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Boiling Water with Ice
You will need:
- A clear glass flat bottomed flask with a bung
- A hot plate or cooker top
- Some water
- Some ice
- Some heat proof gloves and a heat proof mat
- A ring stand or other way of supporting the flask upside down
What to do:
- Bring some water to boil in the flask.
- Remove the flask from the heat, and immediately put the bung tightly in.
- Leave the flask for a minute, then suspend it upside down on the ring stand.
- Place some ice cubes on the flat bottom of the flask. What happens?
- You should see the water starting to boil again!
- As the water and water vapour in the flask cools because of the ice, the pressure in the flask falls. Water boils at lower temperatures at lower pressures!
- This is why it is not possible to make a good cup of tea at high altitudes where the pressure is lower! The boiling point of water is 100°C at standard pressure. On top of Mount Everest the pressure is about 26.39 kPa and so the boiling point of water is 69°C.
Find out more:
See this experiment
Find out more about pressure and boiling here
Find out more about pressure and winds in the atmosphere here (select
'atmosphere' and then 'pressure')