For this week's science lesson, we will look at what fire needs to burn and how to extinguish them.
Fire needs 3 things in order to continue burning: heat, oxygen, and some kind of fuel. In order to extinguish (vocabulary word) a fire, you need to remove one of those three things. Many commercial fire extinguishers work by either cooling the fire/fuel and/or by displacing the oxygen around the fire. How Stuff Works has a video showing how to use an extinguisher and gives a brief explanation of how the actual extinguisher works. It may not keep the attention of younger kids, but it is only a little over a minute so it shouldn't be too bad.
When your clothes are on fire, you are taught to stop, drop, and roll. This is done because it removes the oxygen from the fire. It is also why you are told to throw a blanket on a person whose clothes are on fire and then have them drop and roll. Running with your clothes on fire simply adds more oxygen to the fire, causing it to burn more.
Grease fires are a bit different to deal with simply due to the fact that water and grease repel(another great vocabulary word) each other. It is important to know that you cannot extinguish a grease fire with water. If the fire is in a pan or pot, slide a lid onto it to cut off the oxygen to the fire and turn off the heat source. Alternatively, throw baking soda on the fire (this also works for electrical fires) to smother the fire by removing the oxygen. This happens because the baking soda decomposes and releases CO2 which replaces the oxygen. If there is a fire in the oven, close the door and turn off the heat. This should extinguish the fire by removing the oxygen supply.
In any event, if the fire is too big to put out or you are unable to put it out quickly, get out of the house and call 911. It is also advisable to have fire extinguisher(s) on hand as they are easier and more effective than other methods.