A metallic plate sticks firmly on the mouth of a water vessel made from another metal. By way of heating, one can detach the plate from the vessel. This is because heat expands

Thermal expansion is the tendency of matter to change its shape, area, and volume in response to a change in temperature. When a metallic plate is stuck on the mouth of a vessel made of a different metal, heating the assembly causes both components to expand. The detachment occurs because different materials possess different coefficients of linear thermal expansion (CTE). If the vessel is made of a metal with a higher CTE than the plate, it will expand more significantly for the same increase in temperature. This differential expansion increases the diameter of the vessel's mouth relative to the plate, thereby loosening the tight fit and allowing the plate to be detached. While both metals expand, the vessel expanding more than the plate is the physical mechanism that resolves the mechanical interference between the two parts.