Internal energy is the total energy contained within a system, including the kinetic and potential energy of the particles that make up the system.
Gas expands when its molecules increase in kinetic energy and move further apart, causing an increase in volume. This can happen when the gas is heated or when pressure is released from a container.
As gas expands, its internal energy also increases. This is because the molecules are gaining kinetic energy and moving further apart, resulting in an increase in the total energy of the system.
The internal energy of a gas is affected by its temperature, pressure, and volume. Changes in these factors can lead to changes in the internal energy of the gas.
The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or converted. This applies to internal energy, as any changes in the internal energy of a gas must be accounted for by changes in other forms of energy, such as heat or work. Therefore, the first law of thermodynamics is directly related to the changes in internal energy that occur during gas expansion.