1. Making electricity
A cell is an arrangement where chemical energy is converted into electrical energy.
In a cell a pair of different metals are connected with an electrolyte between them.
The different metals have different voltages.
The metal higher in the electrochemical series( p7 data book) always donate electrons to the metal lower.
This will continue as long as the electrolyte is present.

2. Batteries A battery is a collection of cells.
A battery will convert chemical energy into electrical energy until the chemicals are used up.
There are many types of battery.

3. Examples of Batteries Battery Use Advantage Disadvantage Zn/C
Torch, clock
Cheap
Leaks
Pb/H+
Cars
Rechargeable
Needs topped up
Ni/Cd
Torch
Care recharging/Cd poisonous.
Lithium
Pacemaker
Non toxic
Li reactive
Ag2O
Watches
Long lasting
Expensive

4. The Electrochemical Series
Puts metals in order of the ease with which they loose electrons.
The metals at the top give electrons most readily.
We can predict a metals position using simple cells and metal pairs.
We use one metal as a standard – i.e. one of the pair is always the same metal.

5. Voltage
The further apart 2 metals are in the electrochemical series – the greater the voltage they produce when arranged in a cell.
Example – Cu is the standard
Metal
Voltage Mg
2.7 Zn
1.1 Cu
0.0 Ag
- 0.5

6. Displacement Reactions
When a metal higher up in the electrochemical series is placed in a solution of the ions of a metal lower in the series.
Example
Zinc + Copper sulphate —> Zinc sulphate +
Copper
The Zinc takes the place of the Copper ions in the solution, Cu solid appears.

7. Oxidation and Reduction
OILRIG
Oxidation is loss of electrons
Reduction is gain of electrons
Oxidation and reduction always happen together.
REDOX is what we call the whole thing – oxidation and reduction.

8. Ion Electron Equations
Oxidation
The electrons are always on the RHS of the arrow
Example
Cu atoms being oxidised to Cu ions
Cu(s) —> Cu 2+ (aq) + 2e
Iodide ions loosing electron to form Iodine molecule
2I- (aq) —> I2 ( s) + 2e

9. Reduction The electrons will always be at the LHS of the arrow.
Example
Mg ions gain 2 electrons to form Mg atoms.
Mg 2+(aq) e —> Mg(s)
Cl2 molecule gaining 2 electrons to form ions
Cl(g) + 2e —> 2 Cl- (aq)

10. REDOX
Example
Magnesium reacting with Hydrochloric Acid to form Magnesium chloride and Hydrogen gas.
Oxidation
Mg (s)—> Mg 2+ (aq) e
Reduction
2H+ ( aq) + 2e —> H2 (g)
Redox
Mg ( s) + 2H+ (aq) + 2e —> Mg 2+ (aq) + 2e +
H2 (g)