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Chapter01rw-final

# Chapter01rw-final - 1 1.1(a(b(c(d 1.2 Introduction Matter...

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1 1 Introduction: Matter and Measurement Visualizing Concepts 1.1 Pure elements contain only one kind of atom. Atoms can be present singly or as tightly bound groups called molecules. Compounds contain two or more kinds of atoms bound tightly into molecules. Mixtures contain more than one kind of atom and/or molecule, not bound into discrete particles. (a) pure element: i, v (b) mixture of elements: vi (c) pure compound: iv (d) mixture of an element and a compound: ii, iii 1.2 After a physical change , the identities of the substances involved are the same as their identity before the change. That is, molecules retain their original composition. During a chemical change , at least one new substance is produced; rearrangement of atoms into new molecules occurs. The diagram represents a chemical change , because the molecules after the change are different than the molecules before the change. 1.3 (a) time (b) density (c) length (d) area (e) temperature (f) volume (g) temperature 1.4 Density is the ratio of mass to volume. For a sphere, size is like volume both are determined by the radius of the sphere. For spheres of the same size or volume, the denominator of the density relationship is the same. The denser the sphere, the heavier it is. A list from lightest to heaviest is in order of increasing density and mass. The alu- minum sphere (density = 2.70 g/cm 3 ) is lightest, then nickel (density = 8.90 g/cm 3 ), then silver (density = 10.409 g/cm 3 ). 1.5 Measurements (darts) that are close to each other are precise . Measurements that are close to the “true value” (the bull’s eye) are accurate . (a) Figure ii represents data that are both accurate and precise. The darts are close to the bull’s eye and each other. (b) Figure i represents data that are precise but inaccurate. The darts are near each other but their center point (average value) is far from the bull’s eye.

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1 Matter and Measurement Solutions to Exercises 2 (c) Figure iii represents data that are imprecise but their average value is accurate. The darts are far from each other, but their average value, or geometric center point, is close to the bull’s eye. 1.6 (a) 7.5 cm. There are two significant figures in this measurement; the number of cm can be read precisely, but there is some estimating (uncertainty) required to read tenths of a centimeter. Listing two significant figures is consistent with the convention that measured quantities are reported so that there is uncertainty in only the last digit. (b) 140 ° F. The temperature can be read to the nearest 50 ° F and estimated to the nearest 5–10 ° F. Since there is uncertainty in the tens digit, the measurement has two significant figures. 1.7 The determined age of the artifact, 1,900 years, has two significant figures. There is uncertainty in the hundreds place, indicating that the minimum uncertainty in age is 100 years. The 20-year period since the age was determined is not significant relative to the determined age.
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Chapter01rw-final - 1 1.1(a(b(c(d 1.2 Introduction Matter...

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