How many coins to sink a boat? – STEM Challenge

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Today’s STEM Challenge is super simple. The aim is to find out how many coins it takes to sink a foil boat.

First we cleaned up our treasure, then we made different sized tinfoil boats and tried to sink them!

If you want to take the pirate theme further, we love making treasure maps with cold tea and coffee too!

How to clean coins

To clean your coins, just put them in vinegar for a couple of hours and they’ll soon be super shiny! If you want to turn this into more of an investigation there are a few other coin cleaning methods you could try.

  • Scrub the coins with a baking soda paste ( make this by mixing a little water with baking soda )
  • Soak in lemon Juice
  • Soak in a fizzy drink – don’t drink the fizzy drink afterwards!
How to clean coins

Sink the Boats

You’ll need

Tin foil



Construct a boat with tinfoil.

Check the boat floats.

Once you’re happy the boat floats add coins slowly to find out how many coins it takes to make it sink.

Try spreading the coins out for the first attempt and then try again but place all the coins at one end.

tinfoil boat
foil boat

Remember to make sure the coins are dried for each boat you test.

Boat STEM Challenge Extension Tasks

Repeat the investigation, but this time use different sized foil boats. Do smaller boats sink with less coins?

Make boats from recycled materials and work out how much weight it takes to make each one sink.

boats made from recycled material and lemon skin

What makes an object float?

Things float if they are less dense than the liquid they are in ( in this case water ). If they are more dense they sink.

Adding coins to the boats increased the density and when the density became greater than that of water the boat sank.

More STEM Challenges for Kids

We’ve got printable STEM Challenge cards containing 12 fun and super simple STEM challenges for kids, including building rafts, super long paper chains and fizzy potions.

STEM Challenge cards

Our newspaper STEM Challenges are great fun too! Make dens, shoes and even famous landmarks using just newspaper and tape!

The post How many coins to sink a boat? – STEM Challenge appeared first on Science Experiments for Kids.

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