Spin it fast
Centrifugation.
Swinging a bucket
Two children hold hands and spin fast, as in the folk game phugadi (Marathi) or kikli (Punjabi). They feel pulled outward.
A tube of a mixture is spun the same way. Where do the heavier particles go?
What this lesson covers
The idea
Centrifugation spins a mixture in a tube at high speed; the centrifugal force, the outward force on a body in circular motion, drives heavier particles outward to the bottom of the tube while the lighter liquid stays at the top.
Swinging a bucket
Two children hold hands and spin fast, as in the folk game phugadi (Marathi) or kikli (Punjabi). They feel pulled outward.
A tube of a mixture is spun the same way. Where do the heavier particles go?
- Outward, to the bottom of the tube
- Inward, to the top
- They do not move
Spin the blood sample
Start the centrifuge, add minutes of spinning, then stop it.
Centrifugation
Centrifugation spins a mixture in a tube at high speed. The tubes become horizontal, and the centrifugal force (the outward force on a body moving in a circle) pushes the heavier particles outward, where they settle at the bottom of the tube. The lighter liquid remains at the top.
It is widely used in laboratories to separate blood into red blood cells and plasma, and in many chemical industries.
Paperfuge. A hand-powered device based on a common toy can spin blood samples very fast without electricity. This low-cost tool helps detect diseases such as malaria and anaemia in remote areas.
Notes
Centrifugation: fast spinning pushes the heavier particles outward to the bottom of the tube; the lighter liquid stays on top.
Check yourself
In a centrifuge, which particles move outward to the bottom of the tube?
Centrifugal force acts…
Which job is centrifugation used for?
Where would a paperfuge be most useful?
- The lighter liquid. The lighter liquid stays on top.
- Air bubbles only. Not what is described.
- The heavier particles — correct. Yes.
- toward the centre. That is the opposite direction.
- outward, on a body moving in a circle — correct. Yes.
- upward only. It is an outward force.
- Making sugar crystals from syrup. That is crystallization.
- Separating camphor from sand. That uses sublimation.
- Separating blood into red blood cells and plasma — correct. Yes.
- In remote areas without electricity, to help detect malaria and anaemia — correct. Yes.
- Inside a rocket. Not its use.
- Where only electric machines are allowed. A paperfuge works without electricity.