Question

why does the colour of copper sulphate solution change when an iron nail is dipped in it​

Answer 1

because high reactive metal can displace the respective matter as it is a property shown in the displacement reaction so that's why when it displays it's also changes the colour

Answer 2

Answer:

When an iron nail dipped in the copper sulphate solution than iron displaces copper from the copper sulphate because iron is more reactive than copper. Therefore the colour of the copper sulphate solution changes.

Hope it helps!