Copper-Plating

Electrolysis

Electrolysis

Electrolysis is a process in which an electric current is passed through a liquid, causing a chemical reaction to take place. The liquid used is called the electrolyte. The wires or plates where the current enters or leaves the liquid are called electrodes. The electroysis of metallic solutions is useful in putting metal coatings on objects. If you have a look at a car bumper, you will notice that it has a nice, smooth, metallic appearance. This is because car bumpers are coated with the metal, nickel, in a process called electroplating. This helps to stop the metal underneath from rusting. The same method is used to coat cutlery with silver. This is called silver plating. Michael Faraday discovered the first law of electrolysis. The process is also used to purify metals like aluminium.

Copper-Plating

Copper-Plating

01. For this project you will need a glass jar, a copper coin, a paper clip, two batteries, insulated wire and water. Pour the water into the jar. Place the batteries together with unlike terminals adjacent. Connect wires to the terminals. Attach the copper coin to the wire from the a positive terminal of the battery. The paper clip must be attached to the wire from the negative terminal. Use plasticine. Do not allow the metal objects to touch in the solution. You could even tape each wire to the side of the jar so that they are suspended.

02. Observe closely what happens. Can you see bubbles? Leave them for a few minutes, then remove. Observe any colour changes. Replace them for a while. Are there any further changes?

Why It Works

copper coin

The copper coin is connected to the positive terminal of the battery - the current enters here. The other, the paper clip, is joined to the negative terminal - the current leaves here. As the current flows through the water from the positive electrode (anode) to the negative electrode (cathode), the copper is carried from the coin to the clip.

Copper-Plating 01

Bright Ideas
H Repeat the project using salt dissolved in vinegar instead of the water. What difference do you notice - if any? What do you observe about the appearance of the paper clip? Maybe your school has scales that can weigh very small objects? If the coin and the paper clip are weighed before immersion in the liquid and their weight recorded, you can check whether electro-plating has really taken place. After carrying out the project weigh them both again. Now replace the battery with a more powerful one, or add a second battery into a parallel circuit, to increase the 'push' of the current passing through the liquid. Weigh the coin and paper clip a second time. If the weight of the paper clip has increased further, then you have proved the first law of electrolysis -the size of the charge passed through the liquid determines the amount of copper freed.