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Biology 102 A

Biology 102 A

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Biology 102 A

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  1. Biology 102 A Properties of Water And Acids/Bases

  2. Describe the properties of water that make it important to living things. • Water is polar: it has an uneven distribution of electrons between the hydrogen and oxygen atoms • One side of water is positive and the other is negative

  3. Water properties: • Water is cohesive • Cohesion: attraction between same molecules, causes molecules to draw inward at surface • Ex: allows some insects & spiders can “walk” on the surface • Water is adhesive • Adhesion: attraction between different molecules, causes water to bend at the surface • Ex: capillary action-pulls column of water up to the top of a plant

  4. Water is called “Universal solvent”: dissolves many other substances due to polarity • Differences in charges pulls/pushes substances apart • Water exhibits evaporative cooling: removes heat when it evaporates from a surface • Ex: sweating cools skin • Water expands during freezing: expands into crystal formation releasing heat • Ex: rocks broken up by ice creating soil; ice layer protects fruit from freezing Water properties:

  5. Acids, Bases and the pH scale • The pH scale measures the concentration of H+ ions (how acidic something is) • Ranges from 0-14 • At 7: H+ ions and OH- ions are equal so it is neutral • 0-7: acidic, has more H+ ions • 7-14: basic, has more OH- ions

  6. ACIDS: release H+ when mixed with water • Sour, corrosive • Ex: HCl, H2SO4 • Always have H at front of formula • BASES: release OH- when mixed with water • Bitter, slippery, usually in cleaners • NaOH, CaOH • Always have OH at end of formula

  7. What is a buffer? • Buffers are weak acids or bases that react with strong acids and bases to prevent sharp changes in pH • Helps to neutralize • Help to control pH in blood, digestive tract, etc. to maintain homeostasis

  8. Quiz 3 • Your saliva measures 7 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 • Laundry detergent typically has a pH of 3 which indicates a(n) ___ solution? • a. acidic b. basic c. neutral • The use of ___ helps to maintain a certain pH in our bodies maintaining homeostasis. • a. buffers b. bases c. acids • The ___ property of water removes heat helping to cool your skin through sweating. • a. capillary action b. evaporation c. cohesion

  9. Create and Design • Your assignment is to create and design a colorful and visually pleasing pH scale. Using pg 165 in your book to help you, create a scale of reference to show what some common substances pH numbers are. Use different colors and sketch pictures of the common items. • Pick up a piece of paper and get started.