Our universe is formed of matter. Matter can be obtained in different states. The predominant states of matter are solid, liquid, and gas. The states of matter do not change unless there is a change in temperature or pressure. The change in the state of matter is used in many practical applications like purification, separation of compounds, etc. In this article, we look at 6 processes for changing states of matter.
Three states of matter
- Solid – The particles in a solid are closely packed to each other. The motion of the particles is very restricted. Solids do not flow and have a definite shape.
- Liquid- Liquids do not have a definite shape. The shape depends on the shape of the container as liquids can flow.
- Gas – Gases occupy the entire container and have no defined shape.
Apart from these three states of matter, there are other less-known states like plasma, Bose-Einstein condensate, excitonic, degenerate matter, photonic matter, etc
What do you mean by changing states of matter?
Changing states of matter is a physical change in matter. It is a reversible change and does not involve any chemical change. That means the chemical constituents of the material will remain the same but the physical state of the matter will change. For example, water will be H2O even while it is ice, liquid water, or water vapor.
How does matter change states?
Depending upon temperature and pressure matter can change state. The specific temperature at which the change happens from solid to liquid is called the melting point. The temperature for transformation from liquid to gas is defined as the boiling point. The change also happens in the opposite direction from gases to liquids and liquids to solids. The melting points and the boiling points can be controlled by varying the pressure. When matter loses or absorbs energy there is a change in the state of matter. We observe changing states of the matter daily at our home itself like the melting of an ice cube. When we take an ice cube out of the refrigerator it turns into liquid. And while boiling, the water turns into vapor.
Examples of changing states of matter
- When water (liquid) is poured into a mold or ice tray and is placed in a freezer for some time, it turns into solid ice.
- If we keep our ice cream out in the open for some time, it starts melting. It turns from solid to liquid.
- Essential oils give out a smell by evaporating into a gaseous form.
- Liquified natural gas(LPG) is an example of converting gases into liquids.
The 6 changes of state
The above image clearly shows the processes involving changes in the state of matter.
- Melting – change from solid to liquid
- Freezing – change from liquid to solid
- Evaporation – change from liquid to gas
- Condensation – change from gas to liquid
- Sublimation – change from solid to gas
- Reverse sublimation(or deposition) – change from gas to solid
Let us look at one of the processes in detail:
MELTING : | Melting is the process of changing a solid into a liquid. The atoms in a solid stick closely together. When we heat a solid to a certain temperature then it turns into a liquid. So, when the temperature increases, the atoms gain energy and they start moving instead of vibrating in a fixed position. And since the atoms start to move the solid turns into a liquid. For example, in order to give shape to metal, it is heated to very high temperatures to turn into a liquid state. |
FREEZING:  | Freezing is the process of changing a liquid into a solid state. Energy is absorbed from the material such that the freedom of the atoms is restricted. For example, when water becomes cool(drops in temperature) it turns into ice(solid state). |
EVAPORATION: | Evaporation is the process of changing liquid into vapor form. When a liquid is heated, the molecules present at the surface absorb energy and escape into the atmosphere as a gas. For example, if you heat water for a long time, then it will get disappeared as steam. |
CONDENSATION:  | Condensation is the process of changing a gas into a liquid state. A gas when it is cooled down, losses energy. Hence, the particles can no longer fly. The particles then clump together and form a liquid. For example, fogging of the mirror after a hot shower or the formation of fog in the air. |
| SUBLIMATION: | Sublimation is the process of converting solid matter into a gas directly. Sometimes some chemicals skip the liquid state and turn directly into gas. It happens only under special conditions. For example, the naphthalene balls used in our home directly sublime into the air and disappear. |
| DEPOSITION (OR REVERSE SUBLIMATION): | The deposition of gases is the reverse of sublimation. Here, the gases are directly converted into solids. You might have noticed the deposition of ashes in a chimney due to the gases. |
