1. Ch. 17 Elements of Chemistry
Unit Test Review

2. Phases of matter

3. Physical Changes

4. Physical Properties

5. Chemical Changes

6. Physical changes at the atomic level

7. Chemical changes

8. Which is a chemical change?

9. Which is a physical change? Which is a chemical change? explain

10. Characteristics of metals, metalloids, and non-metals

11. What are compounds?

12. Do elements have the same properties as the compound?

14. Which is element and which is a compound?

15. Is this a physical change or a chemical change?

16. Guidelines for naming compounds:
The name of the element farther to the left in the periodic table is followed by the name of the element farther to the right. Add the suffix “-ide”. Ex. Li2O lithium oxide
Prefixes for different numbers of the same element:
1 = mono, 2 = di, 3 = tri, and 4 = tetra.
Example: CO is carbon monoxide
Hydrogen peroxide is H2O2 name is dihydrogen dioxide
Many compounds have common names like: H2O = water,
NH3 = ammonia, and CH4 = methane.

17. 1. Water molecules vibrate and jostle about at different speeds depending upon where they are located. Rank the speed of water molecules found in a steam-hot geyser, a frozen glacier, and a flowing river.
In order of increasing speed: a frozen glacier, a flowing river, a steam-hot geyser.

18. 1. Is chemistry the study of the submicroscopic, the microscopic, the macroscopic, or all three? Defend your answer.
Chemistry is the careful study of matter and can take place at a number of different levels including the submicroscopic, microscopic, or macroscopic levels.

19. Think and Explain
2. Of the three sciences physics, chemistry, and biology, which is the most complex?
Biology is based upon the principles of chemistry as applied to living organisms, while chemistry is based upon the principles of physics as applied to atoms and molecules. Physics is the study of the fundamental rules of nature, which more often than not are rather simple in their design and readily described by mathematical formula. Because biology sits at the top of these three sciences, it can be considered to be the most complex of them all.

20. 4. A cotton ball is dipped in alcohol and wiped across a table top
4. A cotton ball is dipped in alcohol and wiped across a table top. Explain what happens to the alcohol molecules deposited on the table top? Is this a physical or chemical change?
The molecules of the alcohol evaporate into the gaseous phase, which is a physical change.

21. 6. Red-colored Kool-aid crystals are added to a still glass of water
6. Red-colored Kool-aid crystals are added to a still glass of water. The crystals sink to the bottom. Twenty four hours later the entire solution is red even though no one stirred the water. Explain. Even though the water appears to be still, the water molecules are bustling with kinetic energy. The red dye of the Kool-aid gets knocked around by these molecules to the point that the dye is eventually dispersed throughout the water. This is another case where the existence of molecules helps to explain the observed phenomenon.

22. 7. Red-colored Kool-aid crystals are added to a still glass of hot water. The same amount of crystals are added to a second still glass filled with the same amount of cold water. With no stirring, which would you expect to become uniform in color first: the hot water or the cold water? Why?
The dye should become dispersed uniformly within the hot water first. The higher the temperature, the greater the average kinetic energy of the molecules. Because the molecules within the hot water are moving faster they have a quicker effect on the dye of the Kool-aid crystals. Furthermore, the hot water will tend to have more convection currents that will also help to distribute the dye throughout the water.

23. 8. Which has stronger attractions among its submicroscopic particles: a solid at 25°C or a gas of a different substance at 25°C? Explain.
At 25°C there is a certain amount of thermal energy available to all the submicroscopic particles of a material. If the attractions between the particles are not strong enough, the particles may separate from each other to form a gaseous phase. If the attractions are strong, however, the particles may be held together in the solid phase. We can assume, therefore, that the attractions among the submicroscopic particles of a material in its solid phase at 25°C are stronger than they are within a material that is a gas at this temperature.

24. 9. Which occupies the greatest volume: 1 gram of ice, 1 gram of liquid water, or 1 gram of water vapor? One gram of water vapor, the gaseous phase of water, occupies the most space.

25. 12. Classify the following changes as physical or chemical
12. Classify the following changes as physical or chemical. Even if you are incorrect in your assessment, you should be able to defend why you chose as you did.
a. grape juice turns to wine —————
b. wood burns to ashes —————
c. water begins to boil —————
d. a broken leg mends itself —————
e. grass grows —————
f. an infant gains 10 pounds —————
g. a rock is crushed to powder —————
a) chemical. b) chemical. c) physical. d) chemical. e) chemical. f) chemical. g) physical.

26. 13. What physical and chemical changes occur when a wax candle burns?
The melting of the wax near the flame is an example of a physical change. This liquid wax is drawn up the wick where it is burned, which is an example of a chemical change.

27. 15. Why not memorize the periodic table
15. Why not memorize the periodic table? The periodic table is a reference to be used, not memorized. You need not memorize the periodic table any more than you need to memorize a dictionary. Both the periodic table and the dictionary should be readily available to you when you need them.

28. 16. Why is water not classified as an element?
Water use to be classified as an element but that was before people recognized that the basic building block of matter are these tiny particles called atoms. Today, an element is identified as a material consisting only one kind of atom.

29. 17. Oxygen atoms are used to make water molecules
17. Oxygen atoms are used to make water molecules. Does this mean that oxygen, O2, and water, H2O, have similar properties? All the oxygen present in this material is bound to hydrogen atoms making water molecules. This water is uniquely different from the elements oxygen, O2, and hydrogen, H2, from which it is made. The oxygen our bodies are designed to breathe is gaseous molecular oxygen, O2. We drown when we breathe in water because it contains so little O2. Although they both contain oxygen, gaseous oxygen, O2, and water, H2O, are vastly different materials.

30.  18. What is the chemical formula for the compound dihydrogen sulfide?
H2S.

31. 19. What is the chemical name for a compound with the formula Ba3 N2?
Tribarium dinitride, or more simply, barium nitride because no ratio other than three bariums to two nitrogens is possible.