Question

9) From the list below, identify which situation(s) contain chemical changes. I) A pot of water is being heated on a stove. Bubbles form and condensation appears on the lid of the pot. II) A translucent, blue copper (II) sulfate solution is mixed with another solution and changes to a translucent lighter blue color. III) Ammonium nitrate solid dissolves in water and feels very cold. IV) Red and blue paint are mixed together and the color purple appears. A) I and II B) III only C) II, III and IV D) I, II and III

Answer 1

The correct answer is B) III Only

Answer 2

Your instructor is probably expecting the answer B) III only.

III) The evolution or absorption of heat is evidence of a chemical change.

I) Boiling water and IV) mixing paint are physical changes.

II) A change in colour on mixing is usually an indication of a reaction (but not when mixing paint). However, in this case, the lighter blue colour might have happened simply because you are diluting the solution. You would have to do an experiment which is correct.