According to the kinetic molecular theory, what is most likely to occur when the molecules in a gas slow down?

• A. The gas expands to fill a larger volume.
• B. The pressure of the gas increases.
• C. The temperature of the gas decreases.
• D. The molecules gain kinetic energy.

Answer: (C)

Verified step by step guidance

1. Recall that according to the kinetic molecular theory, the temperature of a gas is directly related to the average kinetic energy of its molecules. This means that if the molecules slow down, their kinetic energy decreases.
2. Understand that kinetic energy (KE) of a molecule is given by the equation \(KE = \frac{1}{2}mv^2\), where \(m\) is the mass of the molecule and \(v\) is its velocity. Slower molecules have lower velocity, so their kinetic energy decreases.
3. Since temperature is a measure of the average kinetic energy of gas molecules, a decrease in molecular speed corresponds to a decrease in temperature.
4. Consider the other options: expansion to fill a larger volume would require molecules to move faster or the container to change, and an increase in pressure would require molecules to collide more frequently or forcefully, which is not consistent with slowing down.
5. Therefore, the most likely outcome when gas molecules slow down is that the temperature of the gas decreases.