Give two ways in which the internal energy of the system can be changed?

1. By adding or removing heat to the system: When heat is added to a system, the internal energy of the system increases as the molecules within the system gain kinetic energy. Conversely, when heat is removed from a system, the internal energy decreases as the molecules lose kinetic energy.

2. By doing work on or by the system: Work can also change the internal energy of a system. For example, compressing a gas by applying pressure to it can increase the internal energy of the system, while allowing the gas to expand and do work on its surroundings can decrease the internal energy of the system.

1. Heat Transfer
2. Work Done