Solids
Solids are usually hard, because their molecules have been packed
together. Solids can be hard, soft, big or small like
grains of sand. solids hold their shapes and don't flow like a
liquid or spread out like a gas. Instead,
they keep their definite form. A rock will always look like a
rock unless something occurs to change
it. Most rocks are mixtures of many different compounds. Concrete is a good example
of a man-made mixture. Solids are formed when the attractive forces between individual molecules are greater than the energy causing them to move apart. Individual molecules are locked in position near each other, and cannot move past one another. For example if you cool water to past 32 degrees Fahrenheit
water will freeze.