A candle is burning inside a sealed glass jar. After a short time, the flame goes out. Why?
AThe candle got too hot and melted completely
BThe candle used up all the oxygen inside the jar, so burning could not continue
CThe glass blocked the light from reaching the flame
DThe jar trapped too much smoke, which put the fire out
Burning requires oxygen. Inside the sealed jar, the flame used up the available oxygen. Once the oxygen was gone, the burning reaction could not continue, and the flame went out. This demonstrates one side of the fire triangle — remove the oxygen and the fire stops.
Question 2 True / False
When wood burns, the matter in the wood is substantially destroyed.
TTrue
FFalse
Answer: False
False. The matter is not destroyed — it is transformed into new substances. Burning wood produces ash (a solid), carbon dioxide (a gas), and water vapor (a gas). If you could collect all the ash, gases, and vapor, their combined weight would actually be more than the original wood because oxygen from the air joined the reaction.
Question 3 Short Answer
What three things are needed for fire to exist?
Think about your answer, then reveal below.
Model answer: Fuel (something to burn, like wood or paper), oxygen (from the air), and heat (enough to start the reaction). These three are called the fire triangle.
The fire triangle explains both how fires start and how they can be stopped. Remove the fuel (clear the area), remove the oxygen (smother with a blanket or use a fire extinguisher), or remove the heat (spray with water) — take away any one of the three and the fire goes out.