Which is a chemical change a ice melting b ice being carved c. water boiling d water breaking down into hydrogen and oxygen

In the lock and key model, the substrate acts as the key and the enzyme as the lock. This model illustrates that the substrate has a particular shape that only permits it to fit in the enzyme, and no other substrate can bind with it. On the basis of the induced fit model when the active site on the enzymes comes into contact with the appropriate substrate the enzyme changes its configuration in order to fit with the shape of the molecule.  

Thus, the statement, which only follows the lock and key model is that the active site of the enzyme possesses a rigid composition complementary to that of the substrate.  

The statement, which only follows the induced-fit model is that the conformation of the enzyme changes when it combines with the substrate so that the active site fits with the substrate.  

The statements that follow both the models are that substrate combines with the enzyme via noncovalent interactions, and the binding of the substrate with the enzyme at the active site produces an enzyme-substrate complex.