E is equal to W plus Q, and E represents internal energy. When the gas temperature rises, E increases. Because it is an ideal gas, e is only related to temperature, and w stands for work. A positive value indicates that the outside world does work on the gas (volume decreases), and a negative value indicates that the gas does work on the outside world (volume increases). Q means endothermic and exothermic, positive value means endothermic and negative value means exothermic.