Internal Energy Change in a System

Internal energy is the total energy contained by a system. It is the sum of the kinetic and potential energy of the particles that make up the system. When a system absorbs or releases heat or does work, the internal energy of the system changes. The relationship between the internal energy change, heat absorbed, and work done is given by the first law of thermodynamics.

Calculation of Internal Energy Change

To calculate the internal energy change in a system that has absorbed 2 kcal of heat and done 500 J of work, we need to use the first law of thermodynamics:

ΔU = Q - W

Where ΔU is the change in internal energy, Q is the heat absorbed by the system, and W is the work done by the system.

Substituting the given values, we get:

ΔU = 2 kcal - 500 J

We need to convert the units of heat absorbed to joules because work is given in joules. 1 kcal is equal to 4184 J. Therefore, 2 kcal is equal to 8368 J.

ΔU = 8368 J - 500 J

ΔU = 7868 J

Therefore, the internal energy change in the system is 7868 J.

Explanation

When a system absorbs heat, its internal energy increases, and when it does work, its internal energy decreases. In this case, the system has absorbed 2 kcal of heat and done 500 J of work. The work done by the system is positive because it is being done by the system on the surroundings. Therefore, the internal energy change in the system is positive. The first law of thermodynamics tells us that the change in internal energy of the system is equal to the heat absorbed by the system minus the work done by the system. By substituting the given values, we can calculate the internal energy change in the system.

7900 joule