# Properties of Matter and Composition of Air - Grade 6 Science

## Properties of Matter - Expansion and Contraction

### Expansion And Contraction In Liquids

- When a water in a bottle is heated, its volume increases. The increase in volume due to heating is called expansion.
- When the water cools, its volume decreases. This decrease in volume due to cooling is called contraction.

### Expansion And Contraction Of Gases

Observation
The balloon is inflated when the bottle is placed in hot water, and deflates when the bottle is placed in cold water.
- Air expands on heating and contracts on cooling.

### Expansion And Contraction In Solids

Observation
Before heating, the cold metallic ball easily goes through the ring. Once heated, the now hot metallic ball does not go through the ring.
- Solid expands when heated and contracts when cooled.

### Application Of Expansion And Contraction

(i) It is used in thermometers.
- The liquid inside the thermometer expands when heated and contracts when cooled.

(ii) Electric power lines are loosely fixed during construction.
- This allows the space for expansion and contraction during hot and cold seasons.

(iii) The road engineers use the principle of expansion and contraction when making bridges.
- One end of the bridge is given some space for expansion and contraction during hot and cold seasons.

(iv) The railway lines are left with spaces between the metal rails.
- This allows enough space for expansion and contraction.

## Composition of Air

- Air is a mixture of gases.
- The major gases that are found in the air are:
• Nitrogen - 785%
• Oxygen - 21%
• Carbon dioxide - 0.03%
• Inert gases - 0.97%

### Uses of oxygen

- Oxygen is used in burning.
- Oxygen is used in germination.
- Oxygen is used in breathing.

### Uses of carbon dioxide

#### 1. Photosynthesis.

-This is the process by which green plants make their own food.
- Green plants use carbon dioxide to make food during the day and release oxygen to the atmosphere.
- Therefore, they clean air.

#### 2. Preservation of soft drinks

- Carbon dioxide is added in soft drinks to preserve them.
- Therefore they can last for longer time.

#### 3. Making fire extinguishers

- Carbon dioxide does not support burning.
Therefore, it is used to put out fire.

### Uses of nitrogen

#### 1. In leguminous plants

- Leguminous plants such as beans, peas and clovers use nitrogen from air in the soil to make proteins.

#### 2. In food preservation/packaging

- Nitrogen is used in food packaging containers to keep off oxygen in order to make the food last longer.

#### 3. In light bulbs

- To prevent the filament from burning.

#### 4. In making fertilisers

- Nitrogen is one of the materials used in making fertilisers that are used by plants.

### Uses of inert gases

1. Making electric tubes and bulbs.

### Explore More Grade 6 Science and Technology Topics

#### User Reviews: Share Your Feedback!

Your review has been successfully submitted.
Tell us what you think about the notes.

Submit Comment

### Here's what our users had to say ...

Guest User
They are helpful to me they have made me improve my results