Explanation and experiment approaches are the best ways to teach properties of solids. A solid material, in its physical state, has a fixed shape. It is hard and the shape cannot be changed easily. It exhibits a regular arrangement of molecular particles and is rigid. Many of them have a definite three-dimensional shape with surfaces at specific angles to each other, like table salt (sodium chloride) at the room temperature. Table salt crystals have cubic shape with faces at 90°.
The size or shape of solids do not change at a given temperature. However, they can be resized or reshaped under certain conditions and temperature. A piece of iron has a shape and size that does not change at room temperature. Other example like ice, another solid, is solid at a temperature below 0°C (32°F).
When the crystals in a solid form are arranged and packed tightly, they are held together. There is little motion of the particles, and therefore, vibrate only very slightly. In addition, solids do not flow as liquids and gases do. For instance, when a solid is placed into a container, it cannot completely fill up the container. Instead, there will be spaces in between the solid and the container.
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