Set up time
5 mins

What you need
Tealight candle, plate, matches, glass beaker, vinegar, baking soda, funnel

Aim
To demonstrate the effect that carbon dioxide has on a flame. Using the components of a fire: heat, fuel and oxygen, this experiment will show how carbon dioxide starves oxygen.


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Learning outcomes

1

Your students will observe the effect that carbon dioxide has on a flame, and learn that fire needs oxygen to stay alight.

2

Before watching your demonstration, your students will learn how to make predictions about the experiment.

3

After the demonstration, your students will learn how to record the results and suggest reasons why the flame went out.

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Instructions

Carbon dioxide is all around us. Plants convert carbon dioxide into oxygen and all life on earth needs oxygen to survive. It can come from volcanoes, hot springs, geysers and can also be found in oceans. We use carbon dioxide to make fizzy soft drinks and help make bread rise.

We also use carbon dioxide to manage fires. What happens when you add carbon dioxide to a fire? 

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Place a tealight candle on a plate and light the candle.

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In a glass beaker, mix ¼ cup of vinegar and a tablespoon of baking soda. It will fizz up immediately, filling the beaker with carbon dioxide bubbles.

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When the fizzing stops, ‘pour’ the carbon dioxide gas down a v-shaped funnel towards the flame, taking care not to pour any liquid.

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Watch the flame go out when it gets smothered in carbon dioxide.


What do you think will happen when we ‘pour’ the carbon dioxide onto the flame?
Why do you think the carbon dioxide ‘pours’ out before the liquid in the jar?

Time required
30 mins


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Extension

This incredible video from NASA shows how carbon dioxide in the atmosphere travels around the globe over 12 months. Your students can watch the carbon dioxide levels rise and fall during the year.

A Year in the Life of Earth's CO2

1

Watch the changing colours in this video, while also looking at the month in the bottom left corner. You’ll see how the carbon dioxide builds up, and then decreases, and then builds up again.

2

The gas doesn’t stay in one place. Instead, it swirls around the globe – this effect is due to the changing weather patterns.

3

About half of the carbon dioxide released from burning fossil fuels stays in the atmosphere. The other half is absorbed by plants during spring and summer.

4

When humans and other animals breathe, we take in oxygen and breathe out carbon dioxide.