Solids, liquids and gases are the three main or fundamental phases of matter. Each has a different density and a different level of stability. What determines the stability of each phase is the bond between its atoms. The tighter the bond between its atoms, the more stable that phase of matter is. Solids are the most stable form of matter, followed by liquids and then gases. Solids have a defined shape and do not take the shape of their container. Liquids do not have a defined shape and take the shape of their container, the same goes for gases. Once again it is the bond between the atoms of liquids and gases that ensures that it does not have a defined shape. The first phase of matter is solids. Solids are the most stable form of matter. Solids are more stable than liquids and gases. One type of solid is a crystalline solid. Particles in a crystalline solid have a regular repeating pattern. The types of crystalline solids are metals, alloys, salts, valence crystals, molecular crystals, polymers, and plastics. Most elements crystallize as metals. Some solids can also be frozen liquids. The atoms in a solid are tightly bonded, meaning it has a definite shape. The second phase of matter is liquids. Liquids do not have a defined shape. Liquids are less ordered than solids but more ordered than gases. Liquids can flow very easily. Liquids also take the shape of their container. Most liquids are excellent conductors. Most liquids are also good solvents. Some solids float in liquids depending on their density. If the solid is less dense than the liquid then it floats on the surface of the liquid. If the solid is denser than the liquid then it sinks into the liquids. For example, an egg normally sinks in water because its density is higher than that of water. When you add salt to water, the density of the water becomes higher than the density of the egg, so the egg floats. The third and final fundamental phase of matter is gas. Gases are the least ordered of the three phases of matter. Gases take the shape of their container due to the very weak bond between their atoms. Gases also have a very low density. The average gas is 1000 times smaller than the average liquid. The volume of gas varies with many factors, including temperature and pressure. These are explained in Charles and Boyle's laws. Boyle's law states that the volume of gas varies indefinitely with the pressure applied to it.