Description

1. mixture, compound, mixture, element

1. a. compound
2. homogeneous mixture
3. element
4. heterogeneous mixture

1. a. physical property
2. chemical change
3. physical property
4. physical property
5. chemical change
6. chemical change

1. The particles in hot coffee are moving more rapidly than those in cold coffee.

1. This is an endothermic process since heat is absorbed by the system. The liquid water absorbed heat energy to become steam; therefore, the steam has the higher energy.

1. Potential energy is the energy that is stored. The new battery has stored energy and therefore has more potential energy. The dead battery does not have stored energy and is more stable.

1. a. hypothesis
2. law
3. theory

1. When Arthur Barclay suspected that the Pacific yew might have disease-fighting properties, this was only a tentative explanation, which is the same as a hypothesis. Some types of experiments to test this hypothesis included studies on tumor growth and cancer reproduction. Testing in humans, called clinical trials, was also done.

Additional Problems

1.2 Describing Matter

1. Matter is anything that has mass and takes up volume.

1. Air is made of matter. It has a mass and occupies a volume of space.
2. A football is made of matter. It has a mass and occupies a volume of space.
   1. Sunlight is not made of matter. It doesn’t have a mass and doesn’t occupy a volume of space.
   2. Water is made of matter. It has a mass and occupies a volume of space.

1. Matter is anything that has mass and takes up volume.

1. Sweet tea is made of matter. It has a mass and occupies a volume of space.
   1. Happiness is not made of matter. It doesn’t have mass and doesn’t occupy a volume of space.
   2. Sound is not made of matter. It doesn’t have mass and doesn’t occupy a volume of space.
   3. Sand is made of matter. It has a mass and occupies a volume of space.

1. Composition refers to the simple components that make up the material. Structure refers to both the composition and arrangement of those simpler substances.

1. The simplest form of matter is an element. An element is a substance that is made of only one type of atom. Compounds are substances that are composed of more than one element, bound together in fixed ratios.

1. Mixtures in which the components are evenly blended throughout are homogeneous mixtures. In contrast, heterogeneous mixtures contain regions with significantly different composition.

1. Earth’s atmosphere is an example of a homogeneous mixture. The atmosphere is a mixture of various gases in which the components are evenly blended throughout.
2. Fluorine gas is an example of an element, since it’s a substance that contains only fluorine atoms.
3. Carbon monoxide is an example of a compound. Compounds are substances that are composed of more than one element, bound together in fixed ratios.

16.16.

1. An alloy of tin and gold is an example of a homogeneous mixture. The alloy is a mixture of gold and tin in which the components are evenly blended throughout.
2. Phosphorus trichloride is an example of a compound. Compounds are substances that are composed of more than one element, bound together in fixed ratios.
3. Titanium metal is an example of an element. An element is a substance that is made of only one type of atom.

17.17.

1. Element. Only one color of spheres is shown, meaning only one type of atom is present.
2. Heterogeneous mixture. The image contains an element (gray spheres) and a compound (green and white spheres). There are two regions with significantly different compositions.
   1. Homogeneous mixture. The image contains two different-colored spheres representing two different elements. The two components are evenly blended throughout the mixture.

1. Saltwater is best described as a homogeneous mixture. Homogeneous mixtures are mixtures in which the components are evenly blended throughout. The salt particles dissolved in water are evenly distributed throughout the water.

1. Particles in a solid vibrate within their spaces in the ordered framework. As a solid is heated to a liquid, the atoms vibrate faster. The more heat we add, the faster the atoms move, until eventually they begin to break out of the rigid framework and travel freely past each other. The substance is now in the liquid state. The particles in a liquid move randomly, but remain close to each other. If we continue heating the liquid, the atoms move faster and faster, until they begin to break out of the liquid phase and enter the gas phase. Particles in the gas phase move about freely, interacting very little with each other.

1. The image represents a gaseous mixture. The mixture contains two elements and a compound. The particles are moving about freely and interact very little with each other.

21.21.

1. solid
2. gas
3. solid

22.22.

1. liquid
2. gas
3. liquid

23.23.

1. Physical, because we can observe color without changing the identity of the substance.
2. Physical, because measuring the conductivity of the metal doesn’t change the identity of the substance.
3. Chemical, because magnesium metal changes its identity to form a new compound.
4. Chemical, because the egg changes its identity.
5. Physical, because steam is still water. The identity of the water does not change when it changes from a liquid to a gas.

24.24.

1. Physical, because sugar has not been altered in its structure. We can obtain sugar again by the evaporation of water.
2. Chemical, because charcoal changes its identity to form carbon dioxide and ash.
3. Chemical, because the identity of the original molecules within the stomach are now different following digestion.
4. Physical, because the bar’s shape has changed, but its identity has not.

25.25.

1. Physical, because we can observe color without changing the identity of the substance.
   1. Chemical, because Taxol’s chemical structure changes when it is broken down in the liver into simpler compounds.
   2. Physical, because we can observe Taxol’s melting point without changing the identity of the substance.

26.26.

1. Physical, because we can observe aspirin’s melting point without changing the identity of the substance.
2. Chemical, because aspirin’s chemical structure changes when it reacts with sodium hydroxide to make new compounds.
3. Chemical, because aspirin’s chemical structure changes when it reacts in the stomach to make new compounds.

1. Physical change; the solid’s identity didn’t change when going from a solid to a gas.

1. Chemical change, because the identity of nitrogen and hydrogen gas changes to form ammonia, a new compound.

1. Physical change, because the seawater mixture is separated into two pure compounds (salt and water), but the identity of these substances does not change. The separation of mixtures involves physical changes.

1. Chemical change, because the identity of water changes when it is broken down into the elements hydrogen and oxygen.

1.3 Energy and Change

1. When a substance is heated, the particles within the substance vibrate or move faster and faster.

1. Water molecules in ice are held together tightly in a rigid framework. There is some vibration of the water molecules, but overall these molecules are held tightly in place. Water molecules found in liquid water move much more freely and quickly.

33.33.

1. The rock on the top of the hill has more potential energy due to its position. The rock at the bottom of the hill is more stable because it has no more potential energy to release.
2. Wood has more potential energy because it has more stored chemical energy in it than the ashes have. As such, the ashes are more stable because they have no more potential energy to release.
   1. A tightly wound spring has more potential energy because it has stored energy. The relaxed spring is more stable because it has no potential energy to release.

34.34.

1. Steam has more kinetic energy than liquid water, so this event results in a higher- energy product.
2. The explosion produced ash and paper, both of which are not explosive. As such the explosion leads to a lower-energy product.
3. The stored energy in the candle is released to give off heat, light, carbon dioxide, and water. This event leads to lower-energy products because stored energy was released.
4. The woody material that is produced will have stored energy in it that can be released. The process of making woody material from carbon dioxide, water, and sunlight results in a higher-energy product.

35.35.

1. A mixture because it’s composed of two gases, hydrogen and oxygen.
2. A compound because it has a fixed ratio of 2 hydrogen atoms for every oxygen atom.
3. Chemical change because the identities of both gases, hydrogen and oxygen, were changed to make water.
4. Because energy was released (exothermic) the product, water, has less potential energy and is more stable.

1. a. This container is a mixture of substances.
2. This container contains a pure compound.
3. Because a new compound was made, a chemical change occurred.
4. Because energy was released, the arrangement of atoms in the products is more stable than before.

1. Because it absorbs energy from the sun, the growth is endothermic.

38.38.

1. Water is more stable because energy was required to break it down into hydrogen and oxygen, meaning the products have more potential energy than water has.
2. Because energy was added to the water to cause a chemical change to hydrogen and oxygen, this reaction is endothermic.

1.4 The Scientific Method

1. A hypothesis is a tentative explanation that has not been tested, whereas a theory is an idea supported by experimental evidence.

1. A law describes observations that are true in widely varying circumstances. A scientific law does not explain why something occurs; it simply observes that it is true. A theory is

an idea supported by experimental evidence. Scientific laws concisely describe how things behave, while theories explain how or why things happen.

1. To test the hypothesis, you could assess the students several times during the 9–11 a.m. time frame and at other time frames during the day. Then, you would review the results and compare how the students did in each time frame. Did the students do better during the 9–11 a.m. slot or not? If they did, then your hypothesis was proven correct. To increase the reliability of your results, you should test the students several times during each time frame and make sure the assessment is of similar difficulty each time.

1. You could carefully dig up your south end plants and replant them at the north end of the garden. After several days, you can observe any positive or negative changes. If the replants are growing much better than before (at least as well as the north end plants), then your hypothesis is correct.