Our Earth is continuously changing due to natural processes. Two important processes are weathering and erosion. These processes help in the formation of soil and continuously reshape the Earth's surface.
Weathering:
Weathering is the breaking down of rocks into smaller pieces at the same place due to natural agents.
Natural Agents of Weathering:
- Wind
- Rain
- Temperature changes (heating and cooling)
- Plant roots
- Flowing water
Key Features:
- Rocks break into smaller pieces.
- The broken pieces remain where they are formed.
- No transportation of rock particles takes place.
- It is mainly a physical change because no new substance is formed.
Example:
Cracks developing in mountain rocks.
Plant roots splitting rocks.
Rocks breaking due to repeated heating and cooling.
Erosion:
Difference Between Weathering and Erosion:
Erosion is the transportation of weathered rock particles from one place to another by natural agents.
Agents of Erosion:
- Flowing water
- Wind
- Glaciers
- Sea waves
Key Features:
- Moves rock particles from one place to another.
- Usually occurs after weathering.
- Changes the shape of the Earth's surface.
- Helps in forming valleys, riverbanks, beaches, and sand dunes.
Example:
Rivers carrying soil after heavy rainfall.
Wind carrying sand in deserts.
Sea waves transporting sand along the coast.
| Weathering | Erosion |
|---|---|
| Breaks rocks into smaller pieces. | Carries the broken rock particles. |
| Rocks remain in the same place. | Rock particles move to another place. |
| No transportation occurs. | Transportation always occurs. |
| First step in soil formation. | Helps in the movement of soil and sediments. |
Soil Formation:
Soil forms over a long period through the combined action of weathering and erosion.
Steps in Soil Formation:
- Large rocks develop cracks.
- Weathering breaks rocks into smaller particles.
- Erosion transports some of these particles.
- The particles mix with humus, air, and water.
- Fertile soil is formed.
Importance of Soil:
- Supports plant growth.
- Provides habitat for many organisms.
- Stores water and nutrients.
- Essential for agriculture.
Physical and Chemical Changes:
Every change around us can be classified as either a physical change or a chemical change.
| Characteristics | Physical Change | Chemical Changes |
| Definition | A physical change is a change in which only the physical properties (shape, size, or state) of a substance change, and no new substance is formed. | A chemical change is a change in which one or more new substances are formed with different properties. |
| Characteristics |
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| Examples |
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Why is Burning of a Candle Both a Physical and a Chemical Change?
A burning candle is one of the best examples where both physical and chemical changes occur simultaneously.
Physical Change:
- The solid wax melts into liquid wax.
- The melted wax solidifies again on cooling.
- No new substance is formed.
Chemical Change:
- The wax vapour burns in the presence of oxygen.
- It forms carbon dioxide and water vapour.
- Heat and light are released.
- New substances are formed.