Electrode – IGCSE Chemistry Definition

An electrode is a conductor through which electric current enters or leaves an electrolyte. Every electrolysis setup requires two electrodes — an anode (positive) and a cathode (negative). The 0620 syllabus expects you to know what electrodes are made of, why the material matters, and how the choice of electrode affects the products.

The 0620 definition

An electrode is a solid conductor that carries electric current into or out of an electrolyte during electrolysis. Electrodes are usually made of metal or carbon (graphite).

The two electrodes

Electrode	Charge	Connected to	Attracts	Process
Anode	Positive (+)	Positive terminal of battery	Anions (negative ions)	Oxidation
Cathode	Negative (-)	Negative terminal of battery	Cations (positive ions)	Reduction

Electrode materials

Inert electrodes (most common in 0620)

Inert electrodes do not react with the electrolyte or the products. They simply provide a surface for the reaction and a pathway for the current.

• Carbon (graphite): conducts electricity, high melting point, inert. Most common choice for IGCSE experiments.
• Platinum: inert, excellent conductor, but expensive. Mentioned in some contexts.

Reactive (active) electrodes

In some cases, the electrode itself takes part in the reaction:

• Copper electrodes in copper sulfate solution: the copper anode dissolves (Cu → Cu²⁺ + 2e⁻) and copper is deposited on the cathode (Cu²⁺ + 2e⁻ → Cu). This is the basis of copper purification.
• In electroplating, the anode is made of the plating metal.

Worked exam question

Molten sodium chloride is electrolysed using carbon electrodes. (a) What is the function of the electrodes? (1) (b) Why are carbon electrodes used rather than sodium electrodes? (1) (c) Name the products at each electrode. (2)

Mark scheme

(a) To carry electric current into/out of the electrolyte / to provide a surface for the reactions [1]

(b) Carbon is inert / does not react with the electrolyte or products; sodium would react/melt [1]

(c) Cathode: sodium (metal) [1]; Anode: chlorine (gas) [1]

Common exam mistakes

• Confusing electrodes with electrolytes. The electrode is the solid conductor (usually graphite or metal). The electrolyte is the liquid that conducts (molten or dissolved ionic compound).
• Forgetting that electrode material can affect the products. With copper electrodes in copper sulfate, the anode dissolves — this does not happen with carbon electrodes.
• Not labelling which electrode is positive and which is negative in diagrams. Always label the anode (+) and cathode (-).