It’s week 5, and we got our group topic today: Energy From Combustion.
This week, we covered Unit 4: Energy from Combustion.
Here are our answers for AE 3.
Question 1
From personal experience, state whether these processes are endothermic or exothermic. Give a reason for each.
a. A charcoal briquette burns
It is exothermic because heat is released by the charcoal briquette. We are able to feel the heat from the fire.
b. Water evaporates from your skin
It is endothermic because heat is gained by the water.
c. Ice melts
It is endothermic because heat is gained by the water to be gas.
Question 2
Chemical explosions are very exothermic reactions. Describe the relative bond strengths in the reactants and products that would make for a good explosion.
The total bond strength of the product has to be stronger than that of the reactant such that more energy is released during the bond formation than is absorbed during the breaking of bond in reactants.
Question 3
How might you explain the difference between temperature and heat to a friend? Use some practical, everyday examples.
Heat is a form of energy while temperature is a measure of heat. For example, when boiling water, heat is transferred to water to raise its temperature to its boiling point.
Also, heat is both a noun and a verb while temperature is only a noun.
Question 4
A premium gasoline available at most stations has an octane rating of 98. What does this tell you about:
a) the knocking characteristics of this gasoline?
A gasoline’s octane rating is a measure of the gasoline’s resistance to causing knocking in a vehicle’s engine. The higher the rating, the more resistant it is to knocking in a vehicle’s engine and also the more branched the molecule.
An octane rating of 98 shows that there will be very little knocking.
b) whether the fuel contains oxegenates?
The octane rating tells us nothing about whether or not the fuel contains oxegenates.