You have to note that pure substances can be elements or compounds. There is only one component all throughout. On the other hand, a mixture is a combination of different elements and compounds. They can appear in different phases. For example, air is a mixture. It is composed of pure substances of oxygen, carbon dioxide, and nitrogen.
<span>When a
substance is heated, its atoms gain
energy and begin to vibrate rapidly within the lattice
of the substance (the substance expands). As more heating continues, the atoms
gain even more energy and move more rapidly until they are able to overcome the
force of the bonds, that hold the atoms together
in the lattice, until the structure is disrupted. </span>
