Flashcards in 4.9 Using Energy Transfers From Reactions Deck (9)
In the hand warmers that can only be used once, what are 2 common reactions used for them?
•oxidisation of iron
•calcium oxide with water
Reactants are used up so can only be used once
In the hand warmers that can be used multiple times, what are common reactions used for them?
•crystallisation of a salt
How can we get the heat packs to re dissolve the salt?
Heat it in boiling water, can be used many times
Suggest one advantage and one disadvantage of using reusable hand warmers instead of single use hand warmers
Pro: less resources wasted
Con: needs energy to be heated again
Name a practical use of endothermic reactions?
How do cold packs work?
Ammonium nitrate and water are kept separately. When mixed together the endothermic reaction takes place, taking in energy from the surroundings and becoming very cold. The reaction can't be undone so can only be used once
Name 2 ways ice packs can be used
•on sports injuries
•to cool drinks
Suggest one advantage and one disadvantage of using chemical cold packs instead of an ice pack
Pro: can be used anywhere
Con: only be used once so wastes resources