Exothermic and Endothermic reactions

Question 1

What is an Endothermic reaction?

Answer 1

releases energy into the environment

Question 2

What is an Exothermic reaction?

Answer 2

takes energy from the environment to react

Question 3

What are examples of Exothermic reactions?

Answer 3

candle burning-> combustion
neutralisation
respiration

Question 4

What are examples of Endothermic reactions?

Answer 4

photosynthesis
thermal decomposition
reaction of citric acid and sodium hydrogencarbonate

Question 5

How do Hand warmers work?

Answer 5

the salt used in hand warmers is sodium ethanoate
- a supersaturated solution is made by dissolving as much of the salt as possible in hot water, and then cooling this
- small particles are scraped off when you press on the small metal disk inside, starting an exothermic reaction - crystallisation - which lasts for around half an hour
- to reuse the hand warmer you put the pack in hot water to redissolve the crystals

Question 6

How do self heating cans work?

Answer 6

calcium oxide+ water –> calcium hydroxide
press a button at the base to release the calcium oxide into the water

Question 7

How do icepacks work?

Answer 7

when ice packs are struck or squeezed, a bag breaks releasing ammonium nitrate into water which absorbs energy –> works for around 20 minutes

Question 8

What is Bendomex?

Answer 8

BENDOMEX
BREAKING
IS ENDO
MAKING
IS EXO