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Warm Up: Agree/ Disagree

Warm Up: Agree/ Disagree. T/F: All living things are 70-90% water T/F: Ice water is more dense than liquid water, which is why ice floats. T/F: Water can go against gravity. T/F: Water can become an acid.

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Warm Up: Agree/ Disagree

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  1. Warm Up: Agree/ Disagree • T/F: All living things are 70-90% water • T/F: Ice water is more dense than liquid water, which is why ice floats. • T/F: Water can go against gravity. • T/F: Water can become an acid. • T/F: Water contracts (shrinks) when it freezes which is why cans of soda burst in the freezer. 1

  2. QW: Agree/ Disagree • T/F: All living things are 70-90% water • T/F: Ice water is more dense than liquid water, which is why ice floats (less) • T/F: Water can go against gravity (trees) • T/F: Water can become an acid (acid rain) • T/F: Water contracts (shrinks) when it freezes which is why cans of soda burst in the freezer. (expands) 2

  3. Chapter 2: The Chemistry of Life • 2-2: Properties of Water • BIOLOGY 3

  4. Vocabulary • Cohesion • Adhesion • Mixture • Solution • Solute • Solvent • Suspension • pH Scale • Acid • Base • Buffer 4

  5. “The Blue Planet” 5

  6. The Water Molecule • Polarity: unequal sharing of electrons by H and O atoms • O atom has more electrons than H atom • Water molecule has bent shape with O atom at one end and H atoms at other end 6

  7. Hydrogen Bonds • The partial negative and positive charges (polarity) of water molecules make them attracted to each other • H bonds are not as strong as covalent or ionic bonds • Water can form multiple H bonds 7

  8. HYDROGEN BONDING • Cohesion: water molecules are attracted to each other by H bonds • Ex: water strider glides on top of water 8

  9. Adhesion • Adhesion: water molecules attracting to another substance (like glass) by H bonds • Ex:H2O sticks to side plant vessels • Ex: meniscus in graduated cylinder 9

  10. Mixtures • Mixture: material made of 2 or more elements or compounds mixed together • Solution: mixture in which one or more substance mixed in another • Solute: substance that is dissolved (Na+Cl-) • Solvent: substance in which the solute dissolves Salt dissolving in water 10

  11. Suspensions • Suspensions: mixtures of water and nondissolved particles • Ex: blood 11

  12. Formation of Acids & Bases • A water molecule can react to form ions as in this reaction: • The number of positive ions is equal to negative, so water is neutral H2O H+ + OH- water hydrogen ion + hydroxide ion Banff 12

  13. The pH Scale • pH scale: system to measure concentration of H+ ions in a solution • Ranges from 0 to 14 • pH 7 = neutral • Ex: water • Each step on pH scale represents a factor of 10 • Ex: pH 4 has 10 x as many H+ ions as pH 5 13

  14. Acids • Acid: any compound that forms H+ ions in a solution • Contains a higher concentration of H+ ions than pure water • pH values below 7 • Ex: hydrochloric acid produced by the stomach • Ex: lemons 14

  15. Bases • Base: compound that produces hydroxide ions (OH-) in solution • Contain lower concentrations of H+ ions than pure water • pH values above 7 • Ex: bleach 15

  16. Buffer • Buffers: weak acids or bases that can react with strong acids or bases to prevent sudden changes in pH • Helps maintain homeostasis in our bodies • Ex: carbonic acid in our blood • Ex: TUMS for stomach acid 16

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