1. Water

2. Properties of Water Polar molecule Cohesion and adhesion
High specific heat
Density – greatest at 4oC

3. Polarity of Water
In a water molecule two hydrogen atoms form single polar covalent bonds with an oxygen atom. (Gives water more structure than other liquids)
Oxygen has a partial negative charge.
Hydrogen atoms have a partial positive charge.
A water molecule is a polar molecule with opposite ends of the molecule with opposite charges.

4. Interaction Between Water Molecules
Negative Oxygen end of one water molecule is attracted to the Positive Hydrogen end of another water molecule to form a HYDROGEN BOND

5. Hydrogen Bonds Exist Between Water Molecules
Formed between a highly Electronegative atom of a polar molecule and a Hydrogen
One hydrogen bond is weak , but many hydrogen bonds are strong
Each water molecule can form hydrogen bonds with up to four neighbors.

6. Bonds to 4 molecules directly

7. 20 Second Concept Check!

8. Hydrogen Bonds Hold water molecules together
Extraordinary Properties that are a result of hydrogen bonds:
Cohesive behavior
Resists changes in temperature
High heat of vaporization (specific heat)
Expands when it freezes

9. Cohesion
Attraction between particles of the same substance ( why water is attracted to itself)
Results in Surface tension (a measure of the strength of water’s surface)
Produces a surface film on water that allows insects to walk on the surface of water 1

10. Surface tension, a measure of the force necessary to stretch or break the surface of a liquid, is related to cohesion.
Water has a greater surface tension than most other liquids because hydrogen bonds among surface water molecules resist stretching or breaking the surface.
Some animals can stand, walk, or run on water without breaking the surface.
Fig. 3.3
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

11. Cohesion = Surface Tension
Helps insects walk across water

12. 20 Second Concept Check!

13. Adhesion Attraction between two different substances.
Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton.
Capillary action -water molecules will “tow” each other along when in a thin glass tube. 1

14. Capillary action occurs when the forces binding a liquid together (cohesion and surface tension) and the forces attracting that bound liquid to another surface (adhesion) are greater than the force of gravity.
                                                                                                                                     
                                                                                                                                          
droplets.

15. Adhesion Causes Capillary Action
Which gives water the ability to “climb” structures

16. Plants rely on capillary action
Cohesion among water molecules plays a key role in the transport of water against gravity in plants
Adhesion, clinging of one substance to another, contributes too, as water adheres to the wall of the vessels.

17. Capillary Action = cohesion + adhesion

18. Adhesion Also Causes Water to …
Attach to a silken spider web
Form spheres & hold onto plant leaves

19. 30 Second Concept Check!

20. Homeostasis
Ability to maintain a steady state despite changing conditions
Water is important to this process because:
a. Makes a good insulator
b. Resists temperature change
c Coolant
d. Ice protects against temperature extremes (insulates frozen lakes) 4

21. Specific Heat is the amount of heat that must be absorbed or lost for one gram of a substance to change its temperature by 1oC.
3/4 of the earth is covered by water. The water serves as a large heat sink responsible for:
Prevention of temperature fluctuations that are outside the range suitable for life.
Coastal areas having a mild climate
A stable marine environment

22. Insulates the Earth
Water vapor forms a kind of global ‘‘blanket” which helps to keep the Earth warm.
Heat radiated from the sun warmed surface of the earth is
absorbed and held
by the vapor. 1

23. Evaporative Cooling
The cooling of a surface occurs when the liquid evaporates
This is responsible for:
Moderating earth’s climate (as mentioned before)
Stabilizes temperature in aquatic ecosystems
Preventing organisms from overheating

24. Density of Water The density of water:
Prevents water from freezing from the bottom up.
Ice forms on the surface first —the freezing of the water releases heat to the water below creating insulation.
Makes transition between seasons less abrupt.

25. Ice is about 10% less dense than water at 4oC.
When water reaches 0oC, water becomes locked into a crystalline lattice with each molecule bonded to the maximum of four partners.
As ice starts to melt, some of the hydrogen bonds break and some water molecules can slip closer together than they can while in the ice state.
Ice is about 10% less dense than water at 4oC.
Fig. 3.5
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

26. Water is Less Dense as a Solid
Which is ice and which is water? 1

27. Water is Less Dense as a Solid
Ice 1

28. 30 Second Concept Check!

29. Let’s recap… Your answer to each of the following will be either:
Polarity
Cohesion
Adhesion
Specific Heat
Density
Hold up either 1, 2, 3, 4 or 5 to show your response

30. Water molecules creating a hydrogen bond with each other!
Polarity
Cohesion
Adhesion
Specific Heat
Density
Water molecules creating a hydrogen bond with each other!

31. Temperature of water rises and falls very slowly
Polarity
Cohesion
Adhesion
Specific Heat
Density
Temperature of water rises and falls very slowly

32. Hydrogen molecule is slightly positive
Polarity
Cohesion
Adhesion
Specific Heat
Density
Hydrogen molecule is slightly positive

33. Capillary action is brought on by this!
Polarity
Cohesion
Adhesion
Specific Heat
Density
Capillary action is brought on by this!

34. Leads to surface tension of water
Polarity
Cohesion
Adhesion
Specific Heat
Density
Leads to surface tension of water

35. Water freezes from the surface on down
Polarity
Cohesion
Adhesion
Specific Heat
Density
Water freezes from the surface on down

36. Oxygen molecule is slightly negative
Polarity
Cohesion
Adhesion
Specific Heat
Density
Oxygen molecule is slightly negative

37. Plants rely on these TWO properties of water to transport water within
Polarity
Cohesion
Adhesion
Specific Heat
Density
Plants rely on these TWO properties of water to transport water within

38. Bugs can walk on water due to this property!
Polarity
Cohesion
Adhesion
Specific Heat
Density
Bugs can walk on water due to this property!

39. This property allows our bodies to maintain homeostasis
Polarity
Cohesion
Adhesion
Specific Heat
Density
This property allows our bodies to maintain homeostasis

40. This property was evident when trying to float the needle on water
Polarity
Cohesion
Adhesion
Specific Heat
Density
This property was evident when trying to float the needle on water

41. This property was evident when dropping water onto a penny
Polarity
Cohesion
Adhesion
Specific Heat
Density
This property was evident when dropping water onto a penny

42. This property was evident when using the tube to “draw” up water
Polarity
Cohesion
Adhesion
Specific Heat
Density
This property was evident when using the tube to “draw” up water

43. Polarity
Cohesion
Adhesion
Specific Heat
Density
This property was evident when freezing the water to see if it froze top/bottom first.

44. Polarity
Cohesion
Adhesion
Specific Heat
Density
This property was evident when freezing the water to see if it froze top/bottom first.

45. These TWO properties were evident when transporting water on a string!
Polarity
Cohesion
Adhesion
Specific Heat
Density
These TWO properties were evident when transporting water on a string!

46. Polarity
Cohesion
Adhesion
Specific Heat
Density
This property was evident when dropping substances onto pepper in water

47. This property was evident when heating water versus oil.
Polarity
Cohesion
Adhesion
Specific Heat
Density
This property was evident when heating water versus oil.

48. How did you do?? Hold your cards up and rate yourself a 1-5…
1 = I didn’t learn anything … boo! 
5 = I can repeat all of this information back to you already! Bam!