91Ó°ÊÓ

The density of water at \(4.00^{\circ} \mathrm{C}\) is \(1.00 \mathrm{~g} / \mathrm{mL}\). The density of ice at \(0{ }^{\circ} \mathrm{C}\) is \(0.917 \mathrm{~g} / \mathrm{mL}\). Water is different from most other substances in that the solid phase (ice) is less dense than the liquid phase. Explain why this characteristic makes ice fishing possible.

How many significant figures are there in each number: (a) \(5.300 \times 10^{-2}\) (b) \(3.2 \times 10^{5}\) (c) \(0.00890 \times 10^{-4}\) (d) \(7.9600000 \times 10^{10}\) (e) \(8.030 \times 10^{21}\)

Explain what effect compressing a gas has on the density of the gas.

A rock is experimentally determined to be \(3.5\) billion years old, with an uncertainty of plus on minus 100,000 years. Write the age of this rock in scientific notation.

A student uses a digital balance to determine the mass of an object. Its digital display reads \(2.635 \mathrm{~g}\). He keeps looking at the balance and it stays fixed at \(2.635 \mathrm{~g}\) for half an hour. He then states, "The mass of the object is \(2.635 \mathrm{~g}\) exactly. There is no uncertainty in this measurement because the last digit '5' stayed constant and did not change over time." Is he right? Is the mass of the object exactly known with no uncertainty? Explain.

Without doing any numerical calculations, determine which would have the smallest volume: (a) \(50 \mathrm{~g}\) of water (density \(=1.0 \mathrm{~g} / \mathrm{mL}\) ) (b) \(50 \mathrm{~g}\) of salt water (density \(=2.3 \mathrm{~g} / \mathrm{mL}\) ) (c) \(50 \mathrm{~g}\) of mercury (density \(=13.6 \mathrm{~g} / \mathrm{mL}\) ) (d) \(50 \mathrm{~g}\) of alcohol (density \(=0.89 \mathrm{~g} / \mathrm{mL}\) ) Explain your reasoning.