### Boiling water in a paper cup

Other Relevant Demos :

Relevant Resource questions :

Concepts demonstrated

• Heat transfer by conduction

Diagram of apparatus

Equipment needed :

• paper cup (or paper folded into a box)
• bunsen burner
• matches
• tripod
• wire gauze
• water
• CCD camera (optional)
Method for setting up apparatus :

• Place a cup (or paper folded into a box) half filled with water on top of the wire gauze as shown with the bunsen burner underneath.
• Light the bunsen and heat the water in the cup.
Accessories (ie posters etc) :

Physics involved :

The heat produced by the bunsen burner is absorbed by the material on the wire gauze and is slowly transferred to the paper cup, hence heating the water. Because no flame strikes the cup and since the heating is slow the cup does not ignite.

It is the rate of transfer of the heat through the paper, rather than the boiling point fo the liquid, which causes the water to boil but does not cause the paper to burn.

How to use the Demonstration :

• Set up the apparatus and ask students what they think will happen.
• Perform the experiment demonstrating that the cup does not burn and that the water boils.
• Ask students to explain what they observe.
Everyday examples :

• Divers welding underwater
Things to do or add :

• Compare a wooden cup to a paper cup. Why do they differ?
• Use and oxy-torch instead of a bunsen burner. Again compare the results and explain any differences.