Here’s another little household chemistry experiment that requires no special gear, which I am using to teach about displacement reactions and solubility at home.

Figure 1/ You just need a steel nail or screw, old tarnish copper coin(s), salt and vinegar.

Figure 2/ Mix the salt and vinegar in a container. This produces a dilute hydrochloric acid solution.
CH ₃ COOH (aq) + NaCl(aq) -> CH ₃ COONa + HCl(aq)

Put the coin in the container and swirl it around. The patina will be dissolved. (NB do not do this with valuable coins as this actually damages them a bit.) Copper (II) hydroxide is not in itself very soluble in water but copper (II) chloride is.
Cu(OH) ₂ (s) + 2HCl(aq) -> CuCl ₂ (aq) + 2H ₂ O

Figure 3/ Place the still-wet coin on some kitchen paper. Put the nail or screw in the solution, partially submerged. Leave that for a few hours.

Figure 4/ Iron is more reactive than copper, so a displacement reaction takes place: iron enters the solution and copper is deposited, coating the nail or screw. Here we see the coated screw compared to one in its original condition.
CuCl ₂ (aq) + Fe(s) -> Cu(s) + FeCl ₂ (aq)

Figure 5/ More green copper hydroxide has formed on the acid-wet coin, shown here as a stain on the kitchen paper.

very good. how permanent is the copper coating on the screw?

Very nice dv, didn’t even require electrolysis.

ChrispenEvan said:

very good. how permanent is the copper coating on the screw?

let us all know the results of your findings

ChrispenEvan said:

very good. how permanent is the copper coating on the screw?

Basically, not very. This deposition of copper is not the same process as plating: the purpose is to illustrate displacement reactions, rather than to produce durably copper coated screws for some reason.

thanks.

How different would the results be if you used a zinc screw instead of iron?

Fair question. I would guess the results would be similar as zinc, like iron, is also more reactive than copper and hydrogen.

I remember a chemistry teacher at school trying to excite us about the electrochemical series…

Reckoned he knew of bushies throwing iron bedsteads into old mine shafts which had naturally filled with copper sulphate solution. He said that with time copper would totally displace the iron.. then retrieve.

Sound legit?

Yes Ian, that is legit.

Normally: pump the CuSO4-bearing mine water out into a concrete holding tank on the surface, and throw any old iron stuff (car engines, rolls of used fencing wire or whatever, like you suggested) into the tank as well. Agitate it regularly. The Cu metal sludge on the iron objects falls to the bottom of the tank. When the water changes from bluish to greenish, most of the Cu is in the sludge, and the water contains FeSO4.

Thanks Michael.

So the bedsteads would no longer be bedstead shaped.. was mainly what I was inquiring after.

Could have worded it better.