Energy Changes

A reaction that transfers energy to the surroundings, usually as heat. The surroundings feel warmer

Combustion and neutralisation

A reaction that takes in energy from the surroundings: the surroundings feel cooler

Thermal decomposition and photosynthesis

the energy needed for a chemical reaction to happen

Pros: last longer, cheap to purchase and no charging required
Cons: bad for the environment and expensive to produce

Pros: better for the environment, one time purchase, less manufacturing
Cons: last less longer and use fossil fuels

- 2 metals (1 very reactive and 1 unreactive), an electrolyte, wires and a voltmeter

Benefits: environmentally friendly, quicker at charging, travel further
Drawbacks: hard to store hydrogen, highly flammable

The more reactive metal loses electrons and is oxidised; the less reactive metal gains electrons and is reduced & a higher voltage is produced