NCCER Millwright Practice Exam

As the temperature of a gas increases, what happens to the molecules within it?

1. They move slower

2. They become denser

3. They move faster

4. They form a solid

The correct answer is: They move faster

When the temperature of a gas increases, the kinetic energy of its molecules also increases. This results in the molecules moving faster and colliding with one another more frequently and with greater energy. The basic principle behind this behavior stems from the kinetic molecular theory, which posits that temperature is a measure of the average kinetic energy of the molecules in a substance. As the temperature rises, the energy provided to the molecules causes them to overcome intermolecular forces and thus increases their speed. This increased molecular motion is what leads to a greater volume for gases, as they tend to expand when heated. Understanding this relationship is crucial for applications in mechanical systems where gas behavior is relevant, such as in engines and compressors.