1. Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Introductory Chemistry: Concepts & Connections, Fifth Edition By Charles H. Corwin Example Exercise 4.1 Change of Physical State State the term that applies to each of the following changes of physical state. (a) Snow changes from a solid to a liquid. (b) Gasoline changes from a liquid to a gas. (c) Dry ice changes from a solid to a gas. State the term that applies to each of the following changes of physical state. (a) A refrigerant changes from a gas to a liquid. (b) Water changes from a liquid to a solid. (c) Iodine vapor changes from a gas to a solid. Practice Exercise Solution Refer to Figure 4.1 for the changes of physical state. (a) The change from solid to liquid is called melting. (b) The change from liquid to gas is called vaporizing. (c) The change from solid to gas is called sublimation Answers: (a) condensing; (b) freezing; (c) deposition See end-of-chapter Key Concept Exercise 1. Concept Exercise

2. Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Introductory Chemistry: Concepts & Connections, Fifth Edition By Charles H. Corwin Example Exercise 4.2 Element, Compound, or Mixture Consider the following properties of the element copper. (a) Copper metal cannot be broken down by a chemical change. (b) Copper reacts with oxygen in air to give copper oxide. (c) Copper, in the form of malachite ore, is found worldwide. (d) Copper and tin compose bronze alloy. Classify each of the following copper samples as an element, a compound, a homogeneous mixture, or a heterogeneous mixture. (a) copper wire (b) copper oxide (c) malachite ore (d) bronze alloy Solution Refer to Figure 4.2 to classify each sample. (a) Copper wire is a metallic element. (b) Copper oxide is a compound of the elements copper and oxygen. (c) Malachite ore is a heterogeneous mixture of copper and other substances. (d) Bronze alloy is a homogeneous mixture of copper and tin.

3. Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Introductory Chemistry: Concepts & Connections, Fifth Edition By Charles H. Corwin Example Exercise 4.2 Element, Compound, or Mixture Consider the following properties of the element mercury. (a) Mercury liquid cannot be broken down by a chemical change. (b) Mercury oxide can be heated to give mercury and oxygen gas. (c) Mercury, in the form of cinnabar ore, is found in Spain and Italy. (d) Mercury and silver compose the alloy used for dental fillings. Classify each of the following mercury samples as an element, a compound, a homogeneous mixture, or a heterogeneous mixture. (a) mercury liquid (b) mercury oxide (c) cinnabar one (d) dental alloy Practice Exercise Answers: (a) element (b) compound (c) heterogeneous mixture(d) homogeneous mixture See end-of-chapter Key Concept Exercise 2 and 3. Concept Exercise

4. Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Introductory Chemistry: Concepts & Connections, Fifth Edition By Charles H. Corwin Example Exercise 4.3 Properties of Metals Which of the following properties is not characteristic of a metal? (a) good conductor of heat (b) malleable (c) high melting point (d) reacts with other metals Which of the following properties is not characteristic of a nonmetal? (a) insulator of electricity (b) ductile (c) low density (d) reacts with nonmetals Practice Exercise Solution Refer to Table 4.4 to classify each of the following properties. (a) Metals are good conductors of heat. (b) Metals are malleable. (c) Metals usually have high melting points. (d) Metals do not react with other metals; they mix to form alloys. Answers: (b) Nonmetals crush to a powder and are not malleable or ductile. See end-of-chapter Key Concept Exercise 4. Concept Exercise

5. Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Introductory Chemistry: Concepts & Connections, Fifth Edition By Charles H. Corwin Example Exercise 4.4 Physical State of the Elements Indicate the physical state for each of the following elements at 25 °C and normal pressure; classify each element as a metal, nonmetal, or semimetal. (a) barium (b) boron (c) bismuth (d) bromine Indicate the physical state for each of the following elements at 25 °C and normal pressure; classify each element as a metal, nonmetal, or semimetal. (a) aluminum (b) hydrogen (c) helium (d) radium Practice Exercise Solution Referring to Figures 4.5 and 4.6, we observe the following. (a) Barium (Ba) is on the left side of the periodic table; it is a solid metal under normal conditions. (b) Boron (B) is in the middle of the periodic table; it is a solid semimetal. (c) Bismuth (Bi) is to the right but below the semimetals in the periodic table. It is a solid metal. (d) Bromine (Br) is on the right side of the periodic table; it is a liquid nonmetal at normal conditions. Answers: (a) solid metal; (b) gaseous nonmetal; (c) gaseous nonmetal; (d) solid metal See end-of-chapter Key Concept Exercise 5. Concept Exercise

6. Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Introductory Chemistry: Concepts & Connections, Fifth Edition By Charles H. Corwin Example Exercise 4.5 Composition of Chemical Formulas State the total number of atoms in a molecule of vitamin, B 3 C 6 H 6 N 2 O. Write the chemical formula for vitamin B 6, if a molecule is composed of 8 carbon atoms, 11 hydrogen atoms, 1 nitrogen atom, and 3 oxygen atoms. Practice Exercise Solution The chemical formula for vitamin B 3 indicates 6 carbon atoms, 6 hydrogen atoms, 2 nitrogen atoms, and 1 oxygen atom. Thus, C 6 H 6 N 2 O has a total of 15 atoms. Answers: C 8 H 11 NO 3 (total of 23 atoms) See end-of-chapter Key Concept Exercise 6. Concept Exercise

7. Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Introductory Chemistry: Concepts & Connections, Fifth Edition By Charles H. Corwin Example Exercise 4.6 Composition of Chemical Formulas State the total number of atoms in a molecule of glycerin, C 3 H 5 (OH) 3 Write the chemical formula for nitroglycerin if a molecule is composed of 3 carbon atoms, 5 hydrogen atoms, 3 oxygen atoms, and 3 NO 2 units. Practice Exercise Solution The chemical formula for glycerin indicates 3 carbon atoms, 5 hydrogen atoms, and 3 OH units. Thus, C 3 H 5 (OH) 3 has a total of 14 atoms. Answers: C 3 H 5 (OH) 3 (20 atoms total) See end-of-chapter Key Concept Exercise 6. Concept Exercise

8. Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Introductory Chemistry: Concepts & Connections, Fifth Edition By Charles H. Corwin Example Exercise 4.7 Physical and Chemical Properties Classify each of the following properties as physical or chemical. (a) Water appears colorless and odorless at 20 °C. (b) Water dissolves sucrose crystals. (c) Water produces a gas with calcium metal. (d) Water exists as ice at -10 °C. Classify each of the following properties as physical or chemical. (a) Water appears hard and crystalline at 0 °C. (b) Water is insoluble in gasoline. (c) Water is a very weak conductor of electricity. (d) Water produces a gas with calcium metal. Practice Exercise Solution If a reaction occurs, there is a change in composition and the property is chemical. Otherwise, the property is physical. (a) Color and odor are physical properties. (b) Solubility is a physical property. (c) A chemical reaction is a chemical property. (d) A physical state is a physical property. Answers: (a) physical; (b) physical; (c) physical; (d) chemical See end-of-chapter Key Concept Exercise 7. Concept Exercise

9. Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Introductory Chemistry: Concepts & Connections, Fifth Edition By Charles H. Corwin Example Exercise 4.8 Physical and Chemical Changes Classify each of the following observations as a physical or a chemical change. (a) Touching a match to hydrogen soap bubbles gives an explosion. (b) Heating water in a flask produces moisture on the glass. (c) Combining two colorless solutions gives a yellow solid. (d) Pouring vinegar on baking soda produces gas bubbles Classify each of the following observations as a physical or a chemical change. (a) Freezing water in a refrigerator makes cubes of ice. (b) Adding silver nitrate to tap water gives a cloudy solution. (c) Burning sulfur gives a light blue flame. (d) Grinding aspirin tablets produces a powder. Practice Exercise Solution An observation that indicates a physical change is a change of physical state. The observations that suggest a chemical change include burning, fizzing, changing color, or forming an insoluble substance in solution. (a) Hydrogen explodes; thus, it is a chemical change. (b) Water is boiled; thus, it is a physical change. (c) Two solutions give an insoluble substance; thus, it is a chemical change. (d) Baking soda fizzes; thus, it is a chemical change. Answers: (a) physical; (b) chemical; (c) chemical; (d) physical See end-of-chapter Key Concept Exercise 8. Concept Exercise

10. Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Introductory Chemistry: Concepts & Connections, Fifth Edition By Charles H. Corwin Example Exercise 4.9 Conservation of Mass Law In an experiment, 2.430 g of magnesium metal was ignited and burned with oxygen in the air. If 4.030 g of white magnesium oxide powder, MgO, was collected, what was the mass of oxygen gas that reacted? If 0.654 g of zinc metal reacts with 0.321 g of yellow powdered sulfur, what is the mass of the zinc sulfide produced? Practice Exercise Solution Applying the conservation of mass law, we find that the mass of the magnesium metal plus the mass of the oxygen gas equals the mass of the magnesium oxide powder. That is, 2.430 g Mg + mass of oxygen = 4.030 g MgO mass of oxygen = 4.030 g MgO - 2.430 g Mg mass of oxygen = 1.600 g Answers: 0.975 g See end-of-chapter Key Concept Exercise 9. Concept Exercise

11. Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Introductory Chemistry: Concepts & Connections, Fifth Edition By Charles H. Corwin Example Exercise 4.10 Kinetic Energy and Molecular Motion A balloon filled with helium gas is cooled from 25 ºC to -25º C. State the change in each of the following. (a) kinetic energy of the gas (b) motion of helium atoms A steel cylinder containing air is heated from 25 °C to 50 °C. State the change in each of the following. (a) kinetic energy of the gas (b) motion of air molecules Practice Exercise Solution Temperature, kinetic energy, and velocity are related as follows. (a) As the temperature cools from 25 °C to -25 °C, the kinetic energy of helium atoms decreases. (b) Since a drop in temperature produces a decrease in kinetic energy, the motion of helium atoms decreases. Answers: (a) increases; (b) increases See end-of-chapter Key Concept Exercise 10. Concept Exercise

12. Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Introductory Chemistry: Concepts & Connections, Fifth Edition By Charles H. Corwin Example Exercise 4.11 Forms of Energy Identify two forms of energy that are involved in each of the following conversions. (a) radioactive emissions vaporize water to steam (b) steam drives a turbine (c) a turbine spins and drives an electrical generator Identify two forms of energy that are involved in each of the following devices. (a) Flashlight (b) solar calculator (c) lead–acid battery Practice Exercise Solution We can refer to the six forms of energy listed above. It follows that (a) nuclear energy is converted to heat energy. (b) heat energy is converted to mechanical energy. (c) mechanical energy is converted to electrical energy. Answers: (a) chemical and light; (b) light and electrical; (c) chemical and electrical See end-of-chapter Key Concept Exercise 11. Concept Exercise