Electroplating
A current turns metal ions into a metal coat
1. Alloys and their types
2. A copper coat from a solution
An iron key hangs in a solution of copper ions. A battery runs for ten minutes. The key comes out copper-coloured.
Pick the right answer
Predict: where did the copper coat come from?
- A. Copper ions in the solution became copper metal on the key
- B. The iron of the key changed into copper
- C. Copper dust in the liquid stuck to the key
الشرح
The copper coat came from the copper ions in the solution: the current drove them to the key, where they gained electrons and became copper metal.
3. What electroplating is
Electroplating
Coating an object with a thin metal layer by passing a current through a solution of that metal's ions.
The object is joined to the negative terminal. The positive metal ions are attracted to it.
4. At the cathode
Cathode
The electrode where reduction (gain of electrons) happens, in every cell. In electroplating, it is the plate joined to the negative terminal: the object to be coated.
Time (stage) 1
Cu²⁺ + 2e- → Cu
Electrons reach the key from the battery. Each copper ion gains two and becomes a copper atom. The coat grows.
5. Coat or no coat?
The coat is made of the metal whose ions are in the solution.
Sort into groups
Does the object get a metal coat?
Object joined to −, in a solution of nickel ionsObject joined to +, in a solution of nickel ionsObject joined to −, in a sugar solutionObject joined to −, in a solution of zinc ions
6. Check yourself
Pick the right answer
You want to coat a spoon with silver. Which setup works?
- A. Spoon joined to −, in a solution of silver ions
- B. Spoon joined to +, in a solution of silver ions
- C. Spoon joined to −, in a solution of copper ions
- D. Spoon joined to −, in a sugar solution
الشرح
To coat a spoon with silver, the spoon is joined to − and dipped in a solution of silver ions: the positive silver ions move to the spoon, gain electrons and deposit as silver.
Fill in the blanks
In electroplating, the object to be coated is joined to the _____ terminal of the battery.
الشرح
The object to be coated is joined to the negative terminal. The metal ions are positive, so they are attracted to it and deposit on it as metal.
True or false?
In electroplating, the metal ions lose electrons at the object.
الشرح
At the object, the metal ions gain electrons: Cu²⁺ gains 2 electrons and becomes a neutral Cu atom.
7. Summary
- Electroplating: a current through a solution of metal ions coats an object with that metal.
- In electroplating, the object is the cathode: it is joined to the negative terminal.
- At the cathode, metal ions gain electrons (reduction) and become atoms.
Next: with ions of two metals, both deposit at once. The book prepares alloys this way.
Can you explain why the object goes on the negative terminal?
Reveal
The metal ions are positive, so they are attracted to the negative terminal and pushed away from the positive one. At the object they gain electrons and become the metal coat.