1. Chapter 14 Polarity

2. Alkanes Are a simple group of hydrocarbons having the general formula C n H 2n+2

4. Pentane (C 5 H 12 )

5. Hexane (C 6 H 14 )

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 table salt > hexane > methane greatest attractiveweakest attractiveforces

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

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 (C 6 H 14 ) Methane (CH 4 ) Hydrogen (H 2 ) Water (H 2 O) A A a a a a a a a a a a a a a a a a a

14. Did you get this order? Hydrogen(H 2 ) < Water(H 2 O) < Methane(CH 4 ) < Hexane(C 6 H 14 ) A A a a a a a a a a a a a a a a a a a

15. It’s Wrong Hydrogen(H 2 ) < Water(H 2 O) < Methane(CH 4 ) < Hexane(C 6 H 14 ) A A a a a a a a a a a a a a a a a a a

16. The state of matter determines the attractive force? Methane (CH 4 ) and Hydrogen (H 2 ) are gases Water (H 2 O) and Hexane (C 6 H 14 ) are liquids A A a a a a a a a a a a a a a a a a a

17. The state of matter determines the attractive force? ? H 2 < CH 4 < H 2 O < C 6 H 14 ? gases liquids A A a a a a a a a a a a a a a a a a a

18. Boiling points can confirm your answers.

19. Boiling Points Hydrogen has a boiling point -252.87 ºC. Methane has a of −161 °C

20. Boiling Points 68.7°C 100°C

21. Rank the molecules from least to greatest Van der Waals forces? Hydrogen (H 2 ) <Methane (CH 4 ) < Hexane (C 6 H 14 ) < Water (H 2 O) A A a a a a a a a a a a a a a a a a a

22. What is the shape of a water molecule?

23. A water molecule is bent. It therefore lacks symmetry.

24. This makes a water molecule have different ends. This makes a water molecule _____.

25. This makes a water molecule have different ends. This makes a water molecule polar.

26. A water molecule is polar because it has oppositely charged ends. AAAAAAAAAAAAAAAAAAAAAAAAAA

27. A polar molecule is called a dipole AAAAAAAAAAAAAAAAAAAAAAAAAA

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

29. Van der Waals Forces are based on: 1.Size 2.Polarity

30. Lucky for us water is polar Hydrogen has a boiling point -252.87 ºC. Methane has a of −161 °C

31. Dipole Moment The dipole moment is a measurement of a molecules polarity. Example: H 2 O and CO are both dipoles however water has a greater dipole moment.

32. Polarity Demo: Hexane vs. Water

33. Homework Chapter 14 Worksheet