EXAMPLE EXERCISE 4.1 Change of Physical State

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.

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.

Practice Exercise

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.

Answers: (a) condensing; (b) freezing; (c) deposition

Figure 4.1 Changes in Physical State As temperature increases, a solid melts to a liquid and then vaporizes into a gas. As temperature decreases, a gas condenses to a liquid and then freezes to a solid.

Introductory Chemistry: Concepts and Critical Thinking, 6th Edition Charles H. Corwin

? 2011 Pearson Education, Inc.

EXAMPLE EXERCISE 4.1 Change of Physical State

Continued

Concept Exercise

Identify the physical state (solid, liquid, gas) that corresponds to each of the following pictorial representations:

Answer: See Appendix G.

Introductory Chemistry: Concepts and Critical Thinking, 6th Edition Charles H. Corwin

? 2011 Pearson Education, Inc.

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.

Introductory Chemistry: Concepts and Critical Thinking, 6th Edition Charles H. Corwin

Figure 4.2 Classification of Matter Matter may be either a mixture or a pure substance. The properties of a heterogeneous mixture vary within the sample (oil and water). The properties of a homogeneous mixture are constant (salt solution). A pure substance may be either a compound (water) or an element (gold). Left to right: oil and water; NaCl solution; H2O; and gold nugget.

? 2011 Pearson Education, Inc.

EXAMPLE EXERCISE 4.2 Element, Compound, or Mixture

Continued

Practice Exercise

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 ore

(d) dental alloy

Answers: (a) element; (b) compound; (c) heterogeneous mixture; (d) homogeneous mixture

Introductory Chemistry: Concepts and Critical Thinking, 6th Edition Charles H. Corwin

? 2011 Pearson Education, Inc.

EXAMPLE EXERCISE 4.2 Element, Compound, or Mixture

Continued

Concept Exercise

Classify each of the following as an element, a compound, or a mixture as shown in the illustration:

Answer: See Appendix G.

Introductory Chemistry: Concepts and Critical Thinking, 6th Edition Charles H. Corwin

? 2011 Pearson Education, Inc.

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

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.

Introductory Chemistry: Concepts and Critical Thinking, 6th Edition Charles H. Corwin

? 2011 Pearson Education, Inc.

EXAMPLE EXERCISE 4.3 Properties of Metals

Continued

Practice Exercise

Which of the following properties is not characteristic of a

nonmetal?

(a) insulator of electricity (b) ductile

(c) low density

(d) reacts with nonmetals

Answer: (b) Nonmetals crush to a powder and are not malleable or ductile.

Concept Exercise

Which of the following is a solid metal under normal conditions: calcium, phosphorus, mercury, or silicon? (Refer to Figure 4.7.)

Answer: See Appendix G.

Figure 4.7 Pictorial Periodic Table of the Elements The natural abundance is the percent by mass of an element in Earth's crust, oceans, and atmosphere. The natural abundance of an element listed as rare is less than 1 mg per metric ton (1000 kg). An element listed as synthetic is made artificially and does not occur naturally. An element listed as unstable often disintegrates in a fraction of a second.

Introductory Chemistry: Concepts and Critical Thinking, 6th Edition Charles H. Corwin

? 2011 Pearson Education, Inc.

EXAMPLE EXERCISE 4.4 Physical States 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

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.

Figure 4.5 Metals, Nonmetals, and Semimetals The symbols of elements having metallic properties are on the left side of the periodic table, nonmetallic are on the right side, and semimetallic are midway between. Notice the special placement of hydrogen, a nonmetallic element.

Introductory Chemistry: Concepts and Critical Thinking, 6th Edition Charles H. Corwin

? 2011 Pearson Education, Inc.

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download