A fire extinguisher is an important piece of safety equipment in both the home and lab. You can make your own fire extinguisher using common kitchen ingredients to learn how fire extinguishers work and to learn about gases. Then, apply the Ideal Gas Law to change the characteristics of your homemade fire extinguisher.
How a Fire Extinguisher Works
A fire extinguisher typically deprives a fire of oxygen. If you encounter a fire at home, on a stovetop, for example, you can smother the fire by putting a lid over your pan or pot. In some cases, you can toss a non-flammable chemical on the fire to reduce the combustion reaction. Good choices include table salt (sodium chloride) or baking soda (sodium bicarbonate). When baking soda is heated, carbon dioxide gas is given off, suffocating the fire. In this project, you'll cause a chemical reaction to produce carbon dioxide gas. The carbon dioxide sinks in the air, displacing it and removing oxygen from the fire.
Homemade Fire Extinguisher Materials
- Baking soda (sodium bicarbonate)
- Vinegar (weak acetic acid)
- Jar with lid, with a hole in the lid
Make the Fire Extinguisher
- Fill the jar about halfway full with vinegar.
- To activate the fire extinguisher, drop in a spoonful of baking soda.
- Immediately shake the jar and point the hole of the jar toward your fire.
Test out your fire extinguisher on a candle or small intentional fire so you will know what to expect.
Tips and Tricks
- If you want a directional fire extinguisher, you can insert a straw into the hole in the jar or bottle. Use caulk or duck tape to secure the straw so that it won't shoot out of the jar when you use the homemade fire extinguisher.
- Don't add too much vinegar to the container! You want enough room to add the baking soda and to prevent excessive build-up of pressure.
- You can prepare sachets of baking soda for easier use. Simply wrap a spoonful of baking soda in a piece of tissue or toilet paper. When you're ready to use the fire extinguisher, drop the packet of baking soda into the jar and close the lid.
How to Make a Fire Extinguisher Shoot the Farthest
You can apply the Ideal Gas Law to make a science project out of your homemade fire extinguisher. How would you make the fire extinguisher shoot as far as possible? You do this by maximizing the pressure in the bottle. The pressure in the Ideal Gas Law is related to the volume of the bottle, the amount of gas in the bottle and temperature. Maximize pressure by increasing the temperature and the number of moles of gas inside the bottle.
PV = nRT
P is the pressure in the bottle
V is the volume of the bottle
n is the number of moles of gas in the bottle
R = Ideal Gas Constant
T = temperature Kelvin
Solving for pressure or P, you get:
P = nRT / V
So, to maximize the amount of pressure and thus the distance you can shoot the carbon dioxide, you can:
- Minimize the volume of the container (V). Using a larger bottle may make it easier for you to complete the project, but it won't improve the distance of your homemade fire extinguisher.
- Maximize the amount of gas produced by the chemical reaction (n). You'll need to experiment with the amounts of vinegar and baking soda you use in order to produce the most carbon dioxide. Usually, you'll have plenty of vinegar in a bottle, but not necessarily enough baking soda to react all of it. Also, keep in mind you increase the reaction needed to produce the carbon dioxide when you increase the availability of baking soda by shaking the container to mix the chemicals or by breaking up the baking soda into a fine powder (rather than adding one large clump).
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