Answer:
reacts in air to form a green layer
Step-by-step explanation:
Properties of substances can be physical or chemical. A physical property is that which does not affect the chemical composition of the substance(s) involved e.g melting point, boiling point, color, state of matter as depicted for copper (Cu) in this question.
On the other hand, chemical property of a substance are those properties that alters or affects the chemical composition of the substance. In other words, they are features that can be observed after the substance has undergone a chemical reaction. In this question, COPPER REACTING IN AIR TO FORM A GREEN LAYER IS A TYPE OF CHEMICAL PROPERTY because a chemical reaction has occured with the evidence of the green layer formation.