How does the change in internal energy relate to heat and work in a system?

The change in internal energy of a system is equal to the heat added to the system minus the work done by the system.

When heat is added to a system, the internal energy of the system increases. This is because the heat energy is transferred to the particles within the system, causing them to move faster and increase their kinetic energy. The increase in internal energy can be calculated using the equation ΔU = Q - W, where ΔU is the change in internal energy, Q is the heat added to the system, and W is the work done by the system.

Similarly, when work is done by a system, the internal energy of the system decreases. This is because the work energy is transferred from the particles within the system to the surroundings, causing them to lose kinetic energy and decrease their internal energy. The decrease in internal energy can also be calculated using the same equation, ΔU = Q - W, where ΔU is now negative.

Therefore, the change in internal energy of a system is directly related to the heat added to the system and the work done by the system. If the system absorbs more heat than it does work, the internal energy of the system will increase. Conversely, if the system does more work than it absorbs heat, the internal energy of the system will decrease.