Materials needed, per student
- Pipe clay triangle
- Paper cup
- Teaspoon of hot chocolate powder (optional)
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 centred beneath the cup 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.
This activity works with a Bunsen burner, but we have found that a candle is more effective and is less likely to set the cup on fire!
Never leave this activity unattended.
- 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)?
- Try this with other types of paper. Make 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 support it, then add water before lighting the candle. If you are feeling very confident us a banknote for a great lesson starter!.
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 systems use the same principles of energy transfer to heat water using solar panels to harness energy from the Sun.