The statement "In a chemical change the appearance changes but the substance does not" is not accurate. In a chemical change, both the appearance of the substance and the substance itself change. During a chemical change, reactants undergo a transformation to form new products, which have different chemical properties and often different physical properties as well.
For example, when iron rusts, it reacts with oxygen and moisture in the air to form iron oxide, a different substance with distinct characteristics. The change in color and texture is an observable indication of this chemical reaction.
In contrast, a physical change involves a change in appearance without altering the chemical identity of the substance. An example of a physical change is melting ice into water; the substance (H2O) remains the same, even though its state (solid to liquid) has changed.