Your answer is D. 8
16 = 2^4
72 = 2^3*3^2
So you'll choose 2^3 = 8
Physical, since you are physically changing its appearance
Something that melts, something that changes shapes (for instance, play dough being squished), something that boils, something being mixed or dissolved (but only if it doesn't chemically react), etc. A physical change is a change of state of matter.
Reactants are what is changed in the chemical reaction. They go before the arrow when you wrote the equation. Products are what is formed when the chemical reaction occurs. Products always contain the same elements as the reactants, but they might be rearranged because of the reaction. In this picture, you can see that the reactants go before the arrow, and the products go after.