C7.2 - Using Energy Transfers From Reactions (Finished) Flashcards
How do chemical cooling packs normally work?
With ammonium nitrate and water, when the ammonium nitrate dissolves it absorbs energy cooling the surroundings
What are instant cold packs used for?
Emergency treatment of injuries.
What is the problem of self heating cans?
- A third of the space is taken up by reactants
- It cost millions of pounds to develop
What is the exothermic reaction use din self-heating cans?
Calcium oxide + water -> calcium hydroxide
A button at the bottom breaks a seal letting them mix
What is the chemical rection in a single use heat pack
Iron turning into hydrated iron(III) oxide with sodium chloride as a catalyst
How do reusable heat packs work?
The formation of crystals from a solution of a salt. The solution is prepared by dissolving in hot water, a small metal disk is used to start the exothermic reaction, as when you press it a few times metal particles are rubbed off seeding the crystalisation
What is the advantage of single use hand warmers?
They last a lot longer (for hours vs 30 mins)
