1. WATER AND THE FITNESS OF THE ENVIRONMENT

2. YOU MUST KNOW… THE IMPORTANCE OF HYDROGEN BONDING TO THE PROPERTIES OF WATER FOUR UNIQUE PROPERTIES OF WATER, AND HOW EACH CONTRIBUTES TO LIFE ON EARTH HOW TO INTERPRET THE pH SCALE THE IMPORTANCE OF BUFFERS IN BIOLOGICAL SYSTEMS

3. CONCEPT 3.1 THE POLARITY OF WATER MOLECULES RESULTS IN HYDROGEN BONDING

4. Water H 2 O As we know - water is polar The end bearing the oxygen atom has a slightly negative charge while the hydrogen atoms have a slightly positive charge Since oxygen is larger, it gives water a slight overall charge called polarity

5. POLAR BONDING Polarity really does allow bonding They are hydrogen bonds and they are very weak They last for fractions of a second Continuously break and reform Water has an uneven distribution of electrons between hydrogen and oxygen atoms creating polarity Polarity allows bonding The bonds are very weak hydrogen bonds They last for fractions of a second and continuously break and reform + + -

6. CONCEPT 3.2 FOUR EMERGENT PROPERTIES OF WATER CONTRIBUTE TO EARTHS FITNESS FOR LIFE

7. EMERGENT PROPERTIES COHESION ( WORKS WITH ADHESION AND TRANSPIRATION) SPECIFIC HEAT INSULATION OF BODIES OF WATER BY FLOATING ICE ACTS AS A SOLVENT -HYDROPHILIC - WATER SOLUBLE AND INCLUDE IONIC COMPOUNDS AND POLAR MOLECULES -HYDROPHOBIC – DONT DISSOLVE IN WATER AND ARE NONPOLAR SUCH AS OILS

8. COHESION The natural attraction of a water molecule to other water molecules is called cohesion

9. COHESION Cohesion: attraction between same molecules, causes molecules to draw inward at surface creates surface tension Can be seen as water droplets form

10. ADHESION The attraction of a water molecule to another polar molecule is adhesion Molecules such as soil and clay (dust) Surfaces like glass or paper straws Certain clothing fibers and … animal hair

11. ADHESION Adhesion: attraction between different molecules, causes water to bend at the surface and clinging of one substance to another

12. ADHESION Can be seen as water droplets form on the spider web (another polar surface)

13. TRANSPIRATION 1. We know that gravity is ALWAYS pulling on objects with mass 2. Yet water can move up a plant with relative ease - How can this happen? 3. The water molecules cling to each other by cohesion and water and minerals cling to the walls of the xylem tubes by adhesion 4. This property of adhesion is called capillary action

15. Review of Polarity Polarity hydrogen bonding cohesion adhesion surface tension capillary action Forces Properties

16. SPECIFIC HEAT The amount of heat required to raise or lower the temperature of a substance by 1 degree Celsius Water exhibits evaporative cooling: removes heat when it evaporates from a surface Ex: sweating cools skin

17. INSULATION Water expands during freezing: expands into crystal formation releasing heat Ex: rocks broken up by ice creating soil; ice layer protects fruit from freezing

18. SOLVENT Dissolves many other substances due to polarity Differences in charges pulls/pushes substances apart HYDROPHILIC SUBSTANCES – are water-soluble and may be polar HYDROPHOBIC SUBSTANCES – are nonpolar and do not dissolve in water EX. oils

19. CONCEPT 3.3 ACIDIC AND BASIC CONDITIONS AFFECT LIVING ORGANISMS

20. 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

21. ACIDS: release H + when mixed with water Sour, corrosive Ex: HCl, H 2 SO 4 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

22. 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