C5 - Energy Changes Flashcards
(21 cards)
Front
Back
What is an exothermic reaction?
A reaction that releases energy to the surroundings, usually as heat.
What is an endothermic reaction?
A reaction that takes in energy from the surroundings.
What happens to temperature in an exothermic reaction?
It increases.
What happens to temperature in an endothermic reaction?
It decreases.
Give two examples of exothermic reactions.
Combustion and neutralisation.
Give two examples of endothermic reactions.
Thermal decomposition and the reaction of citric acid with sodium hydrogencarbonate.
What is activation energy?
The minimum energy needed for particles to react.
What is the energy profile of an exothermic reaction like?
Products have less energy than reactants; energy is released.
What is the energy profile of an endothermic reaction like?
Products have more energy than reactants; energy is absorbed.
What does a reaction profile show?
The energy of the reactants and products during a chemical reaction.
How can you measure energy change in a reaction?
By recording the temperature change using a thermometer.
What is a simple example of an exothermic everyday use?
Hand warmers.
What is a simple example of an endothermic everyday use?
Instant cold packs.
What is bond breaking?
An endothermic process where energy is taken in to break bonds.
What is bond forming?
An exothermic process where energy is released when new bonds form.
What is the overall energy change in a reaction?
Energy in (for breaking bonds) - Energy out (from bond formation).
When is a reaction exothermic in terms of bonds?
When more energy is released making bonds than is needed to break bonds.
When is a reaction endothermic in terms of bonds?
When more energy is needed to break bonds than is released making them.
What is the unit for measuring energy change?
Joules (J) or kilojoules (kJ).
Why are insulated containers used in energy change experiments?
To reduce heat loss or gain from the surroundings.
