According to the kinetic molecular theory, if the molecules of a gas sample speed up, which of the following will most likely occur?

• A. The average kinetic energy of the molecules will decrease.
• B. The volume of the gas will decrease at constant pressure.
• C. The temperature of the gas will increase.
• D. The pressure of the gas will decrease at constant volume.

Answer: (C)

Verified step by step guidance

1. Recall that according to the kinetic molecular theory, the average kinetic energy of gas molecules is directly proportional to the absolute temperature of the gas. This means if the molecules speed up, their average kinetic energy increases.
2. Understand that temperature is a measure of the average kinetic energy of the molecules. Therefore, if the molecules speed up, the temperature of the gas must increase.
3. Consider the relationship between volume, pressure, and temperature. At constant pressure, if the molecules speed up (temperature increases), the volume tends to increase, not decrease, according to Charles's Law.
4. At constant volume, if the molecules speed up (temperature increases), the pressure tends to increase, not decrease, according to Gay-Lussac's Law.
5. Summarize that the correct consequence of molecules speeding up is an increase in temperature, as it directly reflects the increase in average kinetic energy.