States Of Matter - Science Lessons for Grade 6 Students

What is matter? Matter is any physical substance in the universe that takes up space and has mass. An apple, a person, a table, air, Water, and ice are all physical substances, and hence they are all matter.

Matter can be in different states. For example, an apple is in solid state, but apple juice is in liquid state. Simply speaking, there are three states of matter: solid, liquid and gas.

Can you arrange the different substances or matter given below into solid, liquid and gas?

Orange juice | comb | oxygen | steam | book | water | ice | car | nitrogen | paper

Matter in solid state

Matter in solid state has a fixed volume and shape. For example, a stone, which is matter in solid state, has a fixed volume and shape. Solids stay in one place unless it is moved by an outside force. You might think that since sugar, salt and flour can all be poured from one container to another container, they are not solids. But they are still solids, because each particle of salt or sugar keeps the same volume and shape. Other examples of solids include ice, sand and wood.

In a solid, the particles that make up the solid are all closely packed together. In other words, the force of attraction between the particles in solids is very strong. The particles cannot move freely. Because of this a solid has a fixed volume and shape. Solids can change their shape and volume only if an outside force cuts it or breaks it.

Matter in liquid state

Matter in the liquid state has the shape of its container, even though it has a fixed volume. For example, if lime juice is poured into a glass jar it has the shape of the glass jar. If it is poured into a test tube, it has the shape of the test tube. Liquids cannot be held easily, but they can flow easily. Examples of liquids include water, milk and honey.

In a liquid state the particles that make up the liquid are less tightly packed compared to solids. So they have more freedom of movement. In other words, the force of attraction between the particles in the liquid are less than that of solids.

Matter in gaseous state

Matter in gaseous state has variable shape and volume. They can spread out and change their shape and volume according to the container in which they are. Oxygen in an oxygen tank has the volume and shape of the oxygen tank. Many gases are invisible, and they can be squashed.

In gases, the particles that make up the gas are far apart from each other. They are free to move around. In other words, the force of attraction between the particles in a gas is very little.

Matter can be changed from one state to another by heating it or cooling it. Let us look at the different ways in which matter can change between the three states.

Changes between the three states

Melting

Melting is a process by which a solid changes into liquid. It happens when the solid is heated. The temperature at which a solid changes into liquid is termed its melting point.

Freezing

The process by which a liquid turns into a solid is termed freezing. Most liquids undergo freezing when the temperature is made sufficiently cold. For example, water becomes ice at around 0°C.

Evaporation

Evaporation is the process by which a liquid becomes gas. This usually happens when the liquid is heated up. For example, water evaporates at its boiling point (212° F, 100° C)

Condensation

Condensation is the opposite of evaporation. It is the process of a gas changing to liquid. Have you seen dew on leaves early in the morning? Dew is formed when the warmer air condenses on the cool leaves early in the morning.

Deposition

Deposition is the term for the transformation of gas into solid without passing through the liquid phase. For example, in sub-freezing air, water vapour turns into ice without first becoming a liquid. This is how frost forms on the ground, on leaves, or other surfaces.

Sublimation

Sublimation is the change of solids directly to gases. This happens when solids absorb enough energy to overcome the forces of attraction between them. For example, dry ice can change into gas under the right temperature and pressure conditions.