How can an enzymes shape be changed?

If the shape of an enzyme is changed, the identification between the enzyme and the substance this enzyme works on will not happen.

The enzyme becomes useless. Only a specific substrate will bind to an enzyme and if the substrate is changed, a different enzyme must be made to bind it.

Because it alters the enzymes active site, which makes it unable to catalyze the reaction it's intended to.

high temperatures or a certain amount of pH

In organic chemistry, chemicals have to have the right shapes so that they will fit together, in order to react in the way that is needed for whatever biological process which that chemical...