Question 5
What is the evidence that a chemical reaction occurs when a zinc strip is dropped into copper sulphate solution?
The right answer is the one marked above.
The blue fading and a brown powder forming. That is a change of colour — evidence that a new substance has appeared.
Gas bubbles belong to magnesium in acid, the brilliant flame to burning magnesium, and the white precipitate to the barium chloride and sodium sulphate reaction.