1. Is science a collection of facts or an evolving set of theories? Explain.

2. How do you define a good model?

3. Does the following argument establish the truthfulness of the conclusion? Explain.

• P1 If an object floats on top of a liquid, then the object is less dense than the liquid.
• P2 Oranges float in water.
• C Orange peels are less dense than water.

4. (a) A metal ball was found to "weigh" 4.5 g and displace 1.5 mL of water. What is the density of the metal ball? (b) Another ball also weighed 4.5 g, but has a density of 2.0 g/mL. What is the volume of the second ball? (c) A third ball has a density of 2.0 g/mL and a volume of 0.5 mL. What is the mass of the third ball?

5. The density of an object was experimentally determined five times. The results were 1.8, 2.1, 1.99, 2.24, and 2.2 g/mL. What would you report as the density of the object?

6. Is ice (solid water) more dense or less dense than liquid water? Write a conditional argument to justify your answer.

1. What is the difference between a chemical change and a physical change? Give an example of each.

2. Does the following argument establish the truthfulness of the conclusion? Explain.

• P1 If characteristic colors of light are emitted from atoms as the electrons fall back to lower orbits after being excited, then electrons orbit around the nucleus like planets orbit around the sun.
• P2 Characteristic colors of light are emitted from atoms as the electrons fall back to lower orbits after being excited.
• C Electrons orbit around the nucleus like planets orbit around the sun.

3. Describe the raisin pudding model and explain why was it discarded.

4. How is the position of an electron described in the current model of the atom?

5. Visit our class homepage. View "Gold Foil Experiment" and "Energy Levels" found under "Assignments" and "Homework Set #2". Read the first page of the Energy Level module, but specifically look at the "Multimedia" section. Write a paragraph that explains why viewing these web pages was or wasn’t useful.

6. Someone tells you that an atom has ten electrons. Can you identify the element? Explain.

7. Which elements would you predict to be the most similar: (a) Li and K or (b) Ca and O? Write a conditional argument to support your choice.

8. Explain how a line spectrum is produced.

9. When barium is placed in a flame, a green color appears. Explain why the green color is emitted from the barium.

1. Will a pith ball be attracted to any charged rod (positive or negative)? Explain.

2. When a charged rod is placed next to the top of an electroscope (without touching), the leaves at the bottom of the electroscope separate. When the rod is removed the leaves fall back down to their original position. Explain these observations.

3. When a charged rod is touched to the top of an electroscope, the leaves at the bottom of the electroscope separate. When the rod is removed the leaves remain separated. Explain these observations.

4. When a person holds on to a device that generates a charge, it is observed that their hair "stands on end", each hair getting as far away from other hairs as possible. Explain this observation.

5. What are the three premises that must be used when trying to explain charge interactions?

6. How are charges produced?

7. Write a sound conditional argument with the following conclusion: The ring floats above the rod.

1. What is an ionic compound? What happens, in terms of electrons, when ionic compounds are formed? Why do the atoms in ionic compounds stay together?

2. What would the formulas be for the compounds that are formed between: (a) Ca and Br, (b) Na and O, (c) K and F? Give formulas for seven other ionic compounds (salts).

3. What is the pH of a solution that has an H⁺ concentration of 10^-4? Is it acidic or basic? Explain.

4. Given that HCl turns a solution of water and bromthymol blue (an acid-base indicator) the color yellow and that NaOH turns a solution of water and bromthymol blue the color blue, what can you say about NaHCO₃ which turns a solution of water and bromthymol blue the color blue? Is NaHCO₃ an acid or a base? Defend your choice of acid or base. Be sure to identify all assumptions.

5. Fill in the following table:

6. Fill in the column labeled "Acid/Base/Neutral" for each substance in the table below:

Item	pH	Acid/Base/Neutral
Milk of Magnesia	10
Baking Soda	8.5
Milk	6.8
Black Coffee	5
Banana	4.6
Tomatoes	4.2
Vinegar	3
Lemon Juice	2

7. Does pure water conduct electricity? Explain.

8. View "Making Compounds" under "Content Help" on our class webpage. There are four sections there. Look at each section's "Text" and "Multimedia" (that is four Text and four Multimedia). Write a short evaluation of each.

1. Why do the atoms (hydrogen and oxygen) stay together within the water molecule, H₂O?

2. What is a polar molecule? Give an example and label the "polarity" in a simple model that shows the atoms in the molecule.

3. Identify each of the following as ionic, polar, or nonpolar: (a) KCl, (b) MgO, (c) CO, (d) H₂S, (e) Br₂.

4. Describe and explain what happens when a charged rod is placed near a small stream of (a) water and (b) Wesson oil.

5. Why does water and oil separate after vigorous shaking?

6. Explain how different materials, under the same conditions, could have different boiling points, even if they are about the same molecular weight.

7. Two materials have the same polarity, but one evaporates faster than the other. Explain.

8. Why is Crisco a solid and Wesson Oil a liquid at room temperature?

9. View "More Detail" under "Making Molecules" under "Content Help" on our class webpage. There are five sections there. Look at each section's "Text" and "Multimedia" (that is five Text and five Multimedia). Write a short evaluation of each.

1. An atom has 18 electrons and a +2 charge. (a) What element is it? (b) What is the symbol for the ion of this element? (b) Give the formulas for three salts that could be formed using this element.

2. After combing your hair you observe a piece of lint being attracted to the comb. When the lint touches the comb, it immediately flies away. Explain these two observations.

3. Fluorine, F₂, has about twice the mass of water, H₂O. Fluorine is a gas at room temperature while water is a liquid. Explain completely.

4. A positive charge is brought near the metal ball of an electroscope, but doesn't touch it. Describe what happens to the leaves of the electroscope and explain why it happens.

5. Which has a greater surface tension, oil or water? Explain.

6. What difference, if any, is there in the bonding of atoms within ionic, polar, and nonpolar substances? This question is about the bonding of atoms within the molecules or compounds, not the intermolecular forces between the molecules.

7. Is it possible, according to the current atomic theory, to determine the exact position of an electron? Explain.

8. Does the following argument lead to the truthfulness of the conclusion? Explain completely.

• P1 If hydrochloric acid is placed in water, then the number of OH^- ions in the solution will increase.
• P2 Hydrochloric acid is placed in water.
• C The number of OH^- ions in the solution will increase.

9. When glycerin, which is more dense than water, is slowly added to water, it sinks to the bottom as expected. After vigorous shaking the two liquids mix. Will they separate after standing for some period of time? Explain.

10. When short wavelength ultraviolet light is directed toward a metal leaf that looks silver under regular light nothing happens. When long wavelength ultraviolet light is directed toward the same leaf it appears green. Explain.

11. (a) An object has a mass of 2.5 g and a volume of 5.0 mL, what is the density? (b) A different object has a density of 3.6 g/mL and a mass of 7.2 g, what is the volume?

12. Use the results of Rutherford's gold foil experiment to write a sound conditional argument with the conclusion that the atom has a dense nucleus.

13. What are the formulas for the compounds that are formed between: (a) Ba and I, (b) Li and O, (c) Rb and F, (d) Ca and O, (e) Mg and OH^-?

14. A lake was tested and found to have a pH of 4.3. What do you predict will be produced when (a) An acid is thrown into the lake? (b) A base is thrown into the lake? Explain.

15. Explain what will happen at the molecular level when a rod with a positive charge is placed near a small stream of water that is falling from the tap.

16. Consider the experiment with the balloon and Rice Krispies done in class. Write a conditional argument with the following conclusion: The Rice Krispie is attracted to the balloon.

17. In the paper chromatography experiment we saw that black ink is made from a combination of different colors. (a) Why did some of the ink spots move in water, but not in alcohol? (b) Explain why a separation of colors was observed by some of the inks in water.

18. Determine which liquid, A or B, will evaporate faster in each of the situations given below. If it can't be determined put "not conclusive."

19. Explain why the boiling point goes up or down in each of the following cases. (a) H₂O (100 ^oC) to H₂S (-60.7 ^oC), (b) H₂S (-60.7 ^oC) to H₂Se (-40 ^oC), (c) H₂Se (-40 ^oC) to H₂Te (-2 ^oC).

20. A friend says that water is a good conductor of electricity. What would you tell them?

21. (a) How are ionic bonds formed? (b) Write the formulas for four compounds that have ionic bonds.

22. The density of an object was experimentally determined five times. The results were 1.8, 2.1, 1.99, 2.26, and 2.2 g/mL. What would you report as the density of the object?

23. What is the purpose of a college education? How can this course help to accomplish this purpose? Explain.

1. (a) Predict the graph for an experiment that determines density by changing mass at a constant volume. (b) Predict the graph for an experiment that determines density by changing volume given a constant mass.

2. If a 2.5 kg ball is dropped from rest at a height of 2.0 m, how much kinetic energy does the ball have when at a height of (a) 1.5 m, (b) 1.0 m, (c) 0.5 m, (d) 0.0 m? Assume no heat or other energy is produced.

3. What is the velocity of the ball at each height in problem two?

4. If 5 J of heat is produced during every 0.5 m that the ball travels, what will the kinetic energy of the ball be at each of the heights given in problem two?

5. How much heat is generated if a 3.0 kg ball dropped from rest falls 4.0 m and has 100 J of kinetic energy after falling that 4 m?

6. Explain how a rocket can change directions in outer space.

7. If a person stands on a platform that is able to rotate without friction, points a cordless drill toward the sky, and then turns it on, what will happen. Explain.