Mrs. McElveenMrs. McElveen

Biology IBiology I

Water About 60-90 percent of an About 60-90 percent of an organism is composed of waterorganism 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:Question:• What are the three What are the three

states of states of waterwater??

• Answer:Answer:• 1.ice1.ice

2.liquid2.liquid

3.water vapor (gas)3.water vapor (gas)

The States of WaterGASGAS

SOLIDSOLID

LIQUIDLIQUID

Water PropertiesPolarityPolarity

Cohesiveness

Adhesiveness

Surface Tension

Capillary Action

Polarity of WaterPolarity of Water

Water is a Water is a ““polarpolar”” molecule, meaning that there is molecule, meaning that there is an uneven distribution of electrons.an uneven distribution of electrons.

Water has a partial negative charge near the Water has a partial negative charge near the oxygen atom due to the unshared pairs of oxygen atom due to the unshared pairs of electrons, and partial positive charges near the electrons, and partial positive charges near the hydrogen atomshydrogen atoms..

This causes them to stick like small magnets, This causes them to stick like small magnets, making a hydrogen bond (making a hydrogen bond (weakest bonds, easy to weakest bonds, easy to break & easily formed againbreak & easily formed again))

Cohesion

• Cohesion-Water Cohesion-Water molecules are attracted molecules are attracted to other water to other water molecules. molecules.

• Hydrogen bonds (H-Hydrogen bonds (H-bonds) cause these bonds) cause these water molecules to water molecules to stick togetherstick together

• Rain falls in droplets, Rain falls in droplets, rather than a fine mist rather than a fine mist because water has strong because water has strong cohesion which pulls its cohesion which pulls its molecules tightly together, molecules tightly together, forming droplets..forming droplets..

Surface tensionSurface tensionSurface tensionSurface tension

1. 1. Related to Related to cohesioncohesion

(H-bonds)(H-bonds)

2. 2. Allow water striders Allow water striders (insects) to walk on (insects) to walk on water.water.

Surface tensionSurface tension is the is the name we give to the name we give to the

cohesion of water cohesion of water molecules at the surface molecules at the surface

of a body of waterof a body of water. .

Adhesion

• Adhesion- when Adhesion- when water is attracted to water is attracted to other materials. The other materials. The attractive force attractive force between unlike between unlike moleculesmolecules

• This is the reason that water This is the reason that water is a glass is not horizontal is a glass is not horizontal across, but rather has a across, but rather has a downward curvature. The downward curvature. The water molecules are water molecules are attracted to the side of the attracted to the side of the glass, and cling to it. glass, and cling to it.

Capillary Action

• Capillary actionCapillary action is related to the adhesive properties of water. The movement of a The movement of a

liquid along the surface of a solid liquid along the surface of a solid caused by the attraction of molecules of caused by the attraction of molecules of the liquid to the molecules of the solid.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 Aides in the transport of water from rootsroots to to

the the leavesleaves..• https://www.youtube.com/watch?v=

VHnFMPxteGo

Water (HWater (H22O) & O) & SolutionsSolutions

Water is known as the universal solventWater is known as the universal solvent

WaterWater dissolves an enormous variety of dissolves an enormous variety of solutessolutes..

solvent (water)solvent (water) + + solute (salt)solute (salt) solutionsolutionNot all things are pure substances. Some Not all things are pure substances. Some

are mixtures that contain more than one are mixtures that contain more than one substance.substance.

SolutionsSolutions are mixtures in which one or are mixtures in which one or more substances are evenly distributed in more substances are evenly distributed in

another substanceanother substance

Water (HWater (H22O)O)• Remember:Remember:

1.1. WaterWater is a is a good solventgood solvent and is and is hydrophilichydrophilic (water loving)(water loving) for other for other polarpolar molecules and molecules and ionsions..

2.2. Hydrophobic (water hating)Hydrophobic (water hating) interactions interactions occur between occur between waterwater and and non-polarnon-polar molecules like molecules like fat (lipids).fat (lipids).

Solutions & Suspensions• SoluteSolute-substance being dissolved in the solution-substance being dissolved in the solution• SolvenSolventt-substance in which solute is being dissolved-substance in which solute is being dissolved

• SuspensionsSuspensions-mixtures of non-dissolved material and -mixtures of non-dissolved material and waterwater

ACIDS/BASES

Acids & Bases

• The degree of The degree of acidityacidity or or alkalinity (basic)alkalinity (basic) is is important in organismsimportant in organisms

• The force of attraction between molecules is so strong The force of attraction between molecules is so strong that the oxygen atom of one molecule can actually that the oxygen atom of one molecule can actually remove the hydrogen from other water molecules; remove the hydrogen from other water molecules; called called Dissociation Dissociation

•   HH220-----GOES TO----- H+  +  OH- 0-----GOES TO----- H+  +  OH-

• OH- OH- calledcalled hydroxide ion; H+  hydroxide ion; H+ calledcalled hydrogen ion hydrogen ion

Acids & Bases Cont…• Acidity or alkalinityAcidity or alkalinity is a measure of the is a measure of the

relative amount of relative amount of H+ and OH- ionsH+ and OH- ions dissolved in a solutiondissolved in a solution

• Neutral solutions Neutral solutions have an equal number of have an equal number of H+ and OH- ions H+ and OH- ions

• AcidsAcids have more have more HH33O+ ions O+ ions than than OH- ions;OH- ions; taste taste sour;sour; and can be corrosive and can be corrosive

• Bases Bases contain more contain more OH- ions OH- ions than than HH33O+ O+ ions; taste bitter; & feel slippery  ions; taste bitter; & feel slippery  

Acids and Bases

• One of the most important aspects of a living One of the most important aspects of a living system is the degree of acidity or alkalinitysystem is the degree of acidity or alkalinity

Acids

• Number of hydronium ions in solutions is Number of hydronium ions in solutions is greater than the number of hydroxide ionsgreater than the number of hydroxide ions

• HCl HCl H H++ + Cl + Cl--

Bases

• Number of hydroxide ions in solution is Number of hydroxide ions in solution is greater than the number of hydronium ionsgreater than the number of hydronium ions

• NaOH NaOH Na Na++ + OH + 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 Compares the relative

concentration of concentration of HH33O+ O+ ions ions and and OH- ionsOH- ions

• Scale ranges fromScale ranges from 0 to 14; 0 to 14; 0-3 0-3 is very is very acidic; 7 is acidic; 7 is neutral; 11-14 neutral; 11-14 is very is very basic or alkalinebasic or alkaline

• Litmus paper, Litmus paper, phenolphthalein, pH paper, phenolphthalein, pH paper, & other indicators that & other indicators that change color can be used to change color can be used to measure pH measure pH

pH Cont…..

• Using litmus paper: Using litmus paper: An acid turns blue An acid turns blue litmus paper red and a litmus paper red and a base turns red litmus base turns red litmus paper blue.paper blue.

pH Scale• Scale for Scale for

comparing the comparing the relative relative concentrations concentrations of hydronium of hydronium ions and ions and hydroxide ions hydroxide ions in a solutionin a solution

• Scale ranges Scale ranges from 0 to 14from 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

AcidsAcids

• Proton donorProton donor• High number of HHigh number of H+ + - - protons and low # of OHprotons and low # of OH--

• Examples:Examples: HCl (hydrochloric acid)HCl (hydrochloric acid)

HH22SOSO44 (sulfuric acid)- (sulfuric acid)- ACID ACID

RAINRAIN

H+H+H+H+H+

H+H+H+H+H+

H+H+H+H+H+

OH- OH-

BaseBase

• Proton acceptorProton acceptor• Low number of Low number of HH++ and high # of OH and high # of OH--

• Examples:Examples: NaOH (sodium hydroxide)NaOH (sodium hydroxide)

NHNH33 (ammonia) (ammonia)

OH-OH- OH-

OH-

OH-OH-OH-

H+H+

OH-OH-

OH-OH-OH-

Neutral SolutionNeutral Solution

• pHpH of 7 is neither of 7 is neither acidicacidic or or basic.basic.• It is said to be It is said to be neutral.neutral.• This means that there are as manyThis means that there are as many HH++ as as OHOH--..• Pure waterPure water and and bloodblood are are neutralneutral..

OH-

OH-

OH-OH-

H+H+ H+

OH-OH-

H+ H+ H+

Buffers

• Control of pH is Control of pH is important to important to organisms organisms

• EnzymesEnzymes function function only within a narrow only within a narrow pH range; pH range; usually usually neutralneutral

• Buffers Buffers neutral acids neutral acids or bases in organisms or bases in organisms to help control pH to help control pH