1. Water Properties: Lecture

2. Fun for recreation

3. Kid tested, Mother approved

4. Goals:
Understand that water’s unique properties are the result of hydrogen bonding.
Identify and describe important properties that make water critical for life on Earth.

5. Water Lab: Reflection
What water phenomena (behaviors) did you observe in the lab?
Water forms a “dome” shape.
Soap causes the dome to collapse.
Water doesn’t stick well to wax paper.
It resists flowing over the lip of a beaker.
Pepper bunches together and sticks to the water’s surface.
Pepper “clusters” spread out quickly when soap is added.

6. Water Properties: Topics
Water is sticky.
Water has a high heat capacity.
Water is a solvent.
Water is a liquid at room temperature.
Water is a viscous substance.

7. Property #1: Water is “sticky”
The "stickiness" of water molecules to each other is called cohesion.
The "stickiness" of water molecules to other molecules is called adhesion.

8. Water Strider

9. Try it!
Using the tweezers and a Petri Dish with water, balance a paper clip on the surface of the water.

10. Property #1: Water is “sticky”
Surface Tension: Water’s ability to resist an object penetrating its surface.
This is the product of cohesion.

11. Hydrogen Bonding:
Because of hydrogen bonds, both adhesion and cohesion (and surface tension) result.
These bonds form between oxygen and hydrogen and make it difficult to separate neighboring water molecules.
[Copy the diagram from next slide].

14. Water Properties: Topics
Water is sticky.
Water has a high heat capacity.
Water is a solvent.
Water is a liquid at room temperature.
Water is a viscous substance.

15. Property #2: Water has a high “Heat Capacity”:
Water absorbs a large amount of heat energy before it increases its temperature 1 ° Celsius.
It must lose a large amount of temperature, too, for the temperature to drop by 1 ° Celsius.
Effect: The ocean doesn’t get too hot or too cold and organisms can better adapt to their environment.

16. Heat Capacity Graph D E C B A

17. Heat Capacity Graph A E D C B ***
A: Water is frozen. Molecules packed less densely than solid.*** Heat energy is used to weaken hydrogen bonds. A E D C B
END 3/14/18 Prompted to summarize relationship in graph
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18. Heat Capacity Graph A E D C B ***
B: Water is “sliquid”. Molecules packed more densely than vapor.*** Heat energy is used to more fully weaken hydrogen bonds  liquid. A E D C B
***

19. Heat Capacity Graph A E D C B ***
C: Water is liquid. Molecules packed much more densely than vapor. Heat energy is used to weaken hydrogen bonds further. A E D C B
***

20. Heat Capacity Graph A E D C B ***
D: Water is a mixture of vapor and liquid. Molecules packed very loosely. Heat energy is used to weaken remaining hydrogen bonds. A E D C B
***

21. Heat Capacity Graph A E D C B ***
E: Water is fully vapor. Molecules have little to no H-bonding. A E D C B
***

22. Water Properties: Topics
Water is sticky.
Water has a high heat capacity.
Water is a solvent.
Water is a liquid at room temperature.
Water is a viscous substance.

23. What’s the best way to start cleaning this mess?

24. Property #3: Water is a “solvent”:
By volume, water is the most abundant chemical ingredient of the ocean.
All matter in the ocean is suspended by water.
Without it, no chemical reactions would ever occur (at normal rates) because all chemicals must be able to move around to collide with and interact with each other.

25. Water wiggles in there and breaks things up.

26. Property #3:
Therefore, the chemical needs of living organisms would be impossible.
Input: obtaining nutrients, gases
Processing: metabolizing food and extracting energy.
Output: releasing waste products

27. Water is involved in each process.

28. Water Properties: Topics
Water is sticky.
Water has a high heat capacity.
Water is a solvent.
Water is a liquid at room temperature.
Water is a viscous substance.

29. Property #4: Water is a liquid at room temperature:
The most important trait that results from hydrogen bonding.
Without these connections, water would be a gas at room temperature.
Without them, Earth would be a steamy planet, perhaps more like Venus.

30. Water boils at highest temperature because it contains H-bonds.
Usually…
smaller molecules boil more quickly
Larger molecules boil more slowly
But…
Water doesn’t want to leave it’s friends; it takes more energy to convince them

31. Water boils at highest temperature because it contains H-bonds.
Usually…
smaller molecules boil more quickly
Larger molecules boil more slowly
But…
Water doesn’t want to leave it’s friends; it takes more energy to convince them

32. Why does ice float?

33. Why does anything float?
A floating object displaces (moves aside) a weight of fluid equal to its own weight.

34. Why does ice float?
Ice floats because it is about 9% less dense than liquid water.
The ice displaces the same (or greater) volume of water, so ice floats to the top.

35. Why does ice float?
As water freezes into ice, it actually becomes less dense; the opposite of nearly all substances.
Below 4°C, the hydrogen bonds adjust (push apart) near neighboring negatively charged oxygen atoms.
This produces a “crystal lattice”, (ice).

36. Density: watersolid < waterliquid

37. Water reaches Densitymax @ 4°C (40°F).

38. Water Properties: Topics
Water is sticky.
Water has a high heat capacity.
Water is a solvent.
Water is a liquid at room temperature.
Water is a viscous substance.

39. Property #5: Water is a “viscous” substance.
Its tendency to resist flow (like syrup) is the result of hydrogen bonds preventing adjacent water molecules from moving apart.

40. Temp. v Viscosity
For each drop of 20° Celsius, the viscosity increases by 60%.
Cold water moves more slowly than warm water.

41. Property #5: So what?
As a result, drifting marine organisms (like plankton) can float more easily in cold water and save more of their energy.
However, swimming organisms must work harder to “plow” through water.

42. Water Properties Exit Task
Write a brief reflection of these notes in light of the two goals presented for these notes.
Understand that water’s unique properties are the result of hydrogen bonding.
Identify and describe important properties that make water critical for life on Earth.
Minimum of two paragraphs
Refer to all five properties that water possesses.

43. Practice Questions
Water Properties

44. Practice Question #1
Cohesion describes the situation where _______”sticks” to_______.
Water, water
Water, substances other than water.
Glass, Water
A and C

45. Practice Question #2
Adhesion describes the situation where ______”sticks” to _______.
Water, water
Water, substances other than water.
Glass, Water
B and C

46. Practice Question #3
When droplets of water form on a blade of grass, what causes the droplet to be rounded (sphere shaped)?
Cohesion
Adhesion
Solvency
Heat Capacity

47. Practice Question #4
Compared to other liquids containing hydrogen, water______.
Boils at a lower temperature
Boils at the same temperature
Boils at a higher temperature

48. Practice Question #5
Smaller invertebrate animals are able to float and drift easily because water has a low viscosity.
True
False

49. Practice Question #6
Water molecules are attracted to each other because _________.
Positively charged oxygen atoms in adjacent water molecules are drawn together
Negatively charged oxygen atoms in adjacent water molecules are drawn together
Positively charged hydrogen and negatively charged oxygen atoms in adjacent water molecules are attracted to each other
Negatively charged hydrogen and positively charged oxygen atoms in adjacent water molecules are attracted to each other.

50. Practice Question #7
Water is a solvent. Which of the following statements does not relate to this property?
The rate of chemical reactions is increased
The rate of chemical reactions is decreased
Gases and nutrients are obtained
Food is metabolized and energy is extracted from it
Waste products are released

51. Practice Question #8
Explain the relationship shown in this graph, including the five line segments.

52. Practice Question #9
Water is “sticky” for what reason? Explain the chemical property of the water molecule in your answer. Consider the picture below as you prepare your answer.

53. Practice Question #10 Compared with other molecules, water ___.
Freezes at a higher temperature
Freezes at a lower temperature
There is no difference in the freezing temperature