Which definition is correct? A. a physical change creates a new substance because bonds are broken or formed
B. a physical change can happen without changing any characteristics of the substance
C. a chemical change occurs when the substance remains the same but the shape, or other physical characteristics change
D. a chemical change produces a new substance by breaking and forming new bonds

Whereas a change that causes change in chemical composition of a substance is known as chemical change. For example, A new substance is always formed in a chemical change. Thus, we can conclude that the definition a chemical change produces a new substance by breaking and forming new bonds, is correct.

answer: the answer is b

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products