Chemical reactions and energy changes
Learn Chemical reactions and energy changes for Year 9 pupils (ages 13–14). Free practice questions, lessons and worked examples — aligned to the UK National Curriculum.
What you'll learn
- 1
In a chemical reaction, atoms are rearranged. None are created or destroyed.
- 2
Exothermic reactions release energy and warm the surroundings — burning, neutralisation. Endothermic reactions take energy in and feel cold — like a sports cold pack.
- 3
Why does a burning candle seem to lose mass?
- 4
A reaction that takes in energy and feels cold is:
- 5
Apply it: mass is conserved. 24 g of magnesium burning in 16 g of oxygen makes 40 g of magnesium oxide. Nothing is created — the atoms are only rearranged.
- 6
10 g of a metal reacts fully with 4 g of oxygen. What mass of oxide forms?
- 7
A reaction appears to lose mass. What is the usual reason?
Practise Chemical reactions and energy changes with Whizlo
Free AI-tutored lessons, unlimited practice questions, and progress tracking for ages 13–14. Aligned to the UK National Curriculum.