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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