid takes the shape of any container it is in. If you pour water from a fishbowl into a different container, the water will take the shape of that container. But the water will still take up the same amount of space.
A hair clip is a solid. A solid has a size and shape of its own. You can use a hair clip to keep your hair out of your face because the hair clip keeps its shape.
The air inside a raft is a gas. A gas expands to fill a space. The air in a raft expands to fill all the space inside the raft. If air leaks out, it will expand into the space around the raft.
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. chocolate syrup
B. hair clip
C. tortoise shell
D. ballet shoes

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.

A hair clip is a solid. A solid has a size and shape of its own. You can use a hair clip to keep your hair out of your face because the hair clip keeps its shape.
A ballet shoe is a solid. A solid has a size and shape of its own. When a dancer wears a ballet shoe, it may bend a little. But the ballet shoe still has a size and shape of its own.
Chocolate syrup is a liquid. A liquid takes the shape of any container it is in. If you pour chocolate syrup into a container, the chocolate syrup will take the shape of that container. But the chocolate syrup will still take up the same amount of space.
A tortoise shell is a solid. A solid has a size and shape of its own. A tortoise shell is made of a solid called keratin, just like your fingernails!

natural science


Question: Select the solid.

Choices:
A. rain
B. air inside a soccer ball
C. air inside a bubble
D. slide

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.
The air inside a soccer ball is a gas. A gas expands to fill a space. The air fills all the space inside the soccer ball. If air leaks out, it will expand into the space around the ball.
The air inside a bubble is a gas. A gas expands to fill a space. The air inside a bubble fills all the space in the bubble. If the bubble pops, the air will expand to fill a much larger space.
A slide is a solid. A solid has a size and shape of its own. A slide has a size and shape of its own, even when you sit on it.

natural science


Question:
What do these two changes have in common?
water freezing into ice
bending a paper clip

Choices:
A. Both are only physical changes.
B. Both are chemical changes.
C. Both are caused by cooling.
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.
Water freezing into ice is a change of state. So, it is a physical change. The water changes from solid to liquid. But the ice is still made of the same type of matter as the liquid water.
Bending a paper clip is a physical change. After you bend it, the paper clip has a different 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.
Water freezing is caused by cooling. But bending a paper clip is not.

natural science


Question: What is the expected ratio of offspring with a gray body to offspring with a golden body? Choose the most likely ratio.

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

In a group of guppies, some individuals have a gray body and others have a golden body. In this group, the gene for the body color trait has two alleles. The allele for a golden body (b) is recessive to the allele for a gray body (B).
This Punnett square shows a cross between two guppies.

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 gray body or a golden body, consider whether each phenotype is the dominant or recessive allele's version of the body color trait. The question tells you that the b allele, which is for a golden body, is recessive to the B allele, which is for a gray body.
A gray body is the dominant allele's version of the body color trait. A guppy with the dominant version of the body color trait must have at least one dominant allele for the body color gene. So, offspring with a gray body must have the genotype BB or Bb.
There are 3 boxes in the Punnett square with the genotype BB or Bb. These boxes are highlighted below.
A golden body is the recessive allele's version of the body color trait. A guppy with the recessive version of the body color trait must have only recessive alleles for the body color gene. So, offspring with a golden body must have the genotype bb.
There is 1 box in the Punnett square with the genotype bb. This box is highlighted below.
So, the expected ratio of offspring with a gray body to offspring with a golden body is 3:1. This means that, on average, this cross will produce 3 offspring with a gray body for every 1 offspring with a golden body.

natural science


Question: Select the liquid.

Choices:
A. air inside a balloon
B. hammer
C. screwdriver
D. grape juice

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 inside a balloon is a gas. A gas expands to fill a space. The air inside a balloon expands to fill all the space in the balloon. If the balloon pops, the air will expand to fill a much larger space.
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.
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.
A hammer is a solid. A solid has a size and shape of its own. A hammer is made of iron and wood. Both iron and wood are solids.

natural science


Question: Select the fish.

Choices:
A. spotted dolphin
B. ocean sunfish
C. cane toad
D. gray tree frog

Fish live underwater. They have fins, not limbs.

A spotted dolphin is a mammal. It has hair and feeds its young milk.
Dolphins may look like sharks or other fish, but they are mammals! When a baby dolphin is born, it has hair around its jaw. This hair falls out as the dolphin grows.
A gray tree frog is an amphibian. It has moist skin and begins its life in water.
There are many kinds of tree frogs. Most tree frogs are very small. They can walk on thin branches.
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.
A cane toad is an amphibian. It has moist skin and begins its life in water.
Toads do not have teeth! They swallow their food whole.

natural science


Question: How long is a leather belt?

Choices:
A. 30 yards
B. 30 miles
C. 30 feet
D. 30 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 leather belt is 30 inches.
30 feet, 30 yards, and 30 miles are all too long.

natural science


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

Choices:
A. lichen
B. collared lemming
C. earthworm
D. bear sedge

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 bilberry.
No arrow points to the lichen. So, in this food web, matter does not move from the bilberry to the lichen.
No arrow points to the bear sedge. So, in this food web, matter does not move from the bilberry to the bear sedge.
There are two arrows pointing to the collared lemming. One arrow starts from the bear sedge, and the other arrow starts from the lichen. Neither the bear sedge nor the lichen has an arrow pointing to it. So, in this food web, matter does not move from the bilberry to the collared lemming.

natural science


Question: What is the probability that a cockatiel produced by this cross will have bright orange cheeks?

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

In a group of cockatiels, some individuals have bright orange cheeks and others have pale orange cheeks. In this group, the gene for the cheek color trait has two alleles. The allele for bright orange cheeks (R) is dominant over the allele for pale orange cheeks (r).
This Punnett square shows a cross between two cockatiels.

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


Question: How long is a drinking straw?

Choices:
A. 25 meters
B. 25 millimeters
C. 25 centimeters
D. 25 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 drinking straw is 25 centimeters.
25 millimeters is too short. 25 meters and 25 kilometers are too long.

natural science


Question:
What do these two changes have in common?
breaking a plate
cutting your fingernails

Choices:
A. Both are only physical changes.
B. Both are chemical changes.
C. Both are caused by cooling.
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.
Breaking a plate is a physical change. The plate gets broken into pieces. But each piece is still made of the same type of matter.
Cutting your fingernails is a physical change. Your fingernails are shorter after you cut them. But the pieces are still made of the same type of matter as the uncut fingernails.
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 living thing.

Choices:
A. butterfly
B. swing set
C. rain
D. crayon

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.

Rain is not a living thing.
Rain is made of water. It helps living things survive. But it does not have all the traits of a living thing. Rain does not grow or need food.
A butterfly is a living thing.
Butterflies grow and respond to their environment. They need food and water. Butterflies are made up of many cells.
Butterflies are animals. They get their energy from nectar.
A crayon is not a living thing.
Crayons 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 swing set is not a living thing.
Swing sets 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: Select the mammal below.

Choices:
A. cassowary
B. red howler
C. flamingo
D. box turtle

Mammals have hair or fur and feed their young milk.
Mammals are warm-blooded. Warm-blooded animals can control their body temperature.
A gray wolf 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 box turtle is a reptile. It has scaly, waterproof skin.
Box turtles can live to be over 100 years old!
A red howler is a mammal. It has hair and feeds its young milk.
Howler monkeys have loud calls, or howls. Their calls can be heard over three miles away!
A flamingo is a bird. It has feathers, two wings, and a beak.
Flamingos live in large groups. These groups are called flocks.
A cassowary is a bird. It has feathers, two wings, and a beak.
Cassowaries have wings, but they cannot fly! They can run very fast.

natural science


Question:
What do these two changes have in common?
sawing a log in half
stretching a rubber band

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.
Sawing a log in half is a physical change. The log splits into two pieces. But the pieces are still made of the same type of matter.
Stretching a rubber band is a physical change. The rubber band gets longer. But it is 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 part whose main job is to give strength and stiffness to a plant cell.

Choices:
A. Golgi
B. cytoplasm
C. cell wall
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.

The cell wall is the outer layer of a plant cell. It gives the cell strength and stiffness, which helps the cell keep its shape. The cell wall also supports and protects the cell.

natural science


Question: What is the probability that a rose plant produced by this cross will have dark yellow flowers?

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

In a group of rose plants, some individuals have light yellow flowers and others have dark yellow flowers. In this group, the gene for the flower color trait has two alleles. The allele for light yellow flowers (F) is dominant over the allele for dark yellow flowers (f).
This Punnett square shows a cross between two rose 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.
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: How long is a paintbrush?

Choices:
A. 12 yards
B. 12 miles
C. 12 feet
D. 12 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 paintbrush is 12 inches.
12 feet, 12 yards, and 12 miles are all too long.

natural science


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

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

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.
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 vestigial wings or normal wings, consider whether each phenotype is the dominant or recessive allele's version of the wing type trait. The question tells you that the n allele, which is for vestigial wings, is recessive to the N allele, which is for normal wings.
Vestigial wings is the recessive allele's version of the wing type trait. A fruit fly with the recessive version of the wing type trait must have only recessive alleles for the wing type gene. So, offspring with vestigial wings must have the genotype nn.
There are 2 boxes in the Punnett square with the genotype nn. These boxes are highlighted below.
Normal wings is the dominant allele's version of the wing type trait. A fruit fly with the dominant version of the wing type trait must have at least one dominant allele for the wing type gene. So, offspring with normal wings must have the genotype NN or Nn.
There are 2 boxes in the Punnett square with the genotype NN or Nn. These boxes are highlighted below.
So, the expected ratio of offspring with vestigial wings to offspring with normal wings is 2:2. This means that, on average, this cross will produce 2 offspring with vestigial wings for every 2 offspring with normal wings.

natural science


Question:
What do these two changes have in common?
photosynthesis
a penny tarnishing

Choices:
A. Both are caused by heating.
B. Both are only physical changes.
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.
Photosynthesis is a chemical change. Plants make sugar using carbon dioxide, water, and energy from sunlight.
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.
Neither change is caused by heating.
Both are caused by cooling.
Neither change is caused by cooling.

natural science


Question: Select the vertebrate.

Choices:
A. common ostrich
B. moon jellyfish
C. castor bean tick
D. fireworm

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.

Like other jellyfishes, a moon jellyfish is an invertebrate. It does not have a backbone. It has a soft body.
A castor bean tick is an insect. Like other insects, a castor bean tick is an invertebrate. It does not have a backbone. It has an exoskeleton.
A fireworm is a worm. Like other worms, a fireworm is an invertebrate. It does not have a backbone. It has a soft body.
A common ostrich is a bird. Like other birds, a common ostrich is a vertebrate. It has a backbone.

natural science


Question: Select the invertebrate.

Choices:
A. yak
B. Surinam horned frog
C. peafowl
D. fly

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 yak is a mammal. Like other mammals, a yak is a vertebrate. It has a backbone.
A fly is an insect. Like other insects, a fly is an invertebrate. It does not have a backbone. It has an exoskeleton.
A peafowl is a bird. Like other birds, a peafowl is a vertebrate. It has a backbone.
A Surinam horned frog is an amphibian. Like other amphibians, a Surinam horned frog is a vertebrate. It has a backbone.

natural science


Question: Select the vertebrate.

Choices:
A. earthworm
B. giant octopus
C. robin
D. saturn 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 saturn butterfly is an insect. Like other insects, a saturn butterfly is an invertebrate. It does not have a backbone. It has an exoskeleton.
An earthworm is a worm. Like other worms, an earthworm is an invertebrate. It does not have a backbone. It has a soft body.
Like other octopuses, a giant octopus is an invertebrate. It does not have a backbone. It has a soft body.
A robin is a bird. Like other birds, a robin is a vertebrate. It has a backbone.

natural science


Question:
What do these two changes have in common?
baking cookies
rust forming on a metal gate

Choices:
A. Both are only physical changes.
B. Both are chemical changes.
C. Both are caused by cooling.
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 cookies is a chemical change. Cookies are made from cookie dough. Baking turns the cookie dough into cookies. The cookies are a different type of matter than the dough.
Rust forming on a metal gate is a chemical change. As the gate rusts, the metal turns into a different type of matter called rust. Rust is reddish-brown and falls apart easily.
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 rust forming on a metal gate is not.
Both are caused by cooling.
Neither change is caused by cooling.

natural science