Which of the following changes are classed as a chemical change?
a) The fluorescent green solution formed when brick red ammonium dichromate is placed in water
b) When heated over a bunsen, white zinc oxide turns yellow
c) The blue solution that forms when sulphuric acid is added to copper oxide
d) The purple solution that forms when potassium permanganate is added to water
Dissolution of copper oxide in sulfuric acid is chemical process:
CuO + H2SO4 --> CuSO4 + H2O
During this reaction the copper oxide turns to copper sulfate. So, the correct option is c.