Go to section Pretest 1.True or False: Compounds have fixed compositions. 2.What is an atom? 3.Which of the following units is a unit of mass? a.mL b.˚C c.g d.cm Chapter 4

Go to section Pretest (continued) 4.Volume is a.the straight-line distance between two points. b.the quantity of matter in an object. c.the amount of space taken up by an object. d.a representation of an object or event. 5.What is density? Chapter 4

Go to section Pretest (continued) 6.Which two of the following events can take place when a liquid absorbs energy? a.The average kinetic energy of the particles in the liquid increases. b.The temperature decreases. c.The liquid freezes. d.The liquid changes to a gas. Chapter 4

Go to section Interest Grabber Using Analogies The network of blood vessels in your body is like the network of streets and highways in a large city. How are the two networks similar? Both networks are used to transport objects from one location to another. The comparison is an example of an analogy. An analogy uses a similarity to compare two objects or systems. A familiar object is often used to help explain a less familiar object. 1.Atoms in compounds are like bricks in a wall. Explain this analogy. 2.Think of another analogy for atoms in compounds. Section 4.1

Go to section Reading Strategy Summarizing Section 4.1 a.Daltonb.Indivisible, solid spheres c. Thomsond. Negative charges evenly scattered through a positively charged mass of matter (plum pudding model) e.Deflection of alpha particles passing through gold foil

Go to section Thomson’s Experiments Figure 5

Go to section The Gold Foil Experiment Figure 5

Go to section Interest Grabber The “Rutherford” Atom In Section 4.1 you were told that if the Houston Astrodome were a model for an atom, then a marble could represent its nucleus. 1.Think of another physical analogy for a “Rutherford” atom other than the Astrodome. 2.Identify what represents the atom and what represents the nucleus in your analogy. 3.How good a match is your analogy for an actual atom? In what ways is it misleading? Section 4.2

Go to section Reading Strategy Monitoring Your Understanding Section 4.2 Most students will know that atoms are the "building blocks" of matter, and some may know that atoms contain subatomic particles. Based on the title of the section, students may say that they want to learn more about the structure of atoms.

Go to section A Scientific Method Figure 12

Go to section Interest Grabber Probability Scientists use probability to describe how electrons behave in atoms. Try the following activity to learn more about probability. Tape a large piece of paper to the wall. Draw a circle 1-foot in diameter in the center of the paper. Mark the exact center of the circle. Leave plenty of room on all sides of the circle. Blindfold a partner. Place your partner two arm lengths away from the wall facing the wall. Give your partner a small sticker. Have your partner walk forward and try to place the sticker at the center of the circle. Repeat this process five times. 1.Describe the pattern of the stickers. 2.Was the probability of placing a sticker in the center of the circle high or low? 3.What could increase the probability of placing a sticker inside the circle? Section 4.3

Go to section Reading Strategy a.Electron moves to higher energy level. b.Electron moves to lower energy level. Section 4.3 Sequencing

Go to section Number of Orbitals and Electrons in Energy Levels Figure 15

Pretest Answers 1.True or False: Compounds have fixed compositions. 2.What is an atom? 3.Which of the following units is a unit of mass? a.mL b.˚C c.g d.cm Chapter 4 Click the mouse button to display the answers. An atom is the smallest particle of an element.

Chapter 4 Pretest Answers (continued) Click the mouse button to display the answers. 4.Volume is a.the straight-line distance between two points. b.the quantity of matter in an object. c.the amount of space taken up by an object. d.a representation of an object or event. 5.What is density? Density is the ratio of the mass of a substance to its volume.

Chapter 4 Pretest Answers (continued) Click the mouse button to display the answers. 6.Which two of the following events can take place when a liquid absorbs energy? a.The average kinetic energy of the particles in the liquid increases. b.The temperature decreases. c.The liquid freezes. d.The liquid changes to a gas.

Interest Grabber Answers 1.Atoms in compounds are like bricks in a wall. Explain this analogy. You may say that atoms and bricks are both small units from which larger structures are built. 2.Think of another analogy for atoms in compounds. Answers will vary. Possible analogies include corals in a reef, threads in a woven rug, seats in a stadium, or blades of grass in a lawn. Section 4.1

Interest Grabber Answers 1.Think of another physical analogy for a “Rutherford” atom other than the Astrodome. 2.Identify what represents the atom and what represents the nucleus in your analogy. 1. and 2. Sample answers: a fruit with a seed representing the nucleus; a small object embedded in the center of a transparent glass or plastic sphere; a chocolate-covered cherry or nut; the smallest object in a set of nested objects of increasing size 3.How good a match is your analogy for an actual atom? In what ways is it misleading? The main flaws in most physical analogies are the relative sizes of the “nucleus” and “atom,” and the lack of unfilled space surrounding the nucleus. Section 4.2

Interest Grabber Answers Section Describe the pattern of the stickers. Sample responses: Three stickers were placed inside the circle, one sticker was placed on the center dot. 2.Was the probability of placing a sticker in the center of the circle high or low? Sample response: The probability of placing the sticker in the center was low. 3.What could increase the probability of placing a sticker inside the circle? A larger circle would increase the probability. So would starting the blindfolded person from a location nearer to the wall.

Chapter 4 Go Online Self-grading assessment For links on atomic theory, go to and enter the Web Code as follows: ccn For links on subatomic particles, go to and enter the Web Code as follows: ccn For links on energy levels, go to and enter the Web Code as follows: ccn

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