Answers section

Questions 3.1.2(a)

In ordinary language, what does it mean to crack something?
Why is it sometimes necessary to crack a substance?
How does the burning of butane (a smaller alkane) compare with the burning of kerosene (a mixture of longer alkanes)? Refer to Figure 3.1(a).
Large objects such as rocks can be cracked using a sledge hammer or power grinder. Suggest how the invisible alkane molecules may be cracked (Hint: Kinetic property, movement and collision)

Answers to Questions 3.1.2(a)

To crack is to break something into smaller particles.
Smaller molecules can be used as building blocks or units for other substances.
Butane, a smaller alkane, burns more efficiently with a blue hot flame than kerosene, which is a mixture of molecules of longer chains.
Heating to high temperatures: This causes long (large) molecules to move faster (and vibrate faster), breaking down upon collisions. Increasing pressure: This reduces spaces between molecules; so they collide faster (and break faster).