SAT Subject Physics Practice Question 649: Answer and Explanation
15. Which of the following statements is true about an ideal gas contained at a fixed volume when its temperature is raised?
A. The density of the gas decreases.
B. The average velocity of the gas particles increases.
C. The density of the gas increases.
D. The pressure remains constant.
E. The pressure decreases.
Correct Answer: B
The correct answer is (B). The temperature of a gas is directly related to the rate at which gas particles strike the sides of the container in which the gas is contained. The measure of the number of times gas particles strike the sides of the container is pressure. Charles Law shows the direct relationship between the two. When the temperature increases, the pressure increases. This means the velocity of the gas particles increases, too.