Unit 4: Energy from Combustion APPLICATION EXERCISE

 

Question 1

a: exothermic. We feel hot when we put our hands near the burning charcoal

b: endothermic. We feel a cooling sensation when the water evaporates from our skin.

c: endothermic. Our hands feel cold when we put it near an ice cube.

Question 2

Bond energy of products should be much lesser than the reactants, in order to release a large amount of energy.

change in enthalpy = bond energy of products – bond energy of reactants

Question 3

Temperature is really just a measure of the vibrational energy of the particles. It can be directly measured using the Fahrenheit, Celsius and Kelvin scale.

For heat, it is a measure of the difference in temperature. For example, we submerge our right hand into ice water and left hand into hot water. Then remove both hands from the water and submerge both in lukewarm water. The right hand will feel cold while the left hand will feel hot. This is due to the difference in temperature.

Question 4

a: An octane number of 98 means a knocking characteristics of 98% isooctane and 2% heptane.

b: Fuels containing oxygenates would usually have an octane rating of higher than 100. Typically, fuels of octane rating of 98 to 100 do not contain oxygenates. Thus, the fuel does not contain oxygenates.