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๐ฌ Think about it
Stir sand into water and the sand stays visible, floating about, never dissolving. Muddy water is the same. How do we clear such cloudy water? Let us meet suspensions and two ways to clean them.
What is a suspension?
- It is a heterogeneous mixture where solid particles do not dissolve.
- The particles stay suspended throughout the liquid.
- They are larger than solution particles and visible to the naked eye.
Example:
Sand in water, sawdust in water and tea leaves in water are suspensions.
What is centrifugation?
- It spins a mixture in a tube at high speed.
- The centrifugal force pushes heavier particles outward.
- Heavier particles settle at the bottom; lighter liquid stays on top.
- It is used to separate blood components and in industries.
In this Activity, we will build a simple hand-spun centrifuge to see heavier particles move outward.
Procedure
Make your own centrifuge with a cardboard disc and thick thread. Spin it and watch how the heavier particles move outwards. Decide which mixture you would like to separate with this mini centrifuge.
โ Summary
- Make a cardboard centrifuge.
- Spin it fast.
- Heavier particles move out.
- See separation by spinning.
What is coagulation?
- It adds a substance that makes fine particles clump together.
- The added substance is called a coagulant, such as alum.
- The larger clumps settle by gravity (sedimentation).
- They can then be removed by decantation or filtration.
Example:
Making paneer from milk uses lemon juice or vinegar as a coagulant to clump the milk proteins.
Important Points
- A suspension has visible, undissolved particles that stay spread out.
- Centrifugation spins a mixture so heavier particles settle.
- Coagulation uses a coagulant to clump fine particles so they settle.
๐งฉ Threads of Curiosity
- The spinning game is a folk dance.
- It is called phugadi in Marathi and kikli in Punjabi.
- The outward pull you feel while spinning is like the force in centrifugation.
๐ Bridging Science and Society
- A paperfuge is a simple hand-powered device that works like a centrifuge.
- It spins blood samples at very high speed without electricity.
- It separates heavier components from lighter ones.
- This low-cost tool helps detect malaria and anaemia in remote areas.
โ Test Yourself
-
What is a suspension?
View Answer
A heterogeneous mixture with visible, undissolved particles spread through the liquid. -
How does centrifugation separate a mixture?
View Answer
Fast spinning pushes heavier particles to the bottom of the tube. -
What does a coagulant do?
View Answer
It makes fine suspended particles clump together so they settle.
Important Definitions
- Suspension — a heterogeneous mixture with undissolved particles spread through the medium.
- Centrifugation — spinning a mixture at high speed to separate heavier particles.
- Coagulation — adding a coagulant to clump fine particles so they settle.
๐ NCERT Question 7 — How would you separate
How would you separate mixtures like mud from water, plasma from blood, and oil from water (Table 5.3)?
View Answer →
