1.1.5.b. First Law of Thermodynamics

The first law of thermodynamics states that the change in the internal energy of a system is equal to the difference in energy transferred to or from the system as heat and

• mass
• work done
• force
• pressure

The first law of thermodynamics is a restatement of the

• Zeroth Law of Thermodynamics

• Law of Heat Addition

• Principle of Entropy

• Law of Conservation of Energy

When applying the first law of thermodynamics to a system, when is heat a positive quantity?

• when the system does work
• when the system has work done on it
• when the system absorbs heat
• when the system loses heat
• when no work is done either on the system or by the system

A pump full of compressed gas is allowed to expand and 80 kJ of work is done by the gas on an object in the lab. At the same time, the gas is warmed by the addition of 100 J of heat energy. If the initial internal energy of the gas is 500 kJ, calculate the final internal energy.

• 500 kJ

• 80 kJ

• 100 kJ

• 520 kJ

A foam cup is filled with hot water and allowed to cool while being stirred by a paddlewheel. Initially the water has an internal energy of 200 kJ, and while cooling it loses 150 kJ of heat. The paddlewheel does 25 kJ of work on the water.

Calculate the change in internal energy of the water.

• -150 kJ

• -125 kJ

• 75 kJ

• 200 KJ

A foam cup is filled with hot water and allowed to cool while being stirred by a paddlewheel. Initially the water has an internal energy of 200 kJ, and while cooling it loses 150 kJ of heat. The paddlewheel does 25 kJ of work on the water.

Calculate the final internal energy of the water.

• -150 kJ

• -125 kJ

• 75 kJ

• 200 KJ

Calculate the change in internal energy of a system that does 1.20 MJ of work (out) while 4.8 MJ of

heat transfer occurs (out) to the environment. Assume no other changes (such as temperature or by the addition of fuel) take place.

• -3.6 MJ

• 3.6 MJ

• -6.0 MJ

• 6.0 MJ

During a thermodynamic process, 200 kJ of heat is added to a system, and the system performs 120 kJ of work. What is the change in internal energy of the system?

• 80 kJ

• 320 kJ

• -80 kJ

• 200 kJ

In a closed system undergoing an adiabatic process, if the system does 150 kJ of work, how does this affect the internal energy of the system?

• Increases by 150 kJ

• Decreases by 150 kJ

• Remains unchanged

• Increases by 300 kJ

A refrigerator removes 500 kJ of heat from its interior at a work cost of 150 kJ. What is the change in internal energy of the refrigerator?

• -350 kJ

• 350 kJ

• -650 kJ

• 650 kJ