1. Chapter 14
Polarity

2. Alkanes
Are a simple group of hydrocarbons having the general formula CnH2n+2

4. Pentane (C5H12)

5. Hexane (C6H14)

6. Have samples of hexane (similar to gasoline), salt, methane (balloon).
Show each of these to students before asking the next question.

7. How well do they stick together?
hexane
table salt
methane

8. How well do they stick together?
hexane (liquid)
table salt (solid)
methane (gas)
table salt > hexane > methane
greatest attractive weakest attractive
forces forces

9. Table salt (NaCl)

10. Methane and Hexane are Molecular

11. They stick together through Van der Waals forces (not true bonds)

12. Larger molecules have greater Van der Waals forces
Boiling Point = –161.7°C
Boiling Point = 68.7°C

13. Rank the molecules from least to greatest Van der Waals forces?
Hexane (C6H14)
Methane (CH4)
Hydrogen (H2)
Water (H2O)
A A a a a a a a a a a a a
a a a a a a

14. A water molecule is bent

15. This makes a water molecule have different ends
This makes a water molecule have different ends. This make a water molecule _________.

16. A water molecule is polar

17. A polar molecule is called a dipole

18. Polar molecules act like little magnets
Polar molecules act like little magnets. The oppositely charged ends attract.

19. Boiling Points
68.7°C °C

20. Dipole Moment
The dipole moment is a measurement of a molecules polarity.
Example:
H2O and CO are both dipoles however water has a greater dipole moment.

21. Polarity Demo: Hexane vs. Water

22. Homework
Chapter 14 Worksheet