CM8001

a. Exothermic as heat is given out as it burns.
b. Endothermic as water gains energy to change phase from liquid to vapour.
c. Endothermic as it takes in energy for it to melt to overcome the intermolecular forces of attraction between the particles to change into liquid state.

Enthalpy change of reaction = sum of bond strength of bonds broken – sum of bond strength of bonds formed
A good explosion requires a highly exothermic reaction. Thus, the bonds of reactants should be weak and the relative bond strength of the product should be high.

Heat is the total energy of molecular motion in a substance but temperature is a measure of the average energy of molecular motion in a substance. Temperature does not depend on the size and type of the object, but heat does.

For example, the temperature of a small cup of water might be the same as the temperature of a large tub of water, but the tub of water has more heat because it has more water and thus more heat/thermal energy

a. As the reference standard for octane rating is 100, which refers to a gasoline containing pure iso-octane, the gasoline with 98 octane rating has the same knocking characteristics as a mixture of 98% iso-octane and 2% heptane.

b. Oxygenates are chemical compounds that contain oxygen but the octane rating only reflects the knocking characteristics of gasoline but not the chemical formula of it. So the octane rating does not tell us if the fuel contains oxygenates.