A student mixes two chemicals in a beaker and the beaker gets noticeably hotter. What type of reaction is occurring?
AEndothermic
BExothermic
CNuclear
DPhysical change
If the beaker gets hotter, the reaction is releasing energy (heat) into the surroundings. Reactions that release energy are exothermic. In an endothermic reaction, the beaker would get cooler because the reaction absorbs heat from the surroundings.
Question 2 True / False
An endothermic reaction releases heat into the surroundings.
TTrue
FFalse
Answer: False
Endothermic reactions absorb heat from the surroundings, causing the surroundings to cool down. It is exothermic reactions that release heat. The prefix 'endo-' means 'into' (energy goes into the reaction), while 'exo-' means 'out of' (energy comes out of the reaction).
Question 3 Short Answer
Explain why an instant cold pack feels cold when you activate it.
Think about your answer, then reveal below.
Model answer: The chemical reaction inside the cold pack is endothermic — it absorbs heat from your skin and the surrounding area, making it feel cold.
Instant cold packs typically contain ammonium nitrate and water separated by a barrier. When the barrier is broken and they mix, the dissolving process absorbs energy from the surroundings. Your skin loses heat to the pack, which is why it feels cold. The cold is not being created — heat is being absorbed.