The LabSheet-Linear-Thermal-Expansion TORRES.pdf document provided in the link you shared includes questions related to thermal expansion and contraction. The question you mentioned is not present in the document. However, to answer your question, a thermostat is a device that is used for regulating the temperature of a system and maintaining it at a desired level. It is commonly used in electrical heating and cooling devices such as air conditioners, refrigerators, and heaters. The thermostat measures the temperature of the system and automatically turns on or off the heating or cooling element to maintain the desired temperature. This helps to save energy and prevent overheating or overcooling of the system.