What are the three states of matter?
The three common states of matter are solid, liquid and gas. A fourth state, plasma, is less familiar on Earth but is the most common in the universe.
In a solid, particles are packed tightly in fixed positions and only vibrate, so solids keep their shape. In a liquid, particles are close together but can slide past each other, so liquids flow and take the shape of their container while keeping the same volume. In a gas, particles move fast and far apart, filling any space.
Matter changes state when energy is added or removed. Heating ice makes it melt into water, and further heating makes the water evaporate into steam. Cooling reverses the process through condensation and freezing. Some substances, like dry ice, turn straight from solid to gas, a change called sublimation.
Plasma and beyond
Plasma is a hot gas in which electrons have been stripped from atoms, making it electrically charged. Stars, lightning and neon signs contain plasma. Scientists have also created exotic states in labs, such as Bose-Einstein condensates, formed when atoms are cooled to almost absolute zero.
Did You Know?
Water is unusual because its solid form, ice, is less dense than its liquid form. That is why ice floats and lakes freeze from the top down.