Metals can detect tiny temperature changes within their atoms through a process called thermal expansion. When a metal is heated, its atoms vibrate more rapidly and with greater energy. This increased energy causes the atoms to move apart slightly, which leads to an overall increase in the size of the metal. This change in size is known as thermal expansion.

The amount of thermal expansion that occurs in a metal depends on the metal’s composition and the temperature change that it undergoes. Different metals have different coefficients of thermal expansion, which describe how much a material will expand or contract for a given change in temperature. For example, steel has a coefficient of thermal expansion of approximately 12×10^-6 per degree Celsius, which means that for every degree Celsius increase in temperature, the steel will expand by 0.000012 times its original length.

This expansion and contraction of a metal due to changes in temperature can be used to detect small temperature changes within the metal. For example, in a thermocouple, a pair of different metals are joined together and used to measure temperature changes. When one end of the thermocouple is exposed to a change in temperature, it causes the metals to expand or contract differently, which generates a small voltage difference that can be measured and used to determine the temperature change.

Overall, the thermal expansion of metals is an important physical property that can be used to measure and detect small temperature changes within a material.