Question

question 7 (1 point)
the energy change for a chemical reaction that involves the formation of a
compound from its elements and that is determined experimentally under standard
conditions is known as
heat of combustion
standard heat of formation
combustion
exothermic reaction
question 8 (1 point)
which statement accurately describes the energy changes within the cylinders of a
snowmobile engine as a result of the combustion of fuel?
chemical energy decreases and the total kinetic energy of the molecules
decreases.
chemical energy decreases and the total kinetic energy of the molecules
increases.
chemical energy increases and the total kinetic energy of the molecules
decreases.
chemical energy increases and the total kinetic energy of the molecules
increases.

Explanation:

Question 7: The definition matches the standard heat of formation, which is the enthalpy change when a compound forms from its elements under standard conditions.
Question 8: Fuel combustion is an exothermic reaction: chemical energy stored in fuel bonds is released, so chemical energy decreases. This energy is converted to thermal energy, increasing molecular motion and thus total kinetic energy of molecules.

Answer:

Question 7: B. standard heat of formation
Question 8: B. Chemical energy decreases and the total kinetic energy of the molecules increases.