Fractional Distillation and Cracking

GOAL

By the end of today be able to explain how the boiling points of different hydrocarbons are used to separate crude oil.

VIDEO

Search Youtube for ‘Chemistry Lesson Idea: Oil Distillation’

http://www.youtube.com/watch?v=tQzgLpEWgs8 (3 min)

READ

p.193-195 Fractional Distillation and Cracking in the text book!!

ANSWER

1.  What is petroleum? (1 mark K)

2.  Which hydrocarbons usually exist as gasses? Explain why. (2 marks K)

3.  Which hydrocarbons are the most valuable? Explain why. (2 marks K)

4.  How are the various hydrocarbons separated so that they can be sold, by the length of their carbon chain? (2 marks K)

5.  Compare the length of the carbon chains and the boiling points below. (4 marks K)

Number of Carbon Atoms / Boiling Point ( C) / Hydrocarbon
Methane, ethane, propane, butane, pentane used for fuel and cooking
Gasoline
Waxes, cosmetics and polishes
Asphalt and tar for roofs and roads

6.  As the number of carbon atoms in the chain goes up, the boiling point goes ______.

This happens because as the length of the hydrocarbon molecules ______,

the number of intermolecular forces (forces between the molecules) ______as well.

Therefore, more ______is required to pull the molecules apart, meaning that ______

(4 marks K)

Fractional Distillation

7.  What process is used to efficiently separate petroleum onto its useful components?

(1 mark K)

8.  Make a list of the steps involved in fractional distillation. (5 marks K)

9.  Complete Extension Exercise 3.3 by labeling the fractionation tower (see p.195)

(9 marks K)

Cracking

10.  What is cracking? (2 marks K)

11.  Why is it an important technological process? (2 marks K)

12.  How is it done? (2 marks K)

Apply Your Knowledge

13.  A fraction of hydrocarbons with a boiling point of 10 C is collected in a fractional distillation process. Is this fraction a liquid or a gas at room temperature (20 C) ? Explain. (2 marks A)

14.  The propane in a gas barbecue tank and the wax in a candle both consist of hydrocarbons. Give the approximate boiling point of each of these substances. Use the structure of each substance to explain why the boiling point for the wax is so much higher than propane. (4 marks K)

15.  Name two substances you have used that have made from a fraction of crude oil condensed in a fractionation tower near the a)top b)middle c)bottom

(6 marks A)