Science talk With Chris Duggan House of Science

Chris Duggan is a scientist, educator, mother of two adult daughters, and farmers wife. After many years teaching secondary school Science and Chemistry, she switched her focus to primary schools by setting up a charity called House of Science in 2013. This large organisation supports thousands of teachers with science resource kits and professional development.

See what Chris has to say in her latest blog below.

Ever wondered how a fire extinguisher works? Often when we think of extinguishing fires – water comes to mind. However, most fire extinguishers don't contain water. Most extinguishers release a layer of foam that stop air from reaching the flames.

In this fun activity, you will learn how baking soda and vinegar can put out a candle flame. No need for a real fire extinguisher in this activity.

This science experiment is also great for developing observation and questioning skills.

NB: This activity will need an adult assisting.

Materials:

· Small Candle (Tea Light Candle is preferred)

· Matches

· Vinegar

· Baking Soda

· Tablespoon

· Drinking glass or glass dish to place your candle in. (The top of the candle must be lower than the top of the dish)

· Water

Photo: Supplied.

Instructions:

1. Place the candle in the centre of your glass or dish.

2. Sprinkle a couple of tablespoons of baking soda around the candle. The bottom of your glass or dish needs to be fully covered with a thin layer of baking soda.

3. With the help of an adult, light the candle with a match. Observe the flame for a couple of seconds.

What does the flame look like? Is it big or small?

4. Carefully pour a small amount of vinegar into the glass or dish onto the baking soda, making sure that no liquid or foam reaches the flame.

What happens when you add the vinegar to the baking soda?

5. Once you have added the vinegar, watch your candle carefully.

What happens to the flame? Does the candle keep burning?

NB- If you do not see anything happening, add a bit more vinegar to the glass/dish.

6. Once your flame has gone out, try and re-light your candle with the match.

Is it easy or hard to do? What happens when the match gets too close to the candle?

7. Clean out your glass/dish and repeat the experiment again, but this time instead of adding vinegar to baking soda – just add water.

What has happened to the flame this time around? Is it the same reaction as before, or different?

8. Make sure you put out the candle and remember to rinse out the glass/dish with water and soap.

The Science Behind the Fun:

Did you successfully extinguish your flame?

What do you think happened?

The answer has to do with the chemical reaction that occurs when you mix vinegar with baking soda.

Baking soda is a chemical compound called sodium bicarbonate and it reacts with any type of acid such as vinegar to form a gas called carbon dioxide (CO2).

For a flame to burn it needs fuel, heat, and oxygen. Carbon dioxide is a colourless gas that is slightly heavier than air.

Although we can't see it, the CO2 gas that is produced in the reaction starts filling the glass/dish from the bottom up. Eventually, once all the air in the glass/dish is replaced by carbon dioxide, the flame no longer has enough oxygen to burn, and it will go out. If you were to try and light the candle again, it won't work because the match also goes out once it enters the layer of carbon dioxide in the glass/dish.

Something Extra:

What other acidic liquids in your kitchen, besides vinegar, make carbon dioxide when mixed with baking soda? Observe your candle when adding these liquids to the baking soda.