Water Water Everywherex - cmbiology

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14 Δεκ 2013 (πριν από 4 χρόνια και 18 μέρες)

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Water Water Everywhere…


Water is everywhere. It's in the air we breathe. It's in our sink faucets, and it's in every cell of our
body. Water is an unusual substance with special properties.


Can you answer these questions?

1.How

does water rise from the roots of a redwood tree to the very top?

2.How do insects walk on water?

3.Why does ice float rather than sink?

4.Why do
some materials dissolve in water while others do not?


5.How would life in a lake be affected if ice sank
and lakes froze from the bottom up?



Objectives
:

Once you have completed this exercise you should be able to:

1.

Describe the
polarity

of a water molecule and explain how that
polarity

affects the
properties of water.

2.

Explain why water forms beads on a wax
ed car but not on an unwaxed car.

3.

Explain why two wet cereal bowls stacked together are hard to pull apart.

4.

Explain why water climbs a paper strip.

5.

Explain why oil and water don't mix.

6.

Predict whether a substance, based on its
hydrophilic

and/or
hydropho
bic

properties,
will dissolve into water or oil.


Materials
: safety goggles, wax paper square, paper towel square
, pipette, 50 mL beaker
of water,


pepper, dish soap, 2 glass microscope slides
, toothpick
, etc.


Protocol
:


Part A

1.


Put on safety goggles.

2.

Place one drop of water onto the square of wax paper.

3.

Pick up the corners of the wax paper and describe the behavior of the water.

4.

Insert a toothpick into the water drop. Can you drag the water drop around with the toothpick?
Why
do you think this is so? (Think about the properties of water.)

5.

Attempt to break the drop of water into smaller droplets with the toothpick. Would you describe
this as being easier or harder than you thought?

6.

Repeat steps 2
-
5 but place the drop of water
onto your desk top instead of wax paper. Compare
the behavior of the water on this surface.

7.

Which surface, your desk top or the wax paper is hydrophilic (polar) and which surface is
hydrophobic (nonpolar)? How do you know?

8.

On your lab sheet, summarize wh
at you learned from Part A.


Part B

9.

Place one glass microscope slide directly on top of the other.

10.

Attempt to lift the top slide off of the bottom slide by placing your thumb and index finger on
opposite sides of the top glass slide.

11.

On a scale of 1
-
5 wit
h 5 being extremely difficult, rate how hard it was to lift the slide.

12.

Next, place one glass slide on your desk top and using the pipette, place three drops of water on
the slide. Place one drop at each end and another in the center of the slide.

13.

Place an
other glass slide directly on top of the wet slide.

14.

Repeat step
s 9
-
10.

15.

What property/properties of water caused this to happen?

16.

On your lab sheet, summarize what you learned from Part B.


Part C

17.

Put a drop of water on your desk top.

18.

Place the corner of
a square of paper towel into the water.

19.

Describe what happens.

20.

What property/properties of water are at work?

21.

On your lab sheet, summarize what you learned from Part C.


Part D

22.

Sprinkle one small shake of pepper onto the surface of the water in your
beaker.

23.

Does the pepper sink or float?

24.

Now place one drop of liquid soap onto the surface of the water and describes what happens to
the pepper.

25.

Explain what happened and why. (Hint: what do you believe is true about soap? Is it
hydrophobic or hydrophilic
?)

26.

On your lab sheet, summarize what you learned from Part D.


CLEAN
-
UP PROCEDURES



Throw the paper towels, wax paper, and toothpicks in the trash.


Return the pepper, dish soap,
dry

glass slides and beakers of water with pipettes to the supply
area.


Thorou
ghly
wash and dry

the beaker that contained pepper and soap so that neither residue
remains in the beaker and return the beaker to the supply area.


Wipe off and dry your desk tops.


Wash your hands and then return your goggles to the cabinet.