CM8001

a) Exothermic – the charcoal burns the skin and gives out heat

b) Endothermic – the skin feels cooler when water (like sweat) evaporates from the skin

c) Endothermic – the ice takes in heat to become water, which is an endothermic process

The reactants should have very weak bonds and the products should have very strong bonds. The greater the energy difference between the products and reactants, the more vigorous the reaction as more energy is released.

Heat is the transfer of energy from a hotter object to a cooler object, while temperature is the absolute amount of energy possessed by the object.

For example, heat is the steam given off by a cooking pot, which can cook an egg, but temperature is a measurement of how hot the steam is.

a) An octane rating of 98 means that the gasoline has a knocking characteristic of 98% isooctane and 2% heptane. Isooctane has a lower boiling point than heptane and has a lower tendency to cause “knocking” in the engine. Therefore, gasoline with an octane rating of 98 would suggest a low tendency to cause knocking, and burns more smoothly.

b) The octane rating gives no clear indication of whether the fuel contains oxygenates. Examples of oxygenates include, MTBE, ETBE, methanol and ethanol. However, oxygenates enhance the octane number of the gasoline, assists combustion, reduces CO emissions and reduces knocking. Therefore, a high octane rating of 98 suggests that the gasoline does contain oxygenates, producing premium gasoline.