States of Matter - Class 5 Notes & Olympiad Questions

States of Matter

a) Matter refers to anything that has weight and takes up space. It is composed of extremely small particles that cannot be seen without the help of a microscope.
b) Matter comes in various forms found in nature, and we classify them into different categories based on their physical properties and the states they can exist in. These categories are known as states of matter.
c) There are mainly three states of matter: solid, liquid, and gas.

Different States of Water

a) Water is a unique substance because it can be found in three different forms: solid, liquid, and gas.
b) When water is in its solid state, it is called ice. In its liquid state, it is simply known as water. And when it turns into a gas, it is called water vapour.
c) The change from one state to another is influenced mainly by temperature and pressure. So, by adjusting these factors, water can transform from ice to liquid to vapour and vice versa.

Effect of Change of Temperature

1. Solid to Liquid (Melting)

a) When you heat a solid, like ice, it starts to melt and become a liquid.
b) The increase in temperature gives energy to the particles in the solid, causing them to move faster.
c) As the particles gain energy, they start to break free from their fixed positions and slide past each other, resulting in a change from a solid to a liquid state.

2. Liquid to Solid (Freezing)

a) When you cool a liquid, like water, it can turn into a solid, like ice.
b) As the temperature decreases, the particles lose energy and slow down.
c) Eventually, they come close together and arrange themselves in a more organized manner, forming a solid structure.

3. Liquid to Gas (Evaporation)

a) When you heat a liquid, such as water on a stove, it can change into a gas called water vapour.
b) As the temperature increases, the particles in the liquid gain energy and start moving faster.
c) Some particles gain enough energy to break free from the surface of the liquid and escape into the air, creating water vapour.

4. Gas to Liquid (Condensation)

a) When you cool down a gas, such as steam, it can turn back into a liquid.
b) As the temperature decreases, the particles lose energy and slow down.
c) They come closer together, and their attraction to each other becomes stronger, leading to the formation of liquid droplets.

Expansion and Contraction of Matter

a) When things get hotter, they expand because the particles they are made of start moving faster and need more space.
b) When things get colder, they contract because the particles slow down and come closer together, needing less space.

Expansion and Contraction of Water

a) Water is a bit different from most other substances. When it gets colder, like when you put it in the freezer, it contracts and takes up less space, just like other materials.
b) However, when water gets close to freezing and turns into ice, it expands instead of contracting. This means it takes up more space when it freezes.
c) When water freezes, the particles arrange themselves in a special pattern that needs more room. This is why ice cubes take up more space than the same amount of liquid water.
d) This expansion of water when it freezes is why you have to be careful when leaving a full water bottle in the freezer. If it freezes completely, the expanding ice can cause the bottle to crack or burst.
e) This expansion of water is also why ice floats on top of liquid water. The expanded ice is less dense than the liquid water, so it stays on the surface.

Classification of Changes in Matter

Changes in the form of matter can be categorised as physical changes or chemical changes.

Physical Change

a) A physical change is when the appearance of matter changes, but no new substances are formed.
b) It doesn't change the amount of matter; it can be divided into parts or separated.
c) During a physical change, no new type of matter is created.
d) Most physical changes are reversible, meaning they can be undone.
e) Examples of physical changes include:

Melting ice: Solid ice turns into liquid water when heated, and this can be reversed by freezing the liquid water back into solid ice.

Inflating a balloon: When we fill a balloon with air, its shape changes, but we can let the air out, and it returns to its original shape.

Sharpening a pencil: The physical appearance of the pencil changes when it is sharpened.

Cutting an apple into slices: The shape of the apple changes, but the amount of matter remains the same. It is just divided into parts.

Chemical Change

a) A chemical change is when new substances with different properties are formed.
b) These changes involve a change in the amount of matter.
c) Some new type of matter is created, which looks entirely different from the original matter.
d) Chemical changes are generally irreversible, meaning they cannot be reversed back to their original form.
e) Examples of chemical changes include:

Burning paper: The paper turns into ash, which cannot be changed back into paper.

Rusting of iron: Iron reacts with oxygen in the air and forms a new substance, rust, which is different from the original iron.

Burning a candle: The candle reduces in size and turns into wax, which cannot be changed back into the original candle.

Cooking eggs: The chemical composition of the eggs change when they are heated, and the cooked eggs cannot be turned back into uncooked eggs.