Skip to content
Exit presentation

Changes Around Us: Physical and Chemical

One candle, two changes at once

A candle is lit. A pool of clear wax forms around the wick, the candle's thread.

Loading lab…

The idea

Wax vapour is wax as a gas.

Candle lit. Wax melts near the wick.
Step 1 of 4
  1. Candle lit. Wax melts near the wick.
  2. The pool of melted wax grows.
  3. Hot wax turns to vapour. The vapour burns.
  4. Blown out. The pool sets hard again. The burned wax does not return.

The rule

Wax melting is physical. Wax vapour burning is chemical. A candle has both.

What happens to the wax, step by step
StepKind of change
Solid wax meltsPhysical
Melted wax climbs the wickPhysical
Hot wax turns to vapourPhysical
The vapour burnsChemical
The pool sets hard againPhysical

Melting comes first. Without melting, the wax cannot reach the flame.

Jump to lesson

This track

  1. 0 Start here
  2. 1 Fold it, cut it, crumple it
  3. 2 Ice, water and steam are one substance
  4. 3 Dissolving is not disappearing
  5. 4 Some of these will not go back
  6. 5 Checkpoint: changes that make nothing new
  7. 6 A test for something new
  8. 7 Five signs, and what each one is worth
  9. 8 One candle, two changes at once
  10. 9 Two questions, not one
  11. 10 Slow changes in rocks
  12. 11 Checkpoint: new substances and the two questions
  13. 12 Burning needs air
  14. 13 The fire triangle
  15. 14 A change written in words
  16. 15 Useful and harmful changes
  17. 16 Checkpoint: burning, equations and useful changes
  18. 17 The big picture
  19. 18 Track quiz

Other tracks