The process of melting a crystalline solid can be
reversed if the liquid is cooled. The change from the liquid state
to the solid state is called freezing. <em><u>As the liquid cools, it loses
</u></em>
<em><u>thermal energy</u></em>. As a result, its particles slow down and come
closer together. Attractive forces begin to trap particles and the
crystals of a solid begin to form.
"The total kinetic energy of all the particles in a sample of
matter is called <em>thermal energy</em>. Thermal energy, an extensive
property, depends on the number of particles in a substance as
well as the amount of energy each particle has. <u>If either the
</u>
<u>number of particles or the amount of energy in each particle
</u>
<u>changes, the thermal energy of the sample changes</u>. With identically sized
samples, the warmer substance has a greater thermal energy."
