CM8001

a. Exothermic. A charcoal briquette releases heat as it burns due to the bond formation.
b. Endothermic. Water absorbs the heat necessary for hydrogen bonding for evaporation from your skin, and thus, makes the skin feel cooler.
c. Endothermic. Ice absorbs the necessary heat from the environment to break the hydrogen bond in order to melt into a liquid.

For a good explosion to occur, it has to be an exothermic reaction. Hence, the bond strength of the products has to be much higher than that of the reactants. Thus, this would result in a higher negative net energy change, leading to a good explosion.
For instance in methane explosion:
CH4 +2O2 → CO2 + 2H2O
Given that the C-H bond: 416 kJ/mol; O=O bond: 498 kJ/mol; C=O bond: 803 kJ/mol; O-H bond: 467 kJ/mol. Hence, the bond formation energy (products) is much larger that the bond breaking energy (reactants).
Moreover, for a good explosion, the product would be in a gas state.

Temperature is not a form of energy as it measures the average speed of the direction of heat flow. Meanwhile, heat is a form of energy that transfers from hotter region to colder region.
For example, a cup of water has the same temperature as a tub of water. However, the tub of water contains more heat than the cup of water. This is because the tub of water has a larger volume, thus resulting in a higher heat content as compared to the cup of water.

The octane rating is the measure of the ability of gasoline to burn smoothly without knocking.
a. The octane rating of 98 means that the premium gasoline has a knocking characteristic of 98% isooctane and 2% heptane.
b. The presence of oxygenates in the premium gasoline cannot be determined from the octane rating. Other labels on the packaging should reveal this information.