CM8001

a. exothermic reaction – charcoal gives off heat when burned.
b. endothermic reaction – water takes in heat to evaporate, from liquid to gaseous state.
c. endothermic reaction – ice absorbs heat to melt from solid to liquid state.

The bonds within the reactants are weak in a highly exothermic reaction while those within the products are strong. The energy needed to break the bonds within the reactants is small as less energy is needed to overcome weak bonds. This thus leads to negative net energy change.

Temperature – the average measure of heat energy with respect to movement of molecules. Temperature determines the direction of heat flow.
Heat – energy flowing from a hotter to colder object

eg. you can set the temperature of a room to hotter or colder.
when you touch a hot vessel, you can feel the heat.

a. As the octane reading is 98, it has the same knocking characteristics as a mixture that contains 98% octane, therefore it is more resistant to knocking than gasoline with lower octane reading.

b. The octane rating does not say anything about whether the fuel contains oxygenates. Other labels provide that information.