What burns?
Hold things in a flame: some burn, some only get hot.
Into the flame
A teacher holds things in a flame with tongs: wood, paper, cotton, kerosene, stone, glass, sand and brick.
Which of them will catch fire?
What this lesson covers
The idea
Combustion is a chemical reaction in which a substance reacts with oxygen and produces heat and/or light; substances that undergo combustion are called combustible substances.
Into the flame
A teacher holds things in a flame with tongs: wood, paper, cotton, kerosene, stone, glass, sand and brick.
Which of them will catch fire?
- All of them
- Some of them
- None of them
Burn or only hot?
Tap a thing on the shelf. The tongs hold it in the flame. Does it catch fire, or does it only get hot?
Combustion
The things that burned reacted with oxygen in the air and gave out heat and light. Getting hot is not enough: stone, glass, sand and brick got hot, but they did not burn.
A chemical reaction in which a substance reacts with oxygen and produces heat and/or light is called combustion. Substances that undergo combustion are called combustible substances. For example, wood, paper, cotton and kerosene are combustible substances.
- In the flame | What happened | Given out
- Wood, paper, cotton, kerosene | caught fire and burned | heat and light
- Stone, glass, sand, brick | only got hot | no burning
Notes
Combustion is a chemical reaction in which a substance reacts with oxygen and produces heat and/or light. Substances that undergo combustion are combustible substances: wood, paper, cotton, kerosene.
Check yourself
Which of these is a combustible substance?
Combustion is a chemical reaction in which a substance reacts with _ and gives out heat and/or light.
A brick is held in a flame. It gets very hot. Is brick a combustible substance?
Wood, paper, cotton, kerosene, stone, glass, sand and brick were held in the flame. How many of them are combustible substances?
Answer: 4
Four: wood, paper, cotton and kerosene caught fire. The other four only got hot.
- Sand on the beach. Sand only gets hot in a flame. It does not burn.
- Cotton cloth — correct. Yes! Cotton catches fire and burns.
- A glass tumbler. Glass only gets hot. It does not burn.
- water. Burning needs oxygen, not water.
- carbon dioxide. Carbon dioxide is not what a burning thing reacts with.
- oxygen — correct. Yes! The oxygen comes from the air.
- No, it does not burn — correct. Yes! It only gets hot. It does not react with oxygen and burn.
- Yes, because it gets hot. Getting hot is not enough. A combustible substance burns.
- Yes, because the flame touched it. Anything can be held in a flame. Only some things burn.