WONDER #1338: Why Does Wood Crackle When It Burns?

Question 1 of 3

What basic element in the air is required for fire?

1. oxygen
2. nitrogen
3. hydrogen
4. helium

Question 2 of 3

A combustion reaction will occur when a source of fuel is heated to what point?

1. boiling point
2. melting point
3. ignition temperature
4. freezing point

Question 3 of 3

The decomposing cellulose material of burning wood takes several forms, including all but which of the following?

1. volatile gases
2. char
3. ash
4. bark

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