Question 1

A. A charcoal briquette burns

Exothermic. As it burns, heat is released.

B. Water evaporates from your skin

Endothermic. For evaporation to occur, water absorbs the necessary heat from the surroundings

C. Ice melts

Endothermic. Melting occurs when ice absorbs heat from the environment

Question 2

Q: Chemical explosions are very exothermic reactions. Describe the relative bond strengths in the reactants and products that would make for a good explosion

A: The bond energy of the product must be larger than the bond energy of the reactant to produce a very exothermic reaction. This is to form a very large net negative energy

Question 3

Q: How might you explain the difference between temperature and heat to a friend? Use some practical, everyday examples?

A: Let’s use hot water as an example. It would be preferable to have a single drop of water scald you as compared to an entire jug of water, even though the temperature remains constant. This is because temperature is just a measure of heat energy. A larger volume of hot water means that there is more heat and thus your burn will be more severe.

Question 4

A. The knocking characteristics of this gasoline?

An octane rating of 98 implies that the mixture contains 98% isooctane and 2% n-heptane. This means that it is more resistant to knocking than octane with lower rating.

B. Whether the fuel oxygenates

The octane rating does not reveal whether the fuel contains oxygenates. This information should be found around the pumps on labels.