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LIFE DEPENDS ON THE UNIQUE PROPERITIES OF WATER

LIFE DEPENDS ON THE UNIQUE PROPERITIES OF WATER. Questions to think about . Why do put salt on the roads? Why do we salt a pot of pasta water? At a higher altitude why must we cook “boil” something longer? . Human Composition . Cells are 70% to 95% water . Plant Composition .

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LIFE DEPENDS ON THE UNIQUE PROPERITIES OF WATER

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  1. LIFE DEPENDS ON THE UNIQUE PROPERITIES OF WATER

  2. Questions to think about • Why do put salt on the roads? • Why do we salt a pot of pasta water? • At a higher altitude why must we cook “boil” something longer?

  3. Human Composition • Cells are 70% to 95% water

  4. Plant Composition • As much as 95% plants can be made of water

  5. Formula and Bonds Formula: H2O Bonds: Covalent- electrons are shared between Oxygen and Hydrogen

  6. How do we get Hydrogen Bonds? O H H Because Oxygen has 8 Protons (+) it pulls the electrons more (Electron HOG)Oxygen acts Negative- Hydrogen acts Positive

  7. Hydrogen Bonds • Hydrogen Bonds- weak bondsslightly positive H is attracted to the slightly negative O of another water molecule

  8. Polarity • Polar molecule: molecule in which opposite ends have opposite electric charges • Why? Water is a polar molecule: because Oxygen is an electron HOG • POLAR COVALENT BOND

  9. The polar nature of water and the effects of hydrogen bonding explain most of water's unique properties. • Cohesion • Adhesion • Solubility • Temperature moderation • The lower density of ice

  10. 1-inchpaperclip over-filled water 3oz Dixie cup Cohesion • Water “sticks” to each other because of hydrogen bonds • Surface tension

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  12. Adhesion • Water molecules are also attracted to certain other molecules. • Ex. In trees/plants water goes against gravity Called capillary action

  13. Water is the a Universal Solvent Water is able to dissolve other Polar &ionic compounds when mixed by causing the ions to break away and surround them. • Water dissolves Salt (Na+Cl-)

  14. Water (Polar) will not dissolve (Nonpolar) • Like dissolve Like • Water won’t dissolve oils

  15. Temperature and Water Boiling Point: 100 oC 212 oF • When you heat molecules move faster • When you cool molecules move slower • Water takes more energy to heat because energy must break hydrogen bonds

  16. Does water boil faster if you add salt to it? • Water Boils when it has enough energy for the molecules to leave

  17. Freezing Point 0 oC or 32 oF • What would happen if our oceans did not have salt in them? • Why do we put salt on our roads? • Why at effect does salt have on FREEZING POINT?

  18. LOW DENSITY OF ICE • Density- amount of matter in a volume • In most substances the solid state is more dense than the liquid state • Water is the opposite ICE IS LESS DENSE THAN WATER and will FLOAT

  19. LOW DENSITY OF ICE • WHY????? • Hydrogen bonds in ice (solid) keep molecules spaced out

  20. LOW DENSITY OF ICE • Floats • Ice insulates the liquid water below allowing life to persist

  21. Homework Questions Explain how the structure of water molecules results in attractions among them. Give an example of how cohesion among water molecules is important to living things.
 4. Name three conditions on Earth that make the planet suitable for life. 5. Explain one way in which water can moderate temperature.

  22. Does water boil faster if you add salt to it? • Water Boils when it has enough energy for the molecules to leave

  23. Why do we need salt in our ice, when making ice cream? Watch Video • Salt Decreases the freezing point What would happen if our oceans did not have salt in them?

  24. Why is this important for life? Water Boiling Point Ethanol Boiling Point

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