First Law of Thermodynamics

If a system has 200 J of heat added to it and does 150 J of work, what is the change in internal energy?

What does it mean if ΔU is zero in a thermodynamic process?

A gas is compressed in a cylinder, and 100 J of work is done on the gas. The gas loses 60 J of heat. What is ΔU?

• –160 J

• –40 J

• +40 J

• +160 J

During an adiabatic process, no heat is exchanged with the surroundings. How is the first law written?

A system absorbs 500 J of heat and its internal energy increases by 300 J. How much work did the system do?

In an isothermal process, temperature remains constant, so ΔU = 0.

In an isobaric expansion, a gas does 250 J of work and gains 400 J of heat. What happens to the internal energy?

Match the process with the correct thermodynamic condition:

• Adiabatic → No heat transfer → Q = 0

• Isothermal → Constant temperature → ΔU = 0

• Isochoric → No volume change → W = 0

• Isobaric → Constant pressure

A gas in a sealed, rigid container is heated with 100 J of energy. What is the work done by the gas?

• 0 J

• 100 J

• –100 J

• Cannot be determined

A gas expands and does 75 J of work while its internal energy decreases by 25 J. How much heat was added or removed?