Evidence that a chemical change has occurred includes a .

a. change in state
b. change in size
c. change in shape
d. change in color

An oven's high temperature speeds up chemical reactions because heat .

a. lowers the activation energy
b. activates catalysts
c. makes more molecules collide with each other
d. reduces the particle size of the reactants

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .

Sorry i dont understand the question can you rephase it?

B? i feel like this is a trick