High School Physics : Understanding the Second Law of Thermodynamics

Study concepts, example questions & explanations for High School Physics

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Example Questions

Example Question #9 : Laws Of Thermodynamics

A glass of cold water is placed in a sealed room. After an infinite amount of time, what will happen?

Possible Answers:

The water will warm to the temperature of the air

The air will cool to the temperature of the water

Both the water and the air will remain the same temperature, unless an outside force is applied

The water will warm and the air in the room will cool, until they are the same temperature

There is insufficient information to solve

Correct answer:

The water will warm and the air in the room will cool, until they are the same temperature

Explanation:

The second law of thermodynamics states that closed systems constantly move towards a state of thermal equilibrium. Since we are looking at a closed system, that means we must be moving towards a state of equilibrium. The only way that happens is if the air cools and the water warms, until they both reach a new final temperature.

Looking at this question in terms of heat transfer, we can infer that the glass of water will warm up, but there must be a transfer of heat to the glass in order for this to occur. The heat comes from the air, causing it to cool as the glass warms.

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