Answer:
Thermal expansion is the tendency matter to change in shape, area, and volume in response to a change in temperature. Temperature is a monotonic function of the average molecular kinetic energy of a substance.
One of the most useful use of expansion by heat is for swiches onmany tyes of machinery and home appliancesThemostats in the millions of cars are poerated by using the eaxpansion of metal Themometers arre Bimetallic strips are used to trigger alarms or switch off heating. With heat one metal expands faster than the other which causes the strips to bend and break a circuit The disadvatages are just as common Railway lines need free movement d will buckle without sufficient clearance. Internal combustion engines need to be designed to allow for expansion contraction of metal parts It can be a nuisance for architects because when they build metal structures, they need to allow space for the metal to expand during hot weather.