Mrs. McElveen Biology I

Water About percent of an organism is composed of water  About percent of an organism is composed of 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: What are the three states of water?What are the three states of water? Answer:Answer: 1.ice1.ice2.liquid 3.water vapor (gas)

The States of Water GAS SOLID LIQUID

Water Properties Polarity Cohesiveness Adhesiveness Surface Tension Capillary Action

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)

Cohesion Cohesion-Water molecules are attracted to other water molecules.Cohesion-Water molecules are attracted to other water molecules. Hydrogen bonds (H- bonds) cause these water molecules to stick togetherHydrogen bonds (H- bonds) cause these water molecules to stick together Rain falls in droplets, rather than a fine mist because water has strong cohesion which pulls its molecules tightly together, forming droplets..

Surface tension 1. Related to cohesion (H-bonds) (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.

Adhesion Adhesion- when water is attracted to other materials. The attractive force between unlike molecules This is the reason that water is a glass is not horizontal across, but rather has a downward curvature. The water molecules are attracted to the side of the glass, and cling to it.

Capillary Action Capillary action The movement of a liquid along the surface of a solid caused by the attraction of molecules of the liquid to the molecules of the solid.Capillary action is related to the adhesive properties of water. The movement of a liquid along the surface of a solid caused by the attraction of molecules of the liquid to the molecules of the solid. 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. Aides in the transport of water from roots to the leaves. Aides in the transport of water from roots to the leaves. teGohttps:// teGohttps:// teGohttps:// teGo

Water (H 2 O) & Solutions  Water is known as the universal solvent Water dissolves 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

Water (H 2 O) Remember: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).

Solutions & Suspensions Solute-substance being dissolved in the solutionSolute-substance being dissolved in the solution Solvent-substance in which solute is being dissolvedSolvent-substance in which solute is being dissolved Suspensions-mixtures of non-dissolved material and waterSuspensions-mixtures of non-dissolved material and water

ACIDS/BASES

Acids & Bases The degree of acidity or alkalinity (basic) is important in organismsThe 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 DissociationThe 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 H GOES TO----- H+ + OH- H GOES TO----- H+ + OH- OH- called hydroxide ion; H+ called hydrogen ionOH- called hydroxide ion; H+ called hydrogen ion

Acids & Bases Cont… Acidity or alkalinity is a measure of the relative amount of H+ and OH- ions dissolved in a solutionAcidity or alkalinity is 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- ionsNeutral solutions have an equal number of H+ and OH- ions Acids have more H 3 O+ ions than OH- ions; taste sour; and can be corrosiveAcids have more H 3 O+ ions than OH- ions; taste sour; and can be corrosive Bases contain more OH- ions than H 3 O+ ions; taste bitter; & feel slipperyBases contain more OH- ions than H 3 O+ ions; taste bitter; & feel slippery

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

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

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

Examples of Common Acids citric acid (from certain fruits and veggies, notably citrus fruits) ascorbic acid (vitamin C, as from certain fruits) vinegar (5% acetic acid) carbonic acid (for carbonation of soft drinks) lactic acid (in buttermilk) Examples of Common Bases detergents soap lye (NaOH) household ammonia

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

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

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

The lower the pH the stronger the acidThe lower the pH the stronger the acid The higher the pH the stronger the baseThe higher the pH the stronger the base pH 7.0 is neutralpH 7.0 is neutral

Strong/Weak Acids & Bases

Acids Proton donorProton donor High number of H + - protons and low # of OH -High number of H + - protons and low # of OH - Examples: HCl (hydrochloric acid)Examples: HCl (hydrochloric acid) H 2 SO 4 (sulfuric acid)-ACID RAIN H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+H+ OH -

Base Proton acceptorProton acceptor Low number of H + and high # of OH -Low number of H + and high # of OH - Examples:NaOH (sodium hydroxide)Examples:NaOH (sodium hydroxide) NH 3 (ammonia) OH - H+H+H+H+

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

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