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Unformatted text preview: 1 Introduction: Matter and Measurement Visualizing Concepts 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 Measurements (darts) that are close to each other are precise . Measurements that are close to the true value (the bulls eye) are accurate . (a) Figure ii represents data that are both accurate and precise. The darts are close to the bulls 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 bulls eye. (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 bulls eye. 1.6 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. 1.7 In order to cancel units, the conversion factor must have the unit being canceled opposite the starting position. For example, if the unit cm starts in the numerator, then the conversion factor must have cm in its denominator. However, if the unit cm starts in the denominator, the conversion factor must have cm in the numerator. Ideally, this will lead to the desired units in the appropriate location, numerator or denominator. However, the inverse of the answer can be taken when necessary. Classification and Properties of Matter 1.10 (a) homogeneous mixture (b) heterogeneous mixture (particles in liquid) 1 1 Matter and Measurement Solutions to Black Exercises (c) pure substance (d) heterogeneous mixture 1.12 (a) C (b) Na (c) F (d) Fe (e) P (f) Ar (g) Ni (h) Ag 1.14 (a) cobalt (b) iodine (c) krypton (d) mercury (e) arsenic (f) titanium (g) potassium (h) germanium 1.16 Before modern instrumentation, the classification of a pure substance as an element was...
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