Biology 102 ABiology 102 A

Properties of WaterProperties of Water

And And

Acids/BasesAcids/Bases

SB1.d. Explain the impact of SB1.d. Explain the impact of water on life processes.water on life processes.

Why is water important to Why is water important to humans?humans?

• 2/3 of the weight 2/3 of the weight of a cell is of a cell is WATER!WATER!

• Look at all the Look at all the important uses important uses of water in the of water in the body…body…

What properties of water make What properties of water make it so useful and important?it so useful and important?

1.1.Water is polar:Water is polar:

a. Has a slight charge a. Has a slight charge on each end.on each end.

b. One side of water b. One side of water is “+” and the other is “+” and the other side is “-”side is “-”

c. This polarity c. This polarity enables water to enables water to dissolve many dissolve many substancessubstances

What properties of water What properties of water make it so useful and make it so useful and important?important?2. 2. Water is called Water is called

“Universal solvent”: “Universal solvent”:

a. Differences in a. Differences in charges pulls/pushes charges pulls/pushes substances apartsubstances apart

What properties of water What properties of water make it so useful and make it so useful and important?important?

3. Water is cohesive & adhesive which creates surface tensiona.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

What properties of water What properties of water make it so useful and make it so useful and important?important?4. 4. Water moves by Water moves by

capillary actioncapillary action

a.a.Capillary action- Capillary action- water molecules pull water molecules pull each other up each other up against gravityagainst gravity

b.b.This is how trees This is how trees get water from their get water from their roots to their leaves.roots to their leaves.

What properties of water What properties of water make it so useful and make it so useful and important?important?5. 5. Water exhibits Water exhibits

evaporative cooling: evaporative cooling:

a.a.removes heat when it removes heat when it evaporates from a evaporates from a surface- ex: sweatingsurface- ex: sweating

b.b.Stores heat- helps Stores heat- helps maintain earth’s maintain earth’s temperaturetemperature

What properties of water What properties of water make it so useful and make it so useful and important?important?

6. 6. Water expands during Water expands during freezingfreezing::

a.a.ex: rocks broken up by ice ex: rocks broken up by ice to create soilto create soil

b.b. Also less dense when frozen so Also less dense when frozen so floats on liquid water- prevents floats on liquid water- prevents entire ponds from freezing- entire ponds from freezing- which would kill animals in pondwhich would kill animals in pond

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

What is the pH scale?What is the pH scale?

Measures the concentration of Hydrogen (H+) ions in a solution

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 formula

5. Ex: NaOH is sodium hydroxide

Neutral: H+ ions and OH- ions are equal so it is neutral. They are 7 on pH scale.

What’s the pH scale got to What’s the pH scale got to do with Biology?do with Biology?

• Chemical reactions in Chemical reactions in cells release and cells release and absorb hydrogen- absorb hydrogen- this can change pH.this can change pH.

• If pH levels in body If pH levels in body are not maintained, are not maintained, electrical chemistry electrical chemistry in body doesn’t work- in body doesn’t work- can lead to sickness.can lead to sickness.

Body Part/System Normal pH range

Blood pH 7.5 (neutral)

Urine/Saliva pH 6.5 (slightly acidic)

Stomach pH 1.5 (very acidic)

Intestine pH 8.5 (slightly alkaline)

What is a buffer?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

Quiz 2Quiz 21. 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