C7 energy changes

Question 1

exothermic reaction

Answer 1

transfers energy to environment from reactants eg. burning, neutralisation, hand warmers

Question 2

energy change in exothermic

Answer 2

products have lower energy content than reactants

Question 3

endothermic reaction

Answer 3

transfer energy from surroundings to reactants eg. decomposition, instant cold packs

Question 4

energy change in endothermic

Answer 4

products have higher energy content than reactants

Question 5

activation energy

Answer 5

minimum energy required for a reaction to start ( colliding particles have sufficient energy to cause a reaction)

Question 6

bond making

Answer 6

exothermic

Question 7

breaking bonds

Answer 7

endothermic- energy required to break them ( has to be transferred from environment)

Question 8

calculating energy change for chemical reaction

Answer 8

work out:
1) energy required to break bonds in reactants
2) energy released when new bonds are formed in products

Question 9

metals in cells and batteries

Answer 9

greater difference in reactivity of two metals, higher voltage produced