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Minor Versionm

by Procheta Mallik


In a 1 litre plastic bottle, kept horizontal, make a hole in the middle and mount a sketch pen and seal it watertight. Poke a spoke in the middle of the sketch pen, allowing the bottle to rotate on the horizontal axis. Put any liquid in the bottle and spin the bottle and see it move towards the ends of the bottle. With a mixture of two or more immiscible liquids, one should be able to see them separate

    • Use the lit candle under adult supervision

    • Be careful with the hot piece of metal wire

    • Handle the scissors with care

  1. Take an empty plastic bottle and make a hole at the halfway mark using a candle-heated piece of metal wire .
    • Take an empty plastic bottle and make a hole at the halfway mark using a candle-heated piece of metal wire .

    • Enlarge the hole using scissors so that the straw can fit through the hole.

    • Repeat the above two steps for the diametrically opposite side of the bottle.

    • Cut the straight straw in half .

    • Insert the straw inside the holes and glue the straw in place at both holes

    • Using heated wire make a hole at the centre of the bottle cap.

    • Fill the inside of the bottle cap with foam or newspaper.

    • Insert the small cycle spoke through the bottle cap filled with foam/newspaper all the way through.

    • Then insert the cycle spoke through the straw glued to the bottle.

    • Now screw the spoke nut on to the spoke to secure it in place

    • Take 100 ml of coloured water and pour it into the plastic bottle .

    • By holding the screw end of the cycle spoke, give a push to one side of the bottle so that it spins.

    • Do not hold the spoke nut itself while spinning, as that might then come undone!

    • You should see the coloured water getting pushed to either side in exactly equal amounts

    • Try the same with a mixture of oil and water.

    • Make sure the holes made on the bottle are not too much bigger than the straw .

    • Straws should be glued watertight, else water will leak each time you play with the centrifuge

    • You must give a sufficient push to spin the bottle fast enough and see the two halves visibly divide equally

    • What happens when you mix solid-liquid, e.g. muddy water, and have it spin in the centrifuge?

    • Why does the liquid divide equally in both halves?

    • What would happen if our axis was not right at the centre of the bottle?

    • Where is our daily lives or in the industry are centrifuges used?

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