Energy Transfer in Reactions Flashcards

All 8 cards in this deck

What is an exothermic reaction?

A reaction that transfers energy to the surroundings, so the temperature of the surroundings increases.

What is an endothermic reaction?

A reaction that takes in energy from the surroundings, so the temperature of the surroundings decreases.

Name three types of reaction that are exothermic.

Combustion, many oxidation reactions and neutralisation.

Give two examples of endothermic reactions.

Thermal decomposition, and the reaction of citric acid with sodium hydrogencarbonate.

Which type of reaction is used in hand warmers and self-heating cans?

Exothermic — energy is transferred to the surroundings, warming them up.

True or false? A sports injury cold pack works using an exothermic reaction.

False. Some sports injury packs use an endothermic reaction, which takes in energy and cools the surroundings.

In an exothermic reaction, how does the energy of the product molecules compare with the energy of the reactants?

The products have less energy than the reactants, by the amount of energy transferred to the surroundings (energy is conserved).

True or false? In an exothermic reaction some energy is destroyed, so there is less energy in the universe after the reaction.

False. Energy is conserved — the total energy in the universe is the same before and after; it is only transferred to the surroundings.