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QUICK QUIZ 1.1

QUICK QUIZ 1.1.

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QUICK QUIZ 1.1

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  1. QUICK QUIZ 1.1 For lead and aluminum, the ratio of their atomic masses is about 8 and the ratio of their densities is about 4. This implies that a given volume of lead will contain about (a) twice the number of atoms as the same volume of aluminum, (b) half the number of atoms as the same volume of aluminum, (c) one fourth the number of atoms as the same volume of aluminum or, (d) one eighth the number of atoms as the same volume of aluminum?

  2. QUICK QUIZ 1.1 ANSWER (b). If lead and aluminum had the same number of atoms for the same given volume then their atomic mass ratio would equal their density ratio. The lesser amount (4 compared to 8) for the density ratio implies that a given volume of lead contains about half the number of atoms as the same volume of aluminum. Mathematically, one can look at the equation relating the ratios, .Verify that the units cancel in numerators and denominators to yield the correct units on the left side of the equation.

  3. QUICK QUIZ 1.2 The dimensions of two quantities must be identical if you are either (a) adding or multiplying, (b) adding or dividing, (c) subtracting or multiplying, (d) subtracting or dividing, (e) adding or subtracting, or (f) multiplying or dividing the two quantities?

  4. QUICK QUIZ 1.2 ANSWER (e). Only quantities of the same dimensions may be added or subtracted. For example, you may add inches (length dimension) to feet (length dimension) but could not add seconds (time dimension) to kilograms (mass dimension). Different dimensions may be multiplied or divided, for example it is permissible to divide feet by seconds to obtain dimensions of length/time.

  5. QUICK QUIZ 1.3 In France, a liter of gasoline costs 1.3 Euros. An American student is at a gas station in France and wants to know how many gallons of gasoline she can buy with the 41 Euros that she has in her pocket. Knowing that one liter is close to a quart and that there are 4 quarts in a gallon she reasons that she can buy (a) about 2 gallons, (b) about 5 gallons, (c) about 8 gallons, (d) about 12 gallons of gasoline?

  6. QUICK QUIZ 1.3 ANSWER (c). Converting units we have:

  7. QUICK QUIZ 1.4(end of section 1.6) In an experiment to determine the identity of an unknown sample, you measure the density of your sample to be 0.315 grams/cm3. In a chemistry and physics handbook, you find a chart listing the densities of various materials from gases to solids. Your sample is closest in density to the material in the chart with a density of (a) 10.2 grams/cm3, (b) 2.01 grams/cm3, (c) 0.002 grams/cm3, or (d) 0.315 X 10-3 grams/cm3?

  8. QUICK QUIZ 1.4 ANSWER (b). When comparing numbers representing physical data, it is best to compare the ratios or multiplicative factors of the two numbers rather than the difference of the two numbers. In terms of difference, material (c) is the closest to the unknown sample with a difference of only 0.315 - 0.002 = .313 g/cm3. However, in terms of ratios, material (b) is about 6 times denser than the unknown sample while material (c) is about 160 times less dense than the unknown. In fact, from these densities, material (c) must be a gas while material (b) is a solid and the unknown could be a solid such as Styrofoam. Another way to obtain a rough comparison between values is to look at the order of magnitude of each number. Order of magnitude values are 101, 100, 10-3, and 10-4 for materials (a), (b), (c), and (d), respectively and 10-1 for the unknown sample. Therefore, 10-1 (the unknown) is closest to 100 (material (b).

  9. QUICK QUIZ 1.5(end of section 1.7) Unlike meter sticks that measure to a precision of + 0.1 cm, Vernier calipers are devices that can measure to a precision of + 0.01 cm. In a lab experiment, your partner measures the thickness of your textbook with a meter stick and obtains a value of 4.3 cm. You then measure the thickness of the textbook using the Vernier caliper. Assuming that neither instrument is broken and that the measurements were made correctly, the value you would obtain using the Vernier caliper could be(a) 4.30 cm, (b) 4.31 cm, (c) 4.24 cm, (d) 4.43 cm, (e) 4.30 or 4.31 cm, (f) 4.30, 4.31, or 4.24 cm, (g) 4.30, 4.31, 4.24, or 4.43 cm?

  10. QUICK QUIZ 1.5 ANSWER (f). The precision of the meter stick implies that the value of 4.3 cm can vary by + 0.1 cm and therefore from a range of 4.2 to 4.4 cm. Any value within this range could be obtained by a measurement with the Vernier caliper and only the value 4.43 cm is outside of this range.

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