Question

True/False: Because hot water cools down faster than cold water, an ice cube tray filled with hot water will freeze faster than an ice cube tray filled with cold water. Explain your choice.

Hint: Although hot water cools down at a faster rate than cold water, it also has to undergo a larger temperature change. As it cools down, what happens to the rate at which it continues to cool down?

Explain how a mercury thermometer works. A mercury thermometer breaks open and loses its mercury while the thermometer is at a temperature of 20°C. You refill the thermometer with colored ethanol to a level of 20°C. a. At a temperature of 10°C, will the thermometer read a value below, above, or exactly 10°C? Explain. b. At a temperature of 30°C, will the thermometer read a value below, above, or exactly 30°C? Explain.

Answer 1

Hello!

Answer : TRUE!

It is true that hot water cools down much faster than cold water. And so the ice cube trays filled with hot water cool down more quicker than cold water poured into the tray!

This is because the rate at which heat is lost from a liquid at higher temperature is higher (latent heat) and cools down. But as more heat is lost due to convection and conduction, the rate of change of temperature slows down. This is because there is no heat left to radiate and more energy has to be spent on making it even more cold.

Working of mercury thermometer

It is also called as maximum thermometer. It has a constriction at the neck of the bulb whch holds the mercury! As the temperature rises the forces of expansion push mercury up the cappiliary tube to indicate the temperature.

If the thermometer is broken, then there will be no pressure inside the mercury tube to force mercury up the graduations and it cannot work. Alcohol on the other hand has a tendency to evaporate easily. So if the temperature increases beyond the boiling point of ethanol, then it evaporates and cannot indicate a reading.