Here are the answers to the quiz: 1. c 2. b 3. a 4. a 5. b

1. Biology 102 A
Properties of Water
And
Acids/Bases
SB1.d. Explain the impact of
water on life processes.

2. Why is water important to
humans?
• 2/3 of the weight of
a cell is WATER!
• Look at all the
important uses of
water in the body…

3. What properties of water make it so
useful and important?
1. Water is polar:
a. Has a slight
charge on each end.
b. One side of water
is “+” and the other
side is “-”
c. This polarity
enables water to
dissolve many
substances

4. What properties of water make
it so useful and important?
2. Water is called
“Universal solvent”:
a. Differences in
charges pulls/pushes
substances apart

5. What properties of water
make it so useful and
important?
3. Water is cohesive &
adhesive which creates
surface tension
a.Cohesive- water molecules stick to each
other
b.Adhesive- water molecules stick to other
surfaces
c.Surface tension- like a skin of water
d.Ex: how some insects walk on water
Surface tension created by cohesiveness
of water

6. What properties of water make
it so useful and important?
4. Water moves by
capillary action
a.Capillary action-
water molecules pull
each other up against
gravity
b.This is how trees get
water from their roots
to their leaves.

7. What properties of water make
it so useful and important?
5. Water exhibits
evaporative cooling:
a.removes heat when it
evaporates from a
surface- ex:
sweating
b.Stores heat- helps
maintain earth’s
temperature

8. What properties of water make
it so useful and important?
6. Water expands during
freezing:
a.ex: rocks broken up by ice
to create soil
b. Also less dense when frozen so
floats on liquid water- prevents
entire ponds from freezing-
which would kill animals in pond

9. So why is water so important to
LIFE?
• Used in chemical reactions in cells
• Helps create soil
• Plants use to make food for all
• Used to dissolve materials needed in cells
• Helps maintain Earth’s temperature

10. What is the pH scale?
Measures the
concentr
ation of
Hydroge
n (H+)
ions in a
solution

11. What is an ACID?
1. release H+ when mixed with
water
2. 0-6 on pH scale
3. Sour, corrosive
4. Always have H at front of formula
5. Ex: HCl is hydrochloric acid
What is a BASE?
1. release hydroxide (OH-) when
mixed with water
2. 8-14 on pH scale
3. Bitter, slippery, usually in
cleaners
4. Always have OH at end of
Neutral: H+ ions and OH- ions are
formula
equal so it is neutral. They are 7 on pH
5. Ex: NaOH is sodium hydroxide scale.

12. What’s the pH scale got to do
with Biology?
• Chemical reactions in Body Part/System Normal pH range
cells release and Blood pH 7.5 (neutral)
Urine/Saliva pH 6.5 (slightly acidic)
absorb hydrogen- this
Stomach pH 1.5 (very acidic)
can change pH. Intestine pH 8.5 (slightly
alkaline)
• If pH levels in body
are not maintained,
electrical chemistry in
body doesn’t work-
can lead to sickness.

13. What is a buffer?
1. Body chemicals that
prevent sharp changes
in pH so keep solution
neutral
2. Help to control pH
in blood, digestive
tract, etc. to maintain
homeostasis

14. Quiz 2
1. Your saliva measures 7 on the pH scale, it is a(n) ___ solution?
a. acidic b. basic c. neutral
2. The ___ property of water helps in the formation of soil.
a. capillary action b. expansion during freezing c. evaporative cooling
3. Laundry detergent typically has a pH of 3 which indicates a(n) ___
solution?
a. acidic b. basic c. neutral
4. The use of ___ helps to maintain a certain pH in our bodies maintaining
homeostasis.
a. buffers b. bases c. acids
5. The ___ property of water removes heat helping to cool your skin through
sweating.
a. capillary action b. evaporation c. cohesion