Reactions that release or absorb energy
Grade 10 Science Worksheet
Circle the best answer, or write your answer on the line.
An energy diagram shows the reactants at 120 kJ, the top of the hill at 180 kJ and the products at 40 kJ. What is the activation energy, Ari?
An energy diagram shows the reactants at 200 kJ, the top of the hill at 260 kJ and the products at 150 kJ. What is the activation energy, Esme?
H₂ + Cl₂ → 2 HCl has ΔH = −184.6 kJ. What is ΔH for 2 HCl → H₂ + Cl₂, Jun?
- −184.6 kJ
- 0 kJ
- +184.6 kJ
Melting ice absorbs heat. What sign does ΔH have when water freezes, Kira?
- Zero: it stays at 0 °C
- Negative: freezing releases heat
- Positive: freezing absorbs heat
In a reusable hand warmer, sodium acetate crystallizing is exothermic. What happens when it is reheated to redissolve, Luz?
- No heat moves
- It absorbs heat
- It releases heat
Where does an instant cold pack get the heat it absorbs, Milo?
- From the ammonium nitrate itself
- From the empty air inside it
- From the skin and surroundings
An exothermic reaction happens in water. What happens to the water's temperature, Noah?
- It rises
- It falls
- It stays the same
Ammonium nitrate dissolves and the water cools from 24.9 °C to 20.3 °C. Is the dissolving exothermic or endothermic, Pia?
- Exothermic: the water cooled
- Exothermic: the solid vanished
- Endothermic: the water cooled
On an energy diagram, what does a catalyst change, Ren?
- It changes ΔH
- It raises the products
- It lowers the hill
Burning a match is exothermic. Why must it be struck before it burns, Tala?
- Burning is endothermic
- It must climb the hill first
- Striking adds the products