1 / 23

Chapter 3: Water and Life

Chapter 3: Water and Life. WATER. Objectives. Importance of H bonds to properties of water 4 unique properties of water Interpreting a pH scale Importance of buffers in biological systems. Structure of Water. Structure key to special properties Structure dictates function Polarity

oren
Télécharger la présentation

Chapter 3: Water and Life

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 3: Water and Life

  2. WATER

  3. Objectives • Importance of H bonds to properties of water • 4 unique properties of water • Interpreting a pH scale • Importance of buffers in biological systems

  4. Structure of Water • Structure key to special properties • Structure dictates function • Polarity • Hydrogen bonding • Each molecule can form max 4

  5. Fig. 3-2 – Hydrogen bond + H —— O – —— + H + – – +

  6. 4 Properties of Water • Cohesion • Moderation of temperature • Ice floats on liquid water • Water as a solvent

  7. Properties of Water: Cohesive Behavior • Cohesion • Water linked to water • Responsible for surface tension • Partial charges make water “sticky” • Adhesion • Clinging of one substance to another • Transpiration • Water moves through xylem to open stomata • What roles do cohesion and adhesion play ? • How does polarity of water contribute to its cohesive and adhesive properties?

  8. Fig. 3-3 Adhesion Water-conducting cells Direction of water movement Cohesion 150 µm

  9. Concept Check • How does polarity of water contribute to its cohesive and adhesive properties? • How might Rainex alter the properties of glass to allow it to shed water. • Discuss with a partner then we will discuss as a class.

  10. Properties of Water: Ability to moderate Temperature • 2. Moderation of temperature • Specific heat: amount of heat required to change 1g of substance 1 degree C • Water has very high specific heat • Implications to earths climate • Oceans • Organisms • Heat of vaporization: amount of heat to convert 1g of liquid to gas • Water has high heat of vaporization

  11. Evaporative cooling • Evaporation is transformation of a substance from liquid to gas • As a liquid evaporates, its remaining surface cools, a process called evaporative cooling • Evaporative cooling helps stabilize temperatures in organisms and bodies of water

  12. Specific Heat • Water’s high specific heat can be traced to hydrogen bonding • Heat is absorbed when hydrogen bonds break • Heat is released when hydrogen bonds form • The high specific heat of water minimizes temperature fluctuations to within limits that permit life

  13. Properties of Water: Expansion Upon Freezing • 3. Ice insulates large bodies of water • Ice floats • Moderates temps by not allowing large bodies of water to freeze solid • What are affects on pond life? • 104.5 bond angle

  14. Fig. 3-6a Hydrogen bond Liquid water Hydrogen bonds break and re-form Ice Hydrogen bonds are stable

  15. Properties of Water: Versatility as a Solvent • 4. Water as a solvent • Solvent • Solute • Solution • Hydrophobic substances • Hydrophilic substances • Sphere of hydration

  16. Fig. 3-8bc (b) Lysozyme molecule (purple) in an aqueous environment (c) Ionic and polar regions on the protein’s surface attract water molecules.

  17. Deriving pH equation • In any aqueous solution at 25°C the product of H+ and OH– is constant and can be written as [H+][OH–] = 10–14 • The pH of a solution is defined by the negative logarithm of H+ concentration, written as pH = –log [H+] • For a neutral aqueous solution [H+] is 10–7 = –(–7) = 7

  18. Fig. 3-UN2 H H H O O O O H H H H H 2H2O Hydroxide ion (OH–) Hydronium ion (H3O+)

  19. Acids & Bases • Acids and bases alter [H+] • pH of pure water is 7 • How does HCl increase the acidity ? • Increase [H] • How does NaOH decrease acidity ? • Decrease [H] • direct bases NH3 gas • Indirect NaOH

  20. Fig. 3-9 pH Scale 0 1 Battery acid Gastric juice, lemon juice 2 H+ H+ H+ Vinegar, beer, wine, cola OH– 3 H+ H+ OH– Increasingly Acidic [H+] > [OH–] H+ H+ H+ 4 Tomato juice Acidic solution Black coffee 5 Rainwater 6 Urine OH– Saliva OH– Neutral [H+] = [OH–] 7 Pure water OH– H+ H+ OH– OH– Human blood, tears H+ H+ H+ 8 Seawater Neutral solution 9 10 Increasingly Basic [H+] < [OH–] Milk of magnesia OH– OH– 11 OH– H+ OH– Household ammonia OH– OH– OH– H+ 12 Basic solution Household bleach 13 Oven cleaner 14

  21. Importance of Buffers to Biological Systems • Carbonic acid and hyperventilation • Rapid breathing • Blood CO2 concentration decreases • Blood carbonic acid levels decrease • Blood pH changes from normal • Adverse physiological effects • Dizziness • Visual impairment • Fainting • Seizures • Death

  22. Acids and Bases • pH scale • pH = –log [H+] • 0-14 • Lower more acidic < 7 • Higher more basic > 7 • Acids: Excess H+ ions • Bases: Excess OH- • Pure water is neutral • Buffers: minimize changes in pH • Can accept or give H+ ions when needed • Carbonic Acid (H2CO3) moderates pH changes in blood plasma and in the ocean

  23. Summary and Review • List and explain the four properties of water that emerge as a result of its ability to form hydrogen bonds • Distinguish between the following sets of terms: hydrophobic and hydrophilic substances; a solute, a solvent, and a solution • Define acid, base, and pH • Explain how buffers work

More Related