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Drops on a coin science experiment : Fizzics Education

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Drops on a coin

Drops on a coin

Follow FizzicsEd 150 Science Experiments:

You will need:

  • A coin
  • A pipette, eyedropper or a straw
  • Clear water
  • A mess bucket and cleaning materials

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Materials shown for experiment, Straw, Jar of water, Coin
1 Person with a straw trapping water out of a jar of water into a straw.

Place the straw in some water and then put your finger over the end. You can now remove the straw and keep the water inside (this works due to air pressure holding the water up). You could use a pipette to make this science activity easier too.

2 Water dropping out of a pipette onto a coin, one tiny drop of water

If you’re using the straw, carefully remove your finger to release your first drop of water.

3 Water dropping out of a pipette onto a coin, one big drop of water

Keep adding water drops, counting each one!

4 Water dropping out of a pipette onto a coin, multiple drops of water

If you look from the side, you should start to see the water begin to bulge over the side of the coin
We find a pipette easier for this part of the experiment.

5 Water dropping out of a pipette onto a coin, drops of water dropping off the coin

Keep going until the water spills over the side of the coin.

6 Primary school big science show
7 Teacher showing how to do an experiment outside to a group of kids.

Online courses for teachers & parents

– Help students learn how science really works

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What is happening?

The attractive forces between water molecules (called intermolecular forces) draw the molecules together. This happens in all liquids, where their molecules are more strongly attracted to each other than to the things around them. At the surface, the molecules are touching fewer other molecules, and so their attractive forces are stronger with the molecules they are touching, beside and below them. This holds the surface molecules together and holds the water in place over the coin, stopping water spillage for much longer than you would expect.

Because of surface tension, liquid surfaces act like a kind of ‘skin’, able to support small insects and materials on their surface.

Variables to test

More on variables here

  • Hot vs. cold water… does it make a difference?
  • What happens when the water has detergent in it?
  • Dirty vs. clean coins
  • Different size coins

Learn more!

Comments

8 thoughts on “Drops on a coin

    1. Wow! Its been a while since I’ve done this experiment. Can you find anything on the internet that describes why this is the case? Great job!

    1. Ha! Nah, I’m not a bot 🙂
      Can you get more drops than 10 on a $1 coin? I’ve got roughly 30 or so once. Let us know how you go!

  1. Hello Ben, just wanted to let you know that I am using your page for my chemistry assignment. My task is to create a 5-minute video completing an experiment related to chemistry. I chose your experiment as you explained it very well and you also made sure to demonstrate it very clearly. Thank you for your help, I’m going to be citing your work too! 🙂

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