Parental Note: This experiment is geared toward ages 8 and up. Adult supervision is needed to mix substances and to light a candle safely.
Additional Note: This activity will take about 20 minutes to complete.
Carbon dioxide is a colorless and odorless gas. As you may have learned from the photosynthesis experiment, carbon dioxide is a useful gas because it is taken up by plants to help them make food and produce oxygen. You may have also learned that carbon dioxide is a greenhouse gas and that there is too much carbon dioxide in the Earth’s atmosphere from burning fossil fuels, causing rapid climate change.
Today we’re going to learn one more interesting fact about the gas known as carbon dioxide—it can be used to put out fires! In fact, carbon dioxide is used in many fire extinguishers because it can put out liquid fires, gaseous fires, and electrical fires.
You are going to make your own carbon dioxide fire extinguisher using a few at-home ingredients. Then, you will use the built-up gasses to put out a candle flame.
Before starting the experiment, answer the following questions:
- What are some signs that a chemical reaction is taking place?
- Transparent glass bottle with a small neck
- Baking soda (sodium bicarbonate)
- Vinegar (weak acetic acid)
- Small candle (tea light candle will do)
Light the candle.
Mix 2 tablespoons of baking soda and 2 tablespoons of vinegar together in the glass bottle. You might start to hear a fizzing sound right away. This is a sign that a chemical reaction is taking place.
Put your hand over the mouth of the glass bottle to prevent the carbon dioxide from escaping. With your hand covering the opening, wait a few moments for the chemical reaction inside the bottle to slow down.
Keeping your hand firmly over the bottle’s opening, tilt it to the side and put the mouth of the bottle right next to the candle’s flame. Then remove your hand from the mouth of the bottle and allow the air inside the bottle to escape. Be careful not to spill the liquid. Observe what happens to the flame.
Share Your Results:
- What happened when you mixed the baking soda and vinegar together in the bottle?
- What happened when you removed your hand from the top of the bottle?
When you mix baking soda and vinegar together, you produce carbon dioxide. Carbon dioxide is a clear, odorless gas that is important for photosynthesis and supporting plant life on Earth. Carbon dioxide is denser than air and can displace lighter gasses such as oxygen. Oxygen is fuel for a fire because it supports the chemical processes that take place during a fire. When you released the carbon dioxide from the bottle, it displaced the air containing oxygen that was feeding the candle flame. This “suffocated” the fire and caused the flame to go out. This is a very simple representation of how a fire extinguisher works!