GCSE Chemistry: energy changes

Flashcards covering key concepts from GCSE Chemistry on Atomic Structure and the Periodic Table.

Exothermic reaction

A reaction that releases energy to the surroundings, usually as heat.

Endothermic reaction

A reaction that absorbs energy from the surroundings.

Activation energy

The minimum energy needed for particles to react.

Reaction profile

A diagram showing the energy changes during a chemical reaction.

Bonds breaking energy

Endothermic energy is needed to break bonds.

Bonds making energy

Exothermic energy is released when bonds form.

Overall energy change formula

Energy change = total energy to break bonds - total energy to make bonds.

Negative energy change

Indicates the reaction is exothermic.

Positive energy change

Indicates the reaction is endothermic.

Simple cell

Produces electricity by connecting two different metals in contact with an electrolyte.

Battery

Two or more cells connected in series to produce a greater voltage.

Rechargeable batteries

Batteries that can be reused, reducing waste and cost.

Non-rechargeable batteries disadvantages

They contain harmful chemicals and contribute to waste.

Fuel cell

A cell that produces electricity by reacting a fuel with oxygen.

Hydrogen fuel cell

A cell that combines hydrogen and oxygen to produce water and release energy.

Half equations in a hydrogen fuel cell

Anode: H 2H + 2e; Cathode: O + 4H + 4e 2HO.

Hydrogen fuel cells advantages

Only water is produced, efficient, lightweight, quick refuelling.

Hydrogen fuel cells disadvantages

Hydrogen is explosive, difficult to store, and expensive to produce.