18.1. Temperature http://www.ck12.org
1
2
mv^2 =3
2
kTv=√
3 kT
mv=√
3 ∗ 1. 38 ∗ 10 −^23 J/K∗100 K
3. 34 ∗ 10 −^26 kg
v= 352 .1 m/sExplore More
- Convert the boiling point of water 100◦C to Fahrenheit
- Convert 70◦F to Celsius
- The temperature of the box is related to the average speed of the molecules. Use momentum principles to
relate temperature to pressure. Explain conceptually, in words rather than with equations. - Explain why a lake freezes at the top first, rather than throughout or at the bottom?
- Typical room temperature is about 300 K. As you know, the air in the room contains bothO 2 andN 2 gases,
with nitrogen the lower mass of the two. If the average kinetic energies of the oxygen and nitrogen gases are
the same (since they are at the same temperature), which gas has a higher average speed? - Temperature is a measure of the average kinetic energy of molecules. Consider a mixture of hydrogen and
oxygen gas at a certain temperature. Use the formula for kinetic energy to explain why the hydrogen molecules
move faster than the oxygen molecules. Then explain why there’s no hydrogen in the earth’s atmosphere, and
why the moon has no atmosphere at all. - Calculate the average speed ofN 2 molecules at room temperature(300 K). (You remember from your
chemistry class how to calculate the mass (inkg) of anN 2 molecule, right?) - How high would the temperature of a sample ofO 2 gas molecules have to be so that the average speed of the
molecules would be 10% the speed of light? Convert this temperature to Kelvin and Fahrenheit as well.
Answers to Selected Problems- 212◦F