Chapter 17, Problem 1DQ

To determine

Why it would not make sense to use a full size glass thermometer to measure the temperature of a thimbleful of hot water.

Answer to Problem 1DQ

The thermometer measures the temperature when the water and the thermometer attains thermal equilibrium and this will mean a large amount of heat being lost from the little amount of water resulting in a very inaccurate reading.

Explanation of Solution

Thermometers measure the temperature of the material on attaining thermal equilibrium with it.

The temperature of thimbleful of hot water is to be measured here. The amount of water is very small. The water will have a considerable amount of heat which will be transferred to the thermometer for the instrument to reach the same temperature as the water, so that the reading will be true.

On using a full size glass thermometer, the amount of heat to be taken from the water to attain thermal equilibrium will be much greater. This will result in a much lesser temperature reading than the original temperature of the water. Therefore the thermometer should also be of comparable dimensions.

Conclusion:

Therefore, the thermometer measures the temperature when the water and the thermometer attains thermal equilibrium and this will mean a large amount of heat being lost from the little amount of water resulting in a very inaccurate reading.