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the chemical formula for the compound that consists of barium ions (ba+2) and oxide ions (o-2) is | (A) OBa (B) O2Ba2 (C) Ba2O2 (D) BaO | D | Barium (Ba) is one of six elements in group 2 of the periodic table, which is shown in Figure 1.1. Elements in this group are called alkaline Earth metals. These metals are silver or gray in color. They are relatively soft and low in density, although not as soft and lightweight as alkali metals. |
a chemical reaction changes some substances into other substances with different chemical properties. | (A) true (B) false | A | A chemical reaction is a process in which some substances change into different substances. Substances that start a chemical reaction are called reactants. Substances that are produced in the reaction are called products. Reactants and products can be elements or compounds. A chemical reaction can be represented by thi... |
the substances involved in a chemical reaction may be elements or compounds. | (A) true (B) false | A | A chemical reaction is a process in which some substances change into different substances. Substances that start a chemical reaction are called reactants. Substances that are produced in the reaction are called products. Reactants and products can be elements or compounds. A chemical reaction can be represented by thi... |
during a chemical reaction | (A) chemical bonds break (B) matter is destroyed (C) new atoms form (D) two of the above | A | A change in color is just one of several potential signs that a chemical reaction has occurred. Other potential signs include: Change in temperature-Heat is released or absorbed during the reaction. Production of a gas-Gas bubbles are released during the reaction. Production of a solid-A solid settles out of a liquid s... |
which of the following represents a synthesis reaction? | (A) 2H2 + O2 → 2H2O (B) 2K + 2H2O → 2KOH + H2 (C) 2NaCl → 2Na + Cl2 (D) none of the above | A | A synthesis reaction occurs when two or more reactants combine to form a single product. A synthesis reaction can be represented by the general equation: A+B !C In this general equation (and others like it in this lesson), the letters A, B,C, and so on represent atoms or ions of elements. The arrow shows the direction ... |
which type of reaction is represented by the following chemical equation? ch4 + 2o2 co2 + 2h2o | (A) combustion reaction (B) decomposition reaction (C) single replacement reaction (D) double replacement reaction | A | A chemical reaction occurs when some substances change chemically to other substances. Chemical reactions are represented by chemical equations. Consider a simple chemical reaction, the burning of methane. In this reaction, methane (CH4 ) combines with oxygen (O2 ) in the air and produces carbon dioxide (CO2 ) and wate... |
factors that affect the rate of a chemical reaction include | (A) concentration of reactants (B) surface area of reactants (C) temperature of reactants (D) all of the above | D | How fast a chemical reaction occurs is called the reaction rate. Several factors affect the rate of a given chemical reaction. They include the: temperature of reactants. concentration of reactants. surface area of reactants. presence of a catalyst. |
warmer reactants react more quickly than cooler reactants. | (A) true (B) false | A | When the temperature of reactants is higher, the rate of the reaction is faster. At higher temperatures, particles of reactants have more energy, so they move faster. They are more likely to bump into one another and to collide with greater force. For example, when you fry an egg, turning up the heat causes the egg to ... |
food spoils faster at higher temperatures because heat is a catalyst. | (A) true (B) false | B | When the temperature of reactants is higher, the rate of the reaction is faster. At higher temperatures, particles of reactants have more energy, so they move faster. As a result, they are more likely to bump into one another and to collide with greater force. For example, food spoils because of chemical reactions, and... |
which statement is true about any catalyst? | (A) It is a reactant in a chemical reaction (B) It is used up in a chemical reaction (C) It can speed up many chemical reactions (D) all of the above | C | Catalysts interact with reactants so the reaction can occur by an alternate pathway that has a lower activation energy. Activation energy is the energy needed to start a reaction. When activation energy is lower, more reactant particles have enough energy to react so the reaction goes faster. Many catalysts work like t... |
warmer reactants have more energy and move faster. | (A) true (B) false | A | When the temperature of reactants is higher, the rate of the reaction is faster. At higher temperatures, particles of reactants have more energy, so they move faster. They are more likely to bump into one another and to collide with greater force. For example, when you fry an egg, turning up the heat causes the egg to ... |
all compounds consist of a fixed ratio of elements. | (A) true (B) false | A | A compound is a unique substance that forms when two or more elements combine chemically. Compounds form as a result of chemical reactions. The elements in compounds are held together by chemical bonds. A chemical bond is a force of attraction between atoms or ions that share or transfer valence electrons. Click image ... |
covalent compounds are compounds that | (A) consist only of nonmetallic elements (B) have atoms that share electrons (C) exist as individual molecules (D) all of the above | D | Compounds that form from two or more nonmetallic elements, such as carbon and hydrogen, are called covalent compounds. In a covalent compound, atoms of the different elements are held together in molecules by covalent bonds. These are chemical bonds in which atoms share valence electrons. The force of attraction betwee... |
water is an example of a covalent compound. | (A) true (B) false | A | Water (H2 O) is an example of a chemical compound. Water molecules always consist of two atoms of hydrogen and one atom of oxygen. Like water, all other chemical compounds consist of a fixed ratio of elements. It doesnt matter how much or how little of a compound there is. It always has the same composition. |
ionic compounds are compounds that | (A) consist only of metallic elements (B) have atoms that transfer electrons (C) exist as individual ions (D) all of the above | B | Ionic compounds contain ions of metals and nonmetals held together by ionic bonds. Ionic compounds do not form molecules. Instead, many positive and negative ions bond together to form a structure called a crystal. You can see an example of a crystal in Figure 7.5. It shows the ionic compound sodium chloride. Positive ... |
carbon dioxide is an example of an ionic compound. | (A) true (B) false | B | The Table 1.1 shows four examples of compounds and their chemical formulas. The first two compounds are ionic compounds, and the second two are covalent compounds. Each formula shows the ratio of ions or atoms that make up the compound. Name of Compound Type of Compound Sodium chloride ionic Calcium iodide ionic Hydrog... |
a rainbow includes all the colors of visible light. | (A) true (B) false | A | The only light that people can see is called visible light. It refers to a very narrow range of wavelengths in the electromagnetic spectrum that falls between infrared light and ultraviolet light. Within the visible range, we see light of different wavelengths as different colors of light, from red light, which has the... |
visible light includes all the wavelengths of light that the human eye can detect. | (A) true (B) false | A | Visible light is light that has wavelengths that can be detected by the human eye. The wavelength of visible light determines the color that the light appears. As you can see in the Figure 1.1, light with the longest wavelength appears red, and light with the shortest wavelength appears violet. In between are all the o... |
leaves appear green because they | (A) absorb only green light (B) reflect only green light (C) transmit only green light (D) none of the above | B | In plants, most chloroplasts are found in the leaves. Therefore, all the raw materials needed for photosynthesis must be present in the leaves. These materials include light, water, and carbon dioxide. The shape of the leaves gives them a lot of surface area to absorb light for photosynthesis. Roots take up water from ... |
if only blue light strikes green leaves, the leaves appear | (A) green (B) blue (C) black (D) white | C | An opaque object is one that doesnt let light pass through it. Instead, it reflects or absorbs the light that strikes it. Many objects, such as the leaves pictured in the Figure 1.3, reflect just one or a few wavelengths of visible light and absorb the rest. The wavelengths that are reflected determine the color that a... |
primary colors of light include | (A) red (B) cyan (C) magenta (D) all of the above | A | The human eye can distinguish only red, green, and blue light. These three colors are called the primary colors of light. All other colors of light can be created by combining the primary colors. Look at the Venn diagram 1.5. Red and green light combine to form yellow light. Red and blue light combine to form magenta l... |
primary colors of pigments include | (A) yellow (B) blue (C) green (D) none of the above | A | Many objects have color because they contain pigments. A pigment is a substance that colors materials by reflecting light of certain wavelengths and absorbing light of other wavelengths. A very common pigment is the dark green pigment called chlorophyll, which is found in plants. Chlorophyll absorbs all but green wavel... |
the net force acting on you when you sit still in a chair is zero. | (A) true (B) false | A | When two forces act on an object in opposite directions, like the book on the table, the net force is equal to the difference between the two forces. In other words, one force is subtracted from the other to calculate the net force. If the opposing forces are equal in strength, the net force is zero. Thats what happens... |
when two forces act on an object in opposite directions, you calculate the net force by | (A) dividing the two forces (B) subtracting the two forces (C) finding the average of the two forces (D) none of the above | B | When two forces act on an object in opposite directions, like the book on the table, the net force is equal to the difference between the two forces. In other words, one force is subtracted from the other to calculate the net force. If the opposing forces are equal in strength, the net force is zero. Thats what happens... |
when two forces act on an object in the same direction, you calculate the net force by | (A) adding the two forces (B) multiplying the two forces (C) finding the larger of the two forces (D) none of the above | A | Two forces may act on an object in the same direction. You can see an example of this in Figure 13.5. After the man on the left lifts up the couch, he will push the couch to the right with a force of 25 newtons. At the same time, the man to the right is pulling the couch to the right with a force of 20 newtons. When tw... |
when two forces act on the same object in opposite directions, the net force is always greater than the individual forces. | (A) true (B) false | B | When two forces act on an object in opposite directions, like the book on the table, the net force is equal to the difference between the two forces. In other words, one force is subtracted from the other to calculate the net force. If the opposing forces are equal in strength, the net force is zero. Thats what happens... |
when two forces act on the same object in the same direction, the net force is always less than the individual forces. | (A) true (B) false | B | When two forces act on an object in opposite directions, like the book on the table, the net force is equal to the difference between the two forces. In other words, one force is subtracted from the other to calculate the net force. If the opposing forces are equal in strength, the net force is zero. Thats what happens... |
most fuels in combustion reactions are compounds called | (A) proteins (B) ionic compounds (C) hydrocarbons (D) halogens | C | The fuel that burns in a combustion reaction is often a substance called a hydrocarbon. A hydrocarbon is a compound that contains only carbon (C) and hydrogen (H). Fossil fuels, such as natural gas, consist of hydrocarbons. Natural gas is a fuel that is commonly used in home furnaces and gas stoves (see Figure 8.11). T... |
the main component of natural gas is nitrogen. | (A) true (B) false | B | Natural gas is mostly methane. |
products of incomplete combustion include only carbon dioxide and water. | (A) true (B) false | B | A combustion reaction occurs when a substance reacts quickly with oxygen (O2 ). For example, in the Figure usually referred to as fuel. The products of a complete combustion reaction include carbon dioxide (CO2 ) and water vapor (H2 O). The reaction typically gives off heat and light as well. The general equation for a... |
some compound machines consist of thousands of simple machines. | (A) true (B) false | A | A compound machine is a machine that consists of more than one simple machine. Some compound machines consist of just two simple machines. You can read below about two examplesthe wheelbarrow and corkscrew. Other compound machines, such as bicycles, consist of many simple machines. Big compound machines such as cars ma... |
when you use a wheelbarrow, you apply effort to the | (A) wheel (B) axle (C) lever (D) two of the above | D | Look at the wheelbarrow in the Figure 1.1. It is used to carry heavy objects. It consists of two simple machines: a lever and a wheel and axle. Effort is applied to the lever by picking up the handles of the wheelbarrow. The lever, in turn, applies upward force to the load. The force is increased by the lever, making t... |
a corkscrew consists of | (A) two levers (B) a screw (C) a wheel and axle (D) two of the above | D | The corkscrew in the Figure 1.2 is also a compound machine. It is used to pierce a cork and pull it out of the neck of a bottle. It consists of a screw and two levers. Turning the handle on top twists the screw down into the center of the cork. Then, pushing down on the two levers causes the screw to pull upward, bring... |
all machines must overcome friction. | (A) true (B) false | A | Friction is a force that opposes motion between any surfaces that are touching. All machines have moving parts and friction, so they have to use some of the work that is applied to them to overcome friction. This makes all machines less than 100 percent efficient. Because compound machines have more moving parts than s... |
no machine is 100 percent efficient. | (A) true (B) false | A | You read above that machines do not increase the work done on an object. In other words, you cant get more work out of a machine than you put into it. In fact, machines always do less work on the object than the user does on the machine. Thats because all machines must use some of the work put into them to overcome fri... |
which of the following is a compound? | (A) air (B) oxygen (C) carbon dioxide (D) two of the above | C | There are millions of different substances in the world. Thats because elements can combine in many different ways to form new substances. In fact, most elements are found in compounds. A compound is a unique substance that forms when two or more elements combine chemically. An example is water, which forms when hydrog... |
a compound always has the same elements in the same proportions. | (A) true (B) false | A | There are millions of different substances in the world. Thats because elements can combine in many different ways to form new substances. In fact, most elements are found in compounds. A compound is a unique substance that forms when two or more elements combine chemically. An example is water, which forms when hydrog... |
the properties of compounds are the same as the properties of the elements that form them. | (A) true (B) false | B | A compound is a unique substance that forms when two or more elements combine chemically. For example, the compound carbon dioxide forms when one atom of carbon (grey in the model above) combines with two atoms of oxygen (red in the model). Another example of a compound is water. It forms when two hydrogen atoms combin... |
which of the following substances is a compound that forms ionic crystals? | (A) water (B) sodium chloride (C) carbon dioxide (D) none of the above | B | Many compounds form molecules, but ionic compounds form crystals instead. A crystal consists of many alternating positive and negative ions bonded together in a matrix. Look at the crystal of sodium chloride (NaCl) in the Figure bonds. Sodium chloride crystals are cubic in shape. Other ionic compounds may have crystals... |
which of the following gases is a compound that forms molecules? | (A) air (B) carbon dioxide (C) oxygen (D) nitrogen | B | A molecule is any combination of two or more atoms. The oxygen in the air we breathe is two oxygen atoms connected by a chemical bond to form O2 , or molecular oxygen. A carbon dioxide molecule is a combination of one carbon atom and two oxygen atoms, CO2 . Because carbon dioxide includes two different elements, it is ... |
a molecule consists of two or more atoms bonded together. | (A) true (B) false | A | A molecule is any combination of two or more atoms. The oxygen in the air we breathe is two oxygen atoms connected by a chemical bond to form O2 , or molecular oxygen. A carbon dioxide molecule is a combination of one carbon atom and two oxygen atoms, CO2 . Because carbon dioxide includes two different elements, it is ... |
which statement about energy and chemical reactions is true? | (A) All chemical reactions involve energy (B) Breaking bonds in reactants requires energy (C) Forming bonds in products releases energy (D) all of the above | D | Whether a chemical reaction absorbs or releases energy, there is no overall change in the amount of energy during the reaction. Thats because energy cannot be created or destroyed. This is the law of conservation of energy. Energy may change form during a chemical reactionfor example, from chemical energy to heat energ... |
energy cannot be created or destroyed in chemical reactions. | (A) true (B) false | A | Energy changes form when something happens. But the total amount of energy always stays the same. The Law of Conservation of Energy says that energy cannot be created or destroyed. Scientists observed that energy could change from one form to another. They also observed that the overall amount of energy did not change.... |
energy cannot change form during chemical reactions. | (A) true (B) false | B | Energy changes form when something happens. But the total amount of energy always stays the same. The Law of Conservation of Energy says that energy cannot be created or destroyed. Scientists observed that energy could change from one form to another. They also observed that the overall amount of energy did not change.... |
in an endothermic reaction, products have less chemical energy than reactants. | (A) true (B) false | B | All chemical reactions involve energy. Energy is used to break bonds in reactants, and energy is released when new bonds form in products. In some chemical reactions, called endothermic reactions, less energy is released when new bonds form in the products than is needed to break bonds in the reactants. The opposite is... |
when natural gas burns in a furnace | (A) energy is released in the form of heat and light (B) it takes more energy to break bonds in reactants than to form bonds in products (C) the natural gas creates energy as it burns (D) two of the above | A | The fuel that burns in a combustion reaction contains compounds called hydrocarbons. Hydrocarbons are compounds that contain only carbon (C) and hydrogen (H). The charcoal pictured in the Figure 1.1 consists of hydrocarbons. So do fossil fuels such as natural gas. Natural gas is a fuel that is commonly used in home fur... |
the letter e in einsteins equation e = mc2 stands for | (A) electricity (B) electrons (C) energy (D) efficiency | C | Einsteins equation is possibly the best-known equation of all time. Theres reason for that. The equation is incredibly important. It changed how scientists view energy and matter, which are two of the most basic concepts in all of science. The equation shows that energy and matter are two forms of the same thing. This ... |
the letter c in the equation in question 1 represents a constant. | (A) true (B) false | A | In Einsteins equation, the variable E stands for energy and the variable m stands for mass. The c in the equation is a constant. It stands for the speed of light. The speed of light is 300,000 kilometers (186,000 miles) per second, so c2 is a very big number, no matter what units are used to measure it. Einsteins equat... |
the speed of light is 300,000 km per hour. | (A) true (B) false | B | In space, light travels at about 300,000,000 meters per second (670,000,000 miles per hour). How fast is that? A beam of light could travel from New York to Los Angeles and back again nearly 40 times in just one second. Even at that amazing rate, objects in space are so far away that it takes a lot of time for their li... |
einsteins equation has recently been disproven by real-world evidence. | (A) true (B) false | B | After Einstein proposed his theory, evidence was discovered to support it. For example, scientists shone laser light through two slits in a barrier made of a material that blocked light. You can see the setup of this type of experiment in the Figure 1.2. Using a special camera that was very sensitive to light, they too... |
the amount of energy in a tiny amount of mass is very large. | (A) true (B) false | A | Nuclear energy is produced by splitting the nucleus of an atom. This releases a huge amount of energy. |
einsteins equation shows that mass and energy are not conserved in nuclear reactions. | (A) true (B) false | B | Einsteins equation helps scientists understand what happens in nuclear reactions and why they produce so much energy. When the nucleus of a radioisotope undergoes fission or fusion in a nuclear reaction, it loses a tiny amount of mass. What happens to the lost mass? It isnt really lost at all. It is converted to energy... |
chemical reactions are represented by chemical formulas. | (A) true (B) false | B | A chemical equation is a symbolic representation of a chemical reaction. It is a shorthand way of showing how atoms are rearranged in the reaction. The general form of a chemical equation was introduced in this chapters lesson "Introduction to Chemical Reactions." It is: Reactants ! Products Consider the simple example... |
which choice correctly represents the reaction in which methane burns? | (A) CH4 + 2O2 → CO2 + 2H2O (B) 2CH4 + 2O2 → CO2 + 2H2O (C) CH4 + O2 → CO2 + H2O (D) none of the above | A | A chemical reaction occurs when some substances change chemically to other substances. Chemical reactions are represented by chemical equations. Consider a simple chemical reaction, the burning of methane. In this reaction, methane (CH4 ) combines with oxygen (O2 ) in the air and produces carbon dioxide (CO2 ) and wate... |
the equation h2 + o2 h2o is balanced. | (A) true (B) false | B | Some chemical equations are more challenging to write. Consider the reaction in which hydrogen (H2 ) and oxygen (O2 ) combine to form water (H2 O). Hydrogen and oxygen are the reactants, and water is the product. To write a chemical equation for this reaction, you would start by writing symbols for the reactants and pr... |
which equation shows that mass is conserved in the chemical reaction? | (A) 2Al + 2O2 → 2Al2O3 (B) 2Al + O2 → Al2O3 (C) 4Al + 3O2 → 2Al2O3 (D) none of the above | C | All chemical equations, like equations in math, must balance. This means that there must be the same number of each type of atom on both sides of the arrow. Thats because matter is always conserved in a chemical reaction. This is the law of conservation of mass. Look at the equation above for the reaction between carbo... |
heat is the transfer of thermal energy. | (A) true (B) false | A | Heat is the transfer of thermal energy between substances. Thermal energy is the kinetic energy of moving particles of matter, measured by their temperature. Thermal energy always moves from matter with greater thermal energy to matter with less thermal energy, so it moves from warmer to cooler substances. You can see ... |
when particles of matter in one part of a fluid gain thermal energy they | (A) move more quickly (B) have more collisions (C) spread farther apart (D) all of the above | D | The Figure 1.1 shows how convection occurs, using hot water in a pot as an example. When particles in one area of a fluid (in this case, the water at the bottom of the pot) gain thermal energy, they move more quickly, have more collisions, and spread farther apart. This decreases the density of the particles, so they r... |
when particles are more spread out, they have higher density. | (A) true (B) false | B | Density is mass per unit volume. Density is a measure of how closely molecules are packed together. The closer together they are, the greater the density. Since air is a gas, the molecules can pack tightly or spread out. The density of air varies from place to place. Air density depends on several factors. One is tempe... |
higher density particles sink downward through a fluid. | (A) true (B) false | A | Two factors influence the pressure of fluids. They are the depth of the fluid and its density. A fluid exerts more pressure at greater depths. Deeper in a fluid, all of the fluid above it results in more weight pressing down. This causes greater pressure the deeper you go. Denser fluids such as water exert more pressur... |
convection currents transfer thermal energy through earths | (A) oceans (B) atmosphere (C) molten rock (D) all of the above | D | Convection currents transfer thermal energy through many fluids, not just hot water in a pot. For example, convection currents transfer thermal energy through molten rock below Earths surface, through water in the oceans, and through air in the atmosphere. Convection currents in the atmosphere create winds. You can see... |
work as defined in physics always involves | (A) force (B) motion (C) energy (D) all of the above | D | Work is defined differently in physics than in everyday language. In physics, work means the use of force to move an object. The teens who are playing basketball in the picture above are using force to move their bodies and the basketball, so they are doing work. The teen who is studying isnt moving anything, so she is... |
most cooling systems get energy from electricity. | (A) true (B) false | A | A refrigerator is an example of a cooling system. Another example is an air conditioner. The purpose of any cooling system is to transfer thermal energy in order to keep things cool. A refrigerator, for example, transfers thermal energy from the cool air inside the refrigerator to the warm air in the kitchen. If youve ... |
in a cooling system, the refrigerant | (A) has a high boiling point (B) absorbs thermal energy from air inside the refrigerator (C) pumps cool air into the refrigerator (D) two of the above | B | The key to how a refrigerator or other cooling system works is the refrigerant. A refrigerant is a substance such as FreonTM that has a low boiling point and changes between liquid and gaseous states as it passes through the refrigerator. As a liquid, the refrigerant absorbs thermal energy from the cool air inside the ... |
the refrigerant changes between solid and liquid states as it passes through the refrigerator. | (A) true (B) false | B | The key to how a refrigerator or other cooling system works is the refrigerant. A refrigerant is a substance such as FreonTM that has a low boiling point and changes between liquid and gaseous states as it passes through the refrigerator. As a liquid, the refrigerant absorbs thermal energy from the cool air inside the ... |
as a liquid the refrigerant transfers thermal energy to the outside air. | (A) true (B) false | B | The key to how a refrigerator or other cooling system works is the refrigerant. A refrigerant is a substance such as FreonTM that has a low boiling point and changes between liquid and gaseous states as it passes through the refrigerator. As a liquid, the refrigerant absorbs thermal energy from the cool air inside the ... |
in covalent bonds, the atoms that form bonds | (A) may be metals or nonmetals (B) transfer electrons (C) may both be the same element (D) all of the above | C | A covalent bond is the force of attraction that holds together two atoms that share a pair of valence electrons. The shared electrons are attracted to the nuclei of both atoms. This forms a molecule consisting of two or more atoms. Covalent bonds form only between atoms of nonmetals. |
electrons in covalent bonds are attracted to the nucleus of just one atom. | (A) true (B) false | B | A covalent bond is the force of attraction that holds together two atoms that share a pair of valence electrons. The shared electrons are attracted to the nuclei of both atoms. This forms a molecule consisting of two or more atoms. Covalent bonds form only between atoms of nonmetals. |
a covalent bond always includes a pair of electrons. | (A) true (B) false | A | A covalent bond is the force of attraction that holds together two atoms that share a pair of valence electrons. The shared electrons are attracted to the nuclei of both atoms. This forms a molecule consisting of two or more atoms. Covalent bonds form only between atoms of nonmetals. |
elements that form diatomic molecules include | (A) oxygen (B) hydrogen (C) chlorine (D) all of the above | D | Covalent bonds between atoms of different elements form covalent compounds. The smallest, simplest covalent compounds have molecules with just two atoms. An example is hydrogen chloride (HCl). It consists of one hydrogen atom and one chlorine atom. The largest, most complex covalent molecules have thousands of atoms. E... |
the formation of one or more covalent bonds always results in a covalent compound. | (A) true (B) false | B | Compounds that form from two or more nonmetallic elements, such as carbon and hydrogen, are called covalent compounds. In a covalent compound, atoms of the different elements are held together in molecules by covalent bonds. These are chemical bonds in which atoms share valence electrons. The force of attraction betwee... |
which of the following is a covalent compound? | (A) H2O (B) NaCl (C) O2 (D) two of the above | A | Compounds that form from two or more nonmetallic elements, such as carbon and hydrogen, are called covalent compounds. In a covalent compound, atoms of the different elements are held together in molecules by covalent bonds. These are chemical bonds in which atoms share valence electrons. The force of attraction betwee... |
forms of crystalline carbon include | (A) coal (B) graphite (C) charcoal (D) two of the above | B | Graphite is one of three forms of crystalline, or crystal-forming, carbon. Carbon also exists in an amorphous, or shapeless, form in substances such as coal and charcoal. Different forms of the same element are called allotropes. Besides graphite, the other allotropes of crystalline carbon are diamond and fullerenes. A... |
the form of carbon in question 6 has been found in meteorites. | (A) true (B) false | A | Scientists study meteorites to learn about Earths interior. Meteorites formed in the early solar system. These objects represent early solar system materials. Some meteorites are made of iron and nickel. They are thought to be very similar to Earths core (Figure 6.2). An iron meteorite is the closest thing to a sample ... |
diamonds are used for | (A) lubricants (B) jewelry (C) blades (D) two of the above | D | Diamonds have many valuable properties. Diamonds are extremely hard and are used for industrial purposes. The most valuable diamonds are large, well-shaped and sparkly. Turquoise is another mineral that is used in jewelry because of its striking greenish-blue color. Many minerals have interesting appearances. Specific ... |
the form of crystalline carbon in which each carbon atom is covalently bonded to three other carbon atoms is | (A) diamond (B) graphite (C) charcoal (D) coal | B | Graphite is one of three forms of crystalline, or crystal-forming, carbon. Carbon also exists in an amorphous, or shapeless, form in substances such as coal and charcoal. Different forms of the same element are called allotropes. Besides graphite, the other allotropes of crystalline carbon are diamond and fullerenes. A... |
fullerenes are used to make soccer balls. | (A) true (B) false | B | A fullerene (also called a Bucky ball) is a form of carbon in which carbon atoms are arranged in a hollow sphere resembling a soccer ball (see Figure 1.4). Each sphere contains 60 carbon atoms, and each carbon atom is bonded to three others by single covalent bonds. The bonds are relatively weak, so fullerenes can diss... |
scientists now reject most of daltons atomic theory. | (A) true (B) false | B | A number of theories in science were first proposed many decades or even centuries ago, but they have withstood the test of time. An example of a physical science theory that has mainly withstood the test of time is Daltons atomic theory. John Dalton was a British chemist who lived in the late 1700s and early 1800s. Ar... |
dalton based his ideas about atoms on his own scientific research. | (A) true (B) false | A | Around 1800, a British chemist named John Dalton revived Democrituss early ideas about the atom. Dalton is pictured in Figure 5.8. He made a living by teaching and just did research in his spare time. Nonetheless, from his research results, he developed one of the most important theories in science. |
dalton investigated | (A) pressure of gases (B) ratios of elements in compounds (C) protons and other subatomic particles (D) two of the above | D | Dalton did many experiments that provided evidence for atoms. For example, he studied the pressure of gases. He concluded that gases must consist of tiny particles in constant motion. Dalton also researched the properties of compounds. He showed that a compound always consists of the same elements in the same ratio. On... |
according to daltons atomic theory | (A) only compounds are made of atoms (B) no two atoms are exactly alike (C) atoms cannot be created or destroyed (D) all of the above | C | From his research, Dalton developed a theory about atoms. Daltons atomic theory consists of three basic ideas: All substances are made of atoms. Atoms are the smallest particles of matter. They cannot be divided into smaller particles, created, or destroyed. All atoms of the same element are alike and have the same mas... |
dalton thought that atoms consist of smaller particles of matter. | (A) true (B) false | B | Dalton incorrectly thought that atoms are tiny solid particles of matter. He used solid wooden balls to model them. The sketch in the Figure 5.9 shows how Daltons model atoms looked. He made holes in the balls so they could be joined together with hooks. In this way, the balls could be used to model compounds. When lat... |
daltons atomic theory was quickly accepted by most other scientists. | (A) true (B) false | A | From his research, Dalton developed a theory about atoms. Daltons atomic theory consists of three basic ideas: All substances are made of atoms. Atoms are the smallest particles of matter. They cannot be divided into smaller particles, created, or destroyed. All atoms of the same element are alike and have the same mas... |
dalton thought that a given compound always consists of the same kinds of atoms in the same proportions. | (A) true (B) false | A | The atomic theory Dalton developed consists of three ideas: All substances are made of atoms. Atoms are the smallest particles of matter. They cannot be divided into smaller particles. They also cannot be created or destroyed. All atoms of the same element are alike and have the same mass. Atoms of different elements a... |
there is a low level of natural radiation in the environment. | (A) true (B) false | A | A low level of radiation occurs naturally in the environment. This is called background radiation. One source of background radiation is rocks, which may contain small amounts of radioactive elements such as uranium. Another source is cosmic rays. These are charged particles that arrive on Earth from outer space. Backg... |
sources of background radiation include | (A) cosmic rays from space (B) atomic bomb testing (C) nuclear power plants (D) all of the above | A | A low level of radiation occurs naturally in the environment. This is called background radiation. One source of background radiation is rocks, which may contain small amounts of radioactive elements such as uranium. Another source is cosmic rays. These are charged particles that arrive on Earth from outer space. Backg... |
background radiation is generally considered harmful to living things. | (A) true (B) false | B | A low level of radiation occurs naturally in the environment. This is called background radiation. It comes from various sources. One source is rocks, which may contain small amounts of radioactive elements such as uranium. Another source is cosmic rays. These are charged particles that arrive on Earth from outer space... |
radiation can cause damage by | (A) knocking electrons out of atoms (B) changing atoms to ions (C) breaking bonds in DNA (D) all of the above | D | You may have seen a sign like the one in Figure 11.3. It warns people that there is radiation in the area. Exposure to radiation can be very dangerous. Radiation damages living things by knocking electrons out of atoms and changing them to ions. Radiation also breaks bonds in DNA and other biochemical compounds. A sing... |
only living things can be harmed by radiation. | (A) true (B) false | B | You may have seen a sign like the one in Figure 11.3. It warns people that there is radiation in the area. Exposure to radiation can be very dangerous. Radiation damages living things by knocking electrons out of atoms and changing them to ions. Radiation also breaks bonds in DNA and other biochemical compounds. A sing... |
which general equation represents a decomposition reaction? | (A) A + B → AB (B) AB → A + B (C) AB + C → AC + B (D) AC → A + B | B | A decomposition reaction occurs when one reactant breaks down into two or more products. It can be represented by the general equation: AB A + B In this equation, AB represents the reactant that begins the reaction, and A and B represent the products of the reaction. The arrow shows the direction in which the reaction... |
products of decomposition reactions are always individual elements. | (A) true (B) false | B | A decomposition reaction is the reverse of a synthesis reaction. In a decomposition reaction, one reactant breaks down into two or more products. This can be represented by the general equation: AB ! A + B Two examples of decomposition reactions are described below. You can see other examples at this URL: http://w |
examples of decomposition reactions include | (A) 2H2O2 → 2H2O + O2 (B) NH3 + H2O → NH4OH (C) 2NaCl → 2Na + Cl2 (D) two of the above | D | A decomposition reaction is the reverse of a synthesis reaction. In a decomposition reaction, one reactant breaks down into two or more products. This can be represented by the general equation: AB ! A + B Two examples of decomposition reactions are described below. You can see other examples at this URL: http://w |
the reaction 2al2o3 4al + 3o2 is a decomposition reaction. | (A) true (B) false | A | A decomposition reaction occurs when one reactant breaks down into two or more products. It can be represented by the general equation: AB A + B In this equation, AB represents the reactant that begins the reaction, and A and B represent the products of the reaction. The arrow shows the direction in which the reaction... |
according to democritus, atoms are | (A) too small to see (B) indestructible (C) unable to be subdivided (D) all of the above | D | Democritus idea of the atom has been called the best guess in antiquity. Thats because it was correct in many ways, yet it was based on pure speculation. It really was just a guess. Heres what Democritus thought about the atom: How many times could you cut this piece of cheese in half? How small would the smallest piec... |
democritus thought that atoms are motionless. | (A) true (B) false | B | Did you ever notice dust motes moving in still air where a beam of sunlight passes through it? You can see an example in the forest scene in the Figure 1.2. This sort of observation gave Democritus the idea that atoms are in constant, random motion. If this were true, Democritus thought, then atoms must always be bumpi... |
democritus thought that atoms are separated from each other by empty space. | (A) true (B) false | A | Democritus thought that different kinds of matter vary because of the size, shape, and arrangement of their atoms. For example, he suggested that sweet substances are made of smooth atoms and bitter substances are made of sharp atoms. He speculated that atoms of liquids are slippery, which allows them to slide over eac... |
what happened to democritus ideas about atoms? | (A) They were ridiculed by Aristotle (B) They were widely accepted in his own lifetime (C) They were almost forgotten for more than 2000 years (D) two of the above | D | Democritus was an important philosopher, but he was less influential than another Greek philosopher named Aristo- tle, who lived about 100 years after Democritus. Aristotle rejected Democritus idea of the atom. In fact, Aristotle thought the idea was ridiculous. Unfortunately, Aristotles opinion was accepted for more t... |
democritus ideas were based on experimental evidence. | (A) true (B) false | B | Democritus was an important philosopher, but he was less influential than another Greek philosopher named Aristo- tle, who lived about 100 years after Democritus. Aristotle rejected Democritus idea of the atom. In fact, Aristotle thought the idea was ridiculous. Unfortunately, Aristotles opinion was accepted for more t... |
the central tendency of a sample can be represented by the | (A) mean (B) median (C) mode (D) any of the above | D | The central tendency of a sample can be represented by the mean, median, or mode. The mean is the average value. It is calculated by adding the individual measurements and dividing the sum by the total number of measurements. The median is the middle value. To find the median, rank all the measurements from smallest to... |
the mean and median of the same set of values are always the same. | (A) true (B) false | B | The central tendency of a sample can be represented by the mean, median, or mode. The mean is the average value. It is calculated by adding the individual measurements and dividing the sum by the total number of measurements. The median is the middle value. To find the median, rank all the measurements from smallest to... |
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