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Biology. Properties of Water And Acids/Bases (pH) SB1.d. Explain the impact of water on life processes. 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…. What properties of water make it so useful and important?.

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Biology

Properties of Water

And

Acids/Bases (pH)

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


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…


What properties of water make it so useful and important?

  • 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


What properties of water make it so useful and important?

2. Water is called “Universal solvent”:

a. Differences in charges pulls/pushes substances apart so they dissolve


What properties of water make it so useful and important?

3.Water is cohesive & adhesive which creates surface tension

Cohesive- water molecules stick to each other

Adhesive- water molecules stick to other surfaces

Surface tension- like a skin of water

Ex: how some insects walk on water

Surface tension created by cohesiveness of water


What properties of water make it so useful and important?

4. Water moves by capillary action

  • Capillary action- water molecules pull each other up against gravity

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


What properties of water make it so useful and important?

5. Water exhibits evaporative cooling:

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

  • Stores heat- helps maintain earth’s temperature


What properties of water make it so useful and important?

6. Water expands during freezing:

  • ex: rocks broken up by ice to create soil

  • Also less dense when frozen so floats on liquid water- prevents entire ponds from freezing- which 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?

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 do with Biology?

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

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


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


  • Your stomach juices measure 2 on the pH scale, it is a(n) ___ solution.

  • a. acidic b. basic c. neutral

  • The ___ property of water helps in the formation of soil.

  • a. capillary action b. expansion during freezing c. evaporative cooling

  • Water has a slight charge on each end. This property makes water a great solvent. This property is called

    • Polarityb. Capillary actionc. Frost wedging

  • 4. Insects can walk on H2O & paper clips are able to float on H2O because of water’s

    • Surface tension from hydrogen bonds

    • Cohesion with other molecules

    • Adhesion with its own water molecules

    • High specific heat

  • 5. Trees are able to move water from the roots to the leaves by the property of water known as

    • Polarityb. Capillary actionc. Surface tension

  • 6. The ___ property of water removes heat helping to cool your skin through sweating.

  • a. capillary action b. evaporation c. cohesion


Match these pictures with their water properties:

1.

6.

  • Cohesion & adhesion

  • Capillary action

  • Evaporative cooling

  • Surface tension

  • Expansion during freezing

  • Polarity- universal solvent

2.

4.

5.

3.


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