I read this background article the other day: A thermometer is a device used to measure temperature. It is placed in contact with an object and allowed to reach thermal equilibrium with the object (they will have the same temperature). The operation of a thermometer is based on some property, such as volume, that varies with temperature. The most common thermometers contain liquid mercury, or some other liquid, inside a sealed glass tube. The liquid expands and contracts faster than the glass tube. Therefore, when the temperature of the thermometer increases, the liquid volume expands faster than the glass volume, allowing the liquid to rise in the tube. The positions of the liquid in the tube can then be calibrated for accurate temperature readings. Other properties that change with temperature can also be used to make thermometers; liquid crystal colors and electrical conductivity change with temperature, and are also relatively common thermometers. I am facing a new situation today: A group of middle school students is measuring the temperature of various liquids for a chemistry lab using a mercury thermometer. They have a beaker of boiling water, a beaker of ice water, and a beaker of water at room temperature. Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: If the students move the thermometer from one beaker to another and the mercury levels fall, is the temperature higher or lower?
Answer:
lower