Introduction
In daily life, we often find mixtures of different substances. Sometimes these mixtures contain useful substances mixed with unwanted materials. The process of separating different components of a mixture is called separation of substances.
Why Do We Separate Substances?
- To remove impurities
- To obtain useful substances
- To make substances safe and suitable for use
Methods of Separation
1. Handpicking
- Used when unwanted substances are large and visible.
- Example: Removing stones from rice.
2. Threshing
- Used to separate grains from stalks.
- Done by beating or using machines.
3. Winnowing
- Used to separate lighter husk from heavier grains using wind.
- Example: Separating chaff from wheat.
4. Sieving
- Used when particles are of different sizes.
- Example: Separating bran from flour.
5. Sedimentation
- Heavy particles settle at the bottom of water.
- Example: Mud settling in water.
6. Decantation
- Clear liquid is poured out after sedimentation.
- Used to separate solid from liquid.
7. Filtration
- Used to separate insoluble solids from liquids.
- Example: Filtering tea leaves from tea.
8. Evaporation
- Used to separate dissolved solids from liquids.
- Example: Obtaining salt from seawater.
9. Condensation
- Conversion of water vapour into liquid.
- Used with evaporation to get pure liquid.
Soluble and Insoluble Substances
- Soluble substances dissolve in water (salt, sugar).
- Insoluble substances do not dissolve (sand, chalk).
Saturated Solution
A solution that cannot dissolve more solute at a given temperature is called a saturated solution.
Important Questions (Short Answers)
1. What is separation of substances?
Process of separating different components of a mixture.
2. Why do we separate substances?
To remove impurities and obtain useful substances.
3. What is handpicking?
Separating large unwanted particles by hand.
4. Give one example of handpicking.
Removing stones from rice.
5. What is threshing?
Separating grains from stalks.
6. What is winnowing?
Separating lighter husk from heavier grains using wind.
7. Give one example of winnowing.
Separating chaff from wheat.
8. What is sieving?
Separating particles of different sizes using a sieve.
9. Give one example of sieving.
Separating flour from bran.
10. What is sedimentation?
Heavy particles settle at the bottom of water.
11. What is decantation?
Pouring out the clear liquid after sedimentation.
12. Give one example of decantation.
Separating water from muddy water.
13. What is filtration?
Separating insoluble solids from liquids using a filter.
14. Give one example of filtration.
Filtering tea leaves from tea.
15. What is evaporation?
Separating dissolved solids from liquids by heating.
16. Give one example of evaporation.
Getting salt from seawater.
17. What is condensation?
Conversion of water vapour into liquid.
18. What are soluble substances?
Substances that dissolve in water (e.g., sugar, salt).
19. What are insoluble substances?
Substances that do not dissolve in water (e.g., sand, chalk).
20. What is a saturated solution?
A solution that cannot dissolve more solute at a given temperature.