Putting fires out

Teachers’ note

With wooden buildings and thatched roofs fire was an ever-present danger in Viking times, especially as the hearth in the centre of the main room is where the open fire would be lit. Sparks from the fire could easily set fire to the thatch without proper precautions. In case of fire, buckets of water could be thrown onto the blaze to extinguish it, or cloaks thrown over smaller fires to smother them.

What can we ask?

How can we use vinegar and sodium bicarbonate to make a fire extinguisher?

Equipment list

Vinegar, baking soda (sodium bicarbonate), 1-litre jug, spoon, tea light candles, lighter.

Activity instructions

Light a tea light candle with the lighter. Measure approximately 100 ml of vinegar into the jug. Add a couple of teaspoons of sodium bicarbonate and wait until the fizzing stops. Carefully tip the jug over the candle, but don’t let any liquid come out. The candle should go out.

Explanation

The vinegar and sodium bicarbonate react to produce carbon dioxide, an invisible gas which is heavier than air. When you tip the jug you pour the carbon dioxide over the flame, cutting off the oxygen and smothering the flame.

Health and safety

Wear safety glasses. Ensure no flammable materials are within 1 m of the candle flame. Use tealights rather than taller candles as these can fall over. Take care to avoid long hair or loose clothing coming into contact with flames.

Health & Safety checked, 2019