As a train approaches the sound waves are crowded together (compressed) and produce a higher pitch. As the train moves away the sound waves move farther apart (elongate) and produce a lower pitch. What term is used to describe this effect?

Select all the correct answers. which changes will increase the rate of reaction during combustion? decreasing the area of contact between the reactants adding more oxygen to the reaction removing heat from the reaction changing the reactants from solid form to powdered form lowering the exposure of the reactants to air