1. Water – pg 5 Chapter 3

2. 1. Overview H 2 O Water is required by all living things – makes life possible Cells are surrounded by water Cells are 70-90% water Earth is ~75% water Exists in nature as a solid, liquid, and vapor

3. 1. Polar Polar – opposite ends of a molecule have opposite charge Oxygen is more electronegative than Hydrogen Oxygen – partial negative charge – electrons are pulled toward it Hydrogen – partial positive charge

4. 2. Hydrogen Bonding Partial (+) charge on the hydrogen on H 2 O is attracted to the partial (-) charge of the oxygen on another H 2 O and forms a weak hydrogen bond Each water molecule can form up to 4 H-bonds Hydrogen bonds + + H H + +  – –  – –  – –  – –

5. Draw a water molecule and label the atoms. Show the charges on each atom in the molecule. Draw 4 other water molecules bonding to the original water molecule in the correct locations. Circle the hydrogen bonds between each water molecule. Below your diagram summarize what you know about water and how it holds itself together. Diagram – pg 4

6. 3. Emergent properties of water that provide stability for life. – pg 7

7. 3. Emergent properties of water that provide stability for life. 1. Cohesion – many H 2 O molecules stick together via hydrogen bonding Allows for water and nutrient transport in plants from the roots to the leaves H 2 O “pulls” up when it evaporates through the leaves

8. 3. Emergent properties of water that provide stability for life. 2. Surface Tension – how difficult it is to break the surface of water Water has a higher surface tension than other liquids Invisible film Related to cohesion Many animals walk or run on water

9. 3. Emergent properties of water that provide stability for life. 3. Adhesion – the clinging of one substance to another Water sticks to the sides of cell walls in plants Water sticks to glass – meniscus Ex: allows water to travel “up” a tree without falling.

10. 3. Emergent properties of water that provide stability for life. 4. Capillary Action – cohesion and adhesion working together to move a liquid. Ex: paper towels absorbing water.

11. Water Chart - Pg 6 Life ExampleH 2 O PropertyExplanation 1.Sweating 2.Plants getting water from roots to leaves 3.Moderate temps on coastal regions 4.Salt (NaCl-) dissolving to allow proper functioning of the nervous system 5.Stable body temp in extreme temps 6.In Arctic habitats, ice creates an insulating layer atop water

12. 3. Emergent properties of water that provide stability for life. – pg 9 5. Water moderates temperature Specific Heat – amount of energy that must be absorbed or lost to change 1g by 1 o C Water has a high specific heat compared to other substances = 1calorie per 1gram per 1 o C Absorbs heat from the air when warmer and releases heat into the air when cooler Requires lots of energy to make a drastic change to the temp of water because the MANY hydrogen bonds must be broken Water minimizes temp. fluctuations Sweating and release of water from plants cools terrestrial organisms

13. 3. Emergent properties of water that provide stability for life. Vaporization – evaporation Transformation of a liquid to a gas Molecules move fast enough to “escape” liquid form Heating liquid = faster molecule movement Heat of vaporization = amount of heat a liquid must absorb for 1g to change from liquid to gas. Evaporative Cooling – As the water turns to gas and evaporates, the heat is taken with it and what is left behind is cooled

14. Temperature Moderation - Pg 8 Temperature Moderation - Pg 8 Bubble map for Temp. Moderation Summarize how water helps moderate the temperature of living things. Temp. Moderation

15. 4. Properties of water that provide stability for life. – pg 11 6. Density of H 2 O Ice is less dense than water – expands instead of contracts when below 4 O C Oceans and lakes don’t freeze because the ice floats and insulates the life below it

16. Ice Hydrogen bonds are stable Liquid water Hydrogen bonds break and re-form Hydrogen bond

17. 3. Emergent properties of water that provide stability for life.

18. 7. Water is the solvent of life – dissolves other substances to form aqueous solutions Effective at dissolving ionic and polar substances EX: salt water Water – solvent – does the dissolving NaCl – solute – gets dissolved Hydrophilic – water loving Ionic bonds or polar molecules Hydrophobic – water fearing Covalent bonds and non-polar molecules

19. Hydrophilic vs. Hydrophobic - Pg 10 Hydrophilic vs. Hydrophobic - Pg 10 Create a T-chart to compare the characteristics of hydrophilic and hydrophobic substances. Give at least one example of each. Summarize how hydrophilic an hydrophobic substances interact with water and WHY!! HydrophilicHydrophobic

20. 4. Dissociation  Acids + Bases – pg 13 A hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other: H 2 O  H + (H 3 O + ) + OH - Increase in H+ = acid Increase in OH- = base = decrease in H+ H H H H H H H H O O OO 2H 2 OHydronium ion (H 3 O + ) Hydroxide ion (OH – )

21. 5. pH 0-6.999 – acidic 7 - neutral 7.0001-14 – basic Living cells require an internal pH ~ 7 pH = - log [H+] [H+] = 10 –4  pH = 4

22. 6. Buffers Maintain the pH of a solution in the presence of an acid or base. Blood = pH 7.4 Bicarbonate buffer is found in blood plasma Organisms use buffers to maintain homeostasis Accept H+ when they are in excess. Donate H+ when they are depleted

23. pH - Pg 12 Complete the table. Summarize pH and explain how it relates to acids, bases, water and is regulated. [H + ][OH - ]pHAcidic, Basic, or Neutral 10 -11 3Acidic 10 -8 10 -7 1

24. Summary – pg 14-15 Write a minimum of a one page summary using at least 10 terms from the terms for summaries list. Highlight or underline each term as you use them in the correct context.