Answer the question briefly and the point:
Which type of motion of the molecules is responsible for the internal energy of a monoatomic gas?

Explanation

To answer the question regarding which type of motion of the molecules is responsible for the internal energy of a monoatomic gas, we can follow these steps:

1. **Understanding Internal Energy**: Internal energy refers to the total energy contained within a system. For gases, this energy primarily arises from the motion of the gas molecules.

2. **Types of Molecular Motion**: In a monoatomic gas, the molecules are considered to be point particles. The types of motion that can contribute to internal energy include translational, rotational, and vibrational motion. However, for monoatomic gases, only translational motion is significant.

3. **Kinetic Theory of Gases**: According to the kinetic theory of gases, it is assumed that gas molecules are in constant random motion and that there are no intermolecular forces acting between them. This means that the potential energy is negligible, and the internal energy is primarily due to the kinetic energy of the molecules.

...