Reactions that heat up or cool down

Science · Matter & Materials · ages 12-13

Name ______________________ Date ____________

In an exothermic reaction, energy moves...
- from the surroundings into the reaction
- from the reaction into the surroundings
- It stays inside the reaction and never moves
Burning wood is an example of an exothermic reaction.
Circle one: True False
Which best describes an endothermic reaction?
- It absorbs energy and the temperature falls
- It releases energy and the temperature rises
- It has no energy change at all
Which statement about melting and freezing is correct?
- Melting releases energy, so it is exothermic
- Melting absorbs energy, so it is endothermic
- Melting and freezing both release energy
Which change of state is exothermic?
- Ice melting into water
- Water freezing into ice
- Water evaporating into vapor
A beaker reads 21°C before a reaction and 9°C after it. How many degrees did the temperature drop?
Answer: ______________
Which pair correctly matches an exothermic example with an endothermic example?
- Striking a match (exothermic); a sports cold pack activating (endothermic)
- Photosynthesis (exothermic); burning wood (endothermic)
- Freezing water (endothermic); melting ice (exothermic)
Mia tests a reaction. The temperature drops from 25°C to 10°C, but she writes 'this reaction is exothermic because I saw bubbles.' What is her mistake?
- She should have used the temperature drop to call it endothermic, not the bubbles
- She should have used the bubbles to call it endothermic too
- She is correct, since bubbles always mean exothermic

Answer key

For grown-ups. Fold this page away before handing over the rest.

from the reaction into the surroundings · Exothermic reactions push energy out into the surroundings, which is why the temperature rises.
True · Burning wood releases heat you can feel, so it's exothermic.
It absorbs energy and the temperature falls · Endothermic reactions take energy in, so the surroundings feel cooler.
Melting absorbs energy, so it is endothermic · Melting needs energy to loosen the particles in a solid, so it takes energy in from the surroundings.
Water freezing into ice · Freezing releases energy into the surroundings, so it's exothermic.
12 · 21 minus 9 is 12. A drop in temperature means the reaction absorbed energy, so it's endothermic.
Striking a match (exothermic); a sports cold pack activating (endothermic) · A match releases heat, so it's exothermic. A cold pack absorbs heat, so it's endothermic.
She should have used the temperature drop to call it endothermic, not the bubbles · Bubbles alone don't tell you the reaction type. A temperature drop means the reaction absorbed energy, so it's endothermic.