102 water p h notes 2010


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102 water p h notes 2010

  1. 1. Biology 102 A Properties of Water And Acids/BasesSB1.d. Explain the impact of water on life processes.
  2. 2. Why is water important tohumans?• 2/3 of the weight of a cell is WATER!• Look at all the important uses of water in the body…
  3. 3. What properties of water make it souseful 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. 4. What properties of water makeit so useful and important?2. Water is called “Universal solvent”:a. Differences in charges pulls/pushes substances apart
  5. 5. What properties of watermake it so useful andimportant? 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. 6. What properties of water makeit so useful and important?4. Water moves by capillary actiona.Capillary action- water molecules pull each other up against gravityb.This is how trees get water from their roots to their leaves.
  7. 7. What properties of water makeit so useful and important?5. Water exhibits evaporative cooling:a.removes heat when it evaporates from a surface- ex: sweatingb.Stores heat- helps maintain earth’s temperature
  8. 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 soilb. Also less dense when frozen so floats on liquid water- prevents entire ponds from freezing- which would kill animals in pond
  9. 9. So why is water so important toLIFE?• 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. 10. What is the pH scale? Measures the concentr ation of Hydroge n (H+) ions in a solution
  11. 11. What is an ACID?1. release H+ when mixed with water2. 0-6 on pH scale3. Sour, corrosive4. Always have H at front of formula5. Ex: HCl is hydrochloric acidWhat is a BASE?1. release hydroxide (OH-) when mixed with water2. 8-14 on pH scale3. Bitter, slippery, usually in cleaners4. Always have OH at end of Neutral: H+ ions and OH- ions are formula equal so it is neutral. They are 7 on pH5. Ex: NaOH is sodium hydroxide scale.
  12. 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. 13. What is a buffer?1. Body chemicals thatprevent sharp changesin pH so keep solutionneutral2. Help to control pHin blood, digestivetract, etc. to maintainhomeostasis
  14. 14. Quiz 21. Your saliva measures 7 on the pH scale, it is a(n) ___ solution? a. acidic b. basic c. neutral2. The ___ property of water helps in the formation of soil. a. capillary action b. expansion during freezing c. evaporative cooling3. Laundry detergent typically has a pH of 3 which indicates a(n) ___ solution? a. acidic b. basic c. neutral4. The use of ___ helps to maintain a certain pH in our bodies maintaining homeostasis. a. buffers b. bases c. acids5. The ___ property of water removes heat helping to cool your skin through sweating. a. capillary action b. evaporation c. cohesion