a. Exothermic – Heat Energy is release so that bonds can be formed.
b. Endothermic
c. Endothermic
Heat energy is absorbed in both B & C so that hydrogen bonds can be broken.

The relative bond strengths in the reactants and products needs to be weak so that bonds can be broken easily. For example, elements in gaseous state generally have weaken bonds thus it would be idea for a good explosion.

Heat is energy that flows from a hotter to a colder object while temperature determines the direction of heat flow.Heat is a consequence of motion at the molecular level; temperature is a measure of the average speed of that motion.The heat of an object contains is the amount of its thermal energy, measured in joules or J. On the other hand, the temperature of an object is to do with how hot or cold it is, measured in degrees Celsius. Note that the unit of temperature is written as °C.

For example, to boil water we must increase its temperature to 100°C. It takes longer to boil a large beaker of water than a small beaker because the large beaker contains more water and needs more thermal energy to reach 100°C.

a. Octane rating measures the ability of gasoline to burn smoothly without knocking. Octane number of 92 means a knocking characteristic of 98% isooctane and 2% heptanea.

b. The rating is just an indication of the composition of fuel. It does not give an accurate description on whether oxygenates are present. Thus, further analysis is required to determine its oxygenates level.