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Biology I

Water Properties & pH. Biology I.  About 60-90 percent of an organism is composed of water. Water.  Water is used in most reactions in the body.  Water is called the universal solvent.  Water is the single most abundant compound in living thing. Question:.

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Biology I

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  1. Water Properties & pH Biology I

  2. About 60-90 percent of an organism is composed of water Water Water is used in most reactions in the body Water is called the universal solvent Water is the single most abundant compound in living thing

  3. Question: • What are the three states of water? • Answer: • 1.ice 2.liquid 3.water vapor (gas)

  4. The States of Water GAS LIQUID SOLID

  5. Water Properties Polarity Cohesiveness Adhesiveness Surface Tension

  6. Polarity of Water • Water is a “polar” molecule, meaning that there is an uneven distribution of electrons. • Water has a partial negative charge near the oxygen atom due to the unshared pairs of electrons, and partial positive charges near the hydrogen atoms. • This causes them to stick like small magnets, making a hydrogen bond (weakest bonds, easy to break & easily formed again)

  7. Water (H2O) Cohesion & Adhesion 1. Hydrogen bonds (H-bonds) cause water molecules to stick together. 2. Aides in the transport of water from rootsto the leaves. 3. Water is attracted to other water, this is called cohesion. 4. Water can also be attracted to other materials. This is called adhesion. The oxygen end of water has a negative charge and the hydrogen end has a positive charge. The hydrogen of one water molecule are attracted to the oxygen from other water molecules. This attractive force is what gives water its cohesive and adhesive properties.

  8. Surface tension Surface tension 1. Related to cohesion (H-bonds) 2. Allow water striders (insects) to walk on water. Surface tension is the name we give to the cohesion of water molecules at the surface of a body of water.

  9. Capillary Action • Surface tension is related to the cohesive properties of water. Capillary action however, is related to the adhesive properties of water. You can see capillary action 'in action' by placing a straw into a glass of water. The water 'climbs' up the straw. What is happening is that the water molecules are attracted to the straw molecules. When one water molecule moves closer to a the straw molecules the other water molecules (which are cohesively attracted to that water molecule) also move up into the straw.

  10. Water (H2O) & Solutions Water is known as the universal solvent Waterdissolves an enormous variety of solutes. solvent (water) + solute (salt) solution Not all things are pure substances. Some are mixtures that contain more than one substance. Solutions are mixtures in which one or more substances are evenly distributed in another substance

  11. Water (H2O) • Remember: 1. Water is a good solvent and is hydrophilic(water loving) for other polar molecules and ions. 2. Hydrophobic (water hating) interactions occur between water and non-polar molecules like fat (lipids).

  12. Solutions & Suspensions • Solute-substance being dissolved in the solution • Solvent-substance in which solute is being dissolved • Aqueous solution-solution in which water is the solvent • Suspensions-mixtures of non-dissolved material and water

  13. Acids & Bases • The degree of acidity or alkalinity (basic) is important in organisms • The force of attraction between molecules is so strong that the oxygen atom of one molecule can actually remove the hydrogen from other water molecules; called Dissociation •  H20-----GOES TO----- H+  +  OH- • OH- called hydroxide ion; H+ called hydrogen ion

  14. Acids & Bases Cont… • Acidity or alkalinityis a measure of the relative amount of H+ and OH- ions dissolved in a solution • Neutral solutions have an equal number of H+ and OH- ions • Acids have more H3O+ ions than OH- ions; taste sour; and can be corrosive • Bases contain more OH- ions than H3O+ ions; taste bitter; & feel slippery  

  15. Acids and Bases • One of the most important aspects of a living system is the degree of acidity or alkalinity

  16. Acids • Number of hydronium ions in solutions is greater than the number of hydroxide ions • HCl  H+ + Cl-

  17. Bases • Number of hydroxide ions in solution is greater than the number of hydronium ions • NaOH  Na+ + OH-

  18. pH Scale • Compares the relative concentration of H3O+ ions and OH- ions • Scale ranges from 0 to 14; 0-3 is very acidic; 7 is neutral; 11-14 is very basic or alkaline • Litmus paper, phenolphthalein, pH paper, & other indicators that change color can be used to measure pH

  19. pH Cont….. • Using litmus paper: An acid turns blue litmus paper red and a base turns red litmus paper blue.

  20. pH Scale • Scale for comparing the relative concentrations of hydronium ions and hydroxide ions in a solution • Scale ranges from 0 to 14

  21. The lower the pH the stronger the acid • The higher the pH the stronger the base • pH 7.0 is neutral

  22. H+H+H+H+H+ H+H+H+H+H+ H+H+H+H+H+ OH- OH- Acids • Proton donor • High number of H+ - protons and low # of OH- • Examples: HCl (hydrochloric acid) H2SO4 (sulfuric acid)- ACID RAIN

  23. OH- OH- OH- OH- OH- OH- OH- OH- OH- OH- OH- OH- H+H+ Base • Proton acceptor • Low number of H+ and high # of OH- • Examples: NaOH (sodium hydroxide) NH3 (ammonia)

  24. H+ H+ H+ OH- OH- OH- OH- OH- OH- H+H+ H+ Neutral Solution • pHof 7 is neither acidic or basic. • It is said to be neutral. • This means that there are as manyH+ as OH-. • Pure water and blood are neutral.

  25. Buffers • Control of pH is important to organisms • Enzymes function only within a narrow pH range; usually neutral • Buffers neutral acids or bases in organisms to help control pH

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