Follow these instructions to carry out a fiery chemical trick.
SafetyThis activity involves fire. See the Safety for DIY science activities for more information.
You will need
- glass jar
- rubbing alcohol (a mixture of isopropanol and water) from a supermarket or chemist
- small rectangle of paper - Monopoly money works really well
- container of water.
What to do
- Place the money into the glass jar.
- Carefully pour rubbing alcohol over the paper, so that the whole piece is soaked.
- Use the tongs to pick up the paper, and shake off any excess liquid.
- Hold the tongs at arm’s length, and use the candle to light the paper.
- Continue to hold the tongs, move away from the candle and let it burn. If the paper itself starts to burn, drop it into the water.
- When the paper has stopped burning, look at it. What do you see?
Rubbing alcohol consists of two liquids mixed together: isopropanol (a type of alcohol) and water. Isopropanol is highly flammable, while water is not. The flammability of paper is in between.
When you light the paper with the candle, the isopropanol starts burning and produces heat. Normally this heat would be enough to start burning that paper. Water doesn’t burn, and is very good at absorbing heat, especially as it evaporates. As the isopropanol burns, the heat is absorbed by the water, not the paper. Paper needs a temperature of around 230°C in order to burn.
In this activity, the temperature only reaches about 210°C, so the paper doesn’t burn.
Cars, trucks, planes and lawn mowers all use different fuels to work. All these fuels are flammable, but they all burn at different temperatures. The engines in these machines are designed for a particular fuel. If you put the wrong fuel into an engine (for example, putting diesel into a car designed for petrol), it won’t work properly and may damage the vehicle.
Water’s ability to absorb heat is one of its most useful properties. Large bodies of water, such as oceans and lakes, require more heat to raise their temperature than the ground and air. This is why on hot summer days it’s fun to cool off at the beach: the temperature of the water is lower than the air. By absorbing heat from the Sun and transporting it through currents, oceans also play an important role in the Earth’s climate.
This ability to absorb large amounts of heat also has many man-made applications. For example, water is used as a coolant in fields as diverse as oil refining, electricity production and manufacturing.
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