CHANGE OF STATE
Matter can move from one state to another, but can still be the same substance. A change of state, also called a phase change, is a physical change from one state of matter to another, for example, from solid to liquid or from liquid to gas
How does matter move from one phase to another?
If the motion of the atoms is altered by pressure or temperature, the state can change too. By lowering the temperature of water, it can freeze into a solid. By heating water, it can become steam which is a gas. Whether solid, liquid or gas ‐ water is still water.
Pressure can change matter from one state to another. Deep in the earth solids turn to liquids because the heavy weight of layers and layers of the earth push down on the solids causing them to turn to liquid magma. This is just one example of how pressure can change matter too.
Other matter changes too, but often only exists in two states or requires the help of humans and technology to move through all three phases. Water is the only matter on earth that can be found naturally in all three – solid, liquid and a gas.
There are six distinct changes of state which happens to different substances at different temperatures. The six changes are:
- Freezing: the substance changes from a liquid to a solid. For example, the change of water to ice when temperature is lowered is called freezing. In other example, Lava is liquid rock, which erupts through a volcano at temperatures as high as 1,500ºC through a volcano. However, the red-hot lava cools as it meets the Earth’s surface, and turns back into solid rock again. This change from liquid to solid is what is referred to as freezing or solidifying.
- Melting: the substance changes back from the solid to the liquid. When a solid is heated, the particles are given more energy and start to vibrate faster. At a certain temperature, the particles vibrate so much that their ordered structure breaks down. At this point the solid melts into liquid. The temperature at which this change from solid to liquid happens is called the melting point. Each solid has a set melting point at normal air pressure. At lower air pressure, such as up a mountain, the melting point lowers.
- Condensation: the substance changes from a gas to a liquid. Dewdrops are often found on a spider’s web early in the morning after a cold night. Water that is present as a gas in the air cools down and changes into tiny drops of liquid water on leaves and windows. This change from gas to liquid is called condensation.
- Vaporization: the substance changes from a liquid to a gas. Even without boiling water in a kettle, some of the liquid water changes to gas. This is evaporation. It occurs when a liquid turns into a gas far below its boiling point. There are always some particles in a liquid that have enough energy to break free from the rest to become a gas.
- Sublimation: the substance changes directly from a solid to a gas without going through the liquid phase. An example of sublimation happens when dry ice turns directly into gas. Gas can also change into a plasma. In order to do this, you have to add an enormous amount of energy to the gas in order to free up the electrons from the atoms.
- Deposition: the substance changes directly from a gas to a solid without going through the liquid phase. Deposition is one you may not know, but this happens when water vapor goes directly to freezing, like when there is frost on a cold winter morning.