Fire Proof Paper

This activity encourages practical enquiry skills in the area of 'Energy, electricity and forces'.

Year groups: 7-9 (ages 11-14)

Educational objective

To see how effective water is at conducting heat away from a paper cup.

Key learning

Paper will burn only when it reaches the required temperature (233 °C).
Water conducts heat much more effectively than paper.
As the water effectively transfers the heat away from the cup it can be made to boil without the paper cup getting hot enough to burn.

Materials needed, per student

Candle
Tripod
Pipe clay triangle
Paper cup
Water
Teaspoon of hot chocolate powder (optional)

Practicalities

It is important that you use a single-walled cup so that the heat can easily transfer into the water.

Make sure that the candle flame is positioned in the centre of the cup's bottom with the hottest part of the flame almost touching the cup. You need the water to heat up as quickly as possible to finish the activity before the paper gets too soggy and the water drains or simmers away. With no water, the paper will take the full heat and will catch fire.

We've tried a Bunsen burner, but have found that a candle is more effective (and less likely to set the cup on fire!).

Never leave this experiment unattended.

Discussion

Why doesn't the paper cup burn?
What would happen if you use a double-walled insulating paper cup (the type that coffee is often served in)?

Extensions

Try this with other types of paper. Fold a rectangle of paper into a tray by folding up the four edges and gluing or taping them. Place the empty tray on a tripod to help support it, then add the water before lighting the candle. If you are feeling very confident this is a great lesson starter if you use a banknote.

Links to everyday life

Suits developed for troops and pilots working in hot conditions use a pump to circulate cold water round a network of plastic pipes each as thick as a human artery.

Solar water heating (SWH) is a system for heating water using energy from the Sun. Heat from the Sun (solar energy) is collected by a panel, which is placed on a roof and connected by pipes to a hot-water storage device such as a hot-water cylinder.