The particles in a substance slow down when the average kinetic energy of the particles decreases. As the average kinetic energy decreases, the internal energy decreases, and so the thermal energy decreases. As the thermal energy of the substance decreases, the temperature decreases.
Lead is a chemical element with the symbol Pb (from the Latin plumbum) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point.
