Fire: What Makes it Burn (1952)

[Music] what is fire what makes things burn in this film we're going to study fire what it is and what it does we know some things about fire already fire gives us heat it Cooks our food and sometimes provides us with light fire does a great many things that are useful to man but fire can also be dangerous because fire can can be dangerous we'll study it in a laboratory where we can experiment safely what do we need to make a fire let's try to find out here we have a candle some paper and some wood we light the candle with a match the paper burns easily a stick of wood burns too but not so easily as a sheet of paper so one thing we need to make a fire is something that will burn a fuel what else do we need what did we use when we lift the candle a match a match provides heat so a second thing we need to make something burn is heat this is coal a piece of coal will burn in the fireplace will it burn if we hold a match to it no one match won't light a piece of coal this size two won't either nor will three the flame of this gas burner is much hotter soon the coal begins to Glow so it's not just heat we need to make things burn we need enough heat when enough heat is applied to a fuel combustion takes place the temperature needed to make something burn is called its kindling temperature when a fuel reaches its kindling temperature it begins to burn when a fire is started most fuels will continue to burn this paper continues to burn burn when the match is taken away why is that combustion the process of burning produces heat the heat from the small fire we started with a match warms the rest of the fuel to kindling temperature so it begins to burn a sheet of paper catches fire quickly it has a low kindling temperature dry wood also has a fairly low kindling temperature green leaves and twigs have a higher kindling temperature that means they need more heat to burn with this glass rod we can show that some chemicals have a very low kindling temperature the heat from a warm glass rod is enough to start them burning some materials found in the home have very low kindling temp temperatures cleaning fluids and paint thinners can catch fire easily so they should be handled with great care sometimes Rags soaked with these materials can give off enough heat to reach their kindling temperature and begin burning all by themselves when something catches fire without something else lighting it it is called spontaneous combustion almost anything will burn at some temperature even iron will burn when it is ground into to a fine powder and exposed to a flame so will Breck but what is needed to keep things burning when we put a jar over the candle we don't touch either the fuel or the heat still the flame goes out can you guess why the fire needs air that's partly right fire does need something from the air air to burn but what we'll experiment again from the air in this bottle one important part has been removed watch what happens when we pour it over the flame now in another bottle we have that one part that was removed from the air a gas called oxygen when we put a bottle of oxygen over the candle the flame burns more brightly as long as there is oxygen in the bottle so fire needs only that one part of the air we call oxygen in order to burn we've learned that a fire needs three things to burn fuel enough heat and oxygen but what is fire is it a solid no we can move a wire through the flame of the candle then is it a gas maybe the wire moves as easily through the flame as it does through air which is a gas do you notice that the flame isn't the same all over at the top it is yellow at the bottom it is blue are the parts of a flame different in other ways look at the tip of this needle where the yellow and blue Parts meet you can see it glow but does it Glow now no the needle does not glow at the bottom part of the flame that is because some parts of the flame are hotter than other parts an experiment with a glass tube can help us learn why some parts of the flame are hotter we put one end of the tube in the lower part of the flame and hold a match at the other end look carefully and you will see a small flame where does its fuel come from from the candle of course but how unburned gases from the lower part of the flame are carried up the tube where they burn so a flame is made up of both burned and unburned gases the flame is hotter where most of the burning takes place but where do the gases come from the gas comes from the melting candle wax the heat of the flame raises the temperature of the wax until most of it is turned into a gas and it is the gas you remember that is burning we know more about fire now fire occurs when fuel heat and oxygen are combined will what we know help us put out a fire let's take take away the fuel when we separate the flame from the wax there is nothing left to burn and the fire goes out so one way to put out a fire is to remove the fuel can you think of another way to put a candle out let's take away the oxygen when the oxygen in this bottle is used up the fire goes out so another way to put out a fire is to keep away the oxygen and now let's pour water on it why did the fire go out fire is produced when fuel heat and oxygen are combined if we take away one of the three things fire needs to burn the fire will go out water helps put out a fire in two ways water is cooler than fire it cools the burning material below its kindling temperature below the point at at which it will burn and it keeps away the oxygen water will extinguish most fires but water won't always work oil and gasoline will float on water and continue to burn foam from the fire extinguisher covers the flame until it shuts out enough oxygen to smother it in the same way when clothes catch fire rolling up in a blanket keeps oxy away from the fire putting it out even rolling on the floor can smother the flame but running is dangerous it supplies more oxygen to the fire yes fire can be dangerous if you see a fire and an adult is not nearby call the fire department stay calm and speak clearly give them the address and tell them what is burning you can't be too careful with with fire even a small fire can be dangerous here there is a lot of fuel and the Flames are spreading creating more and more heat the wind provides plenty of oxygen so the fire grows quickly look around you will see fire used everywhere to keep you warm to cook your food even to weld metals and turn machines but a fire any fire can be dangerous so it is important to understand fire and to obey safety rules in the home and Out of Doors