Water and the Water and the

Fitness of the Fitness of the EnvironmentEnvironment

IntroductionIntroduction

Water makes life possible. All Water makes life possible. All organisms are made mostly of organisms are made mostly of water and live in an environment water and live in an environment dominated by water.dominated by water.

70-95% of all cells are water.70-95% of all cells are water.

¾ of the Earth is water.¾ of the Earth is water.

Water is found in 3 forms on Earth: Water is found in 3 forms on Earth: water, ice, water vapor.water, ice, water vapor.

Polar MoleculePolar Molecule

Water is a polar Water is a polar molecule- it is molecule- it is both slightly both slightly positive on positive on one end and one end and slightly slightly negative on negative on the other end.the other end.

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Hydrogen BondingHydrogen Bonding

Positive charge of Positive charge of one water one water molecule molecule attaches to attaches to negative charge negative charge of another of another water molecule.water molecule.

All properties of All properties of water are a water are a result of result of hydrogen hydrogen bonding.bonding.

Important Properties of Important Properties of WaterWater

•CohesionCohesion

•AdhesionAdhesion

•Surface TensionSurface Tension

•High Specific HeatHigh Specific Heat

•High Heat of VaporizationHigh Heat of Vaporization

•Ice FloatsIce Floats

•Universal SolventUniversal Solvent

Adhesion & Adhesion & CohesionCohesion

CohesionCohesion- water - water molecules molecules sticking to sticking to each other.each other.

AdhesionAdhesion- water - water molecules molecules sticking to sticking to other other substances.substances.

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Surface TensionSurface Tension

Due to cohesion, it Due to cohesion, it is difficult to is difficult to break the break the surface of water.surface of water.

Ex. Skipping a Ex. Skipping a rockrock

High Specific HeatHigh Specific HeatHigh Heat of VaporizationHigh Heat of Vaporization

• It is difficult to heat or cool water.It is difficult to heat or cool water.This helps stabilizes temperatures This helps stabilizes temperatures around the Earth.around the Earth.

• A lot of heat is absorbed to A lot of heat is absorbed to evaporate water.evaporate water.

Evaporation of sweat significantly Evaporation of sweat significantly cools the body surface.cools the body surface.

Ice FloatsIce FloatsIce is less dense than waterIce is less dense than water

Water is the Universal Water is the Universal SolventSolvent

Solute- substance Solute- substance that is dissolved.that is dissolved.

Solvent- substance Solvent- substance doing the dissolving.doing the dissolving.

Solution- Solution- homogenous homogenous mixture of 2 or mixture of 2 or more substances.more substances.

Biological fluids are Biological fluids are important solutions!important solutions!

Hydrophilic vs. Hydrophilic vs. HydrophobicHydrophobic

• Hydrophilic- polar or ionic substances Hydrophilic- polar or ionic substances that have an affinity for water.that have an affinity for water.

salts, sugars, ions, etc.salts, sugars, ions, etc.

• Hydrophobic- nonpolar or non-ionic Hydrophobic- nonpolar or non-ionic substances that repel water.substances that repel water.

fatsfats

Dissociation of WaterDissociation of Water

Water has a tendency to separate into Water has a tendency to separate into two ions: Htwo ions: H22O O H H++ + OH + OH--

Acids and BasesAcids and Bases

When there is additional HWhen there is additional H++ ions in a solution, we call the ions in a solution, we call the solution acidic.solution acidic.

When there is additional OHWhen there is additional OH-- ions in a solution, we call the ions in a solution, we call the solution basic.solution basic.

pH Scale0-14

<7 Acidic

=7 Neutral

> 7 Basic

BuffersBuffers

Substances that minimize changes Substances that minimize changes in the concentrations of Hin the concentrations of H++ or or OHOH-- in a solution. in a solution.

Buffers are found in human blood Buffers are found in human blood in order to maintain blood pH in order to maintain blood pH very close to 7.4very close to 7.4

Acid RainAcid Rain

Due to pollution of sulfur oxides Due to pollution of sulfur oxides and nitrogen oxides (mainly from and nitrogen oxides (mainly from the burning of fossil fuels), rain in the burning of fossil fuels), rain in many parts of the world is acidic.many parts of the world is acidic.

Acid Rain pH can be as low as 2Acid Rain pH can be as low as 2

This leads to incredible biological This leads to incredible biological damage, especially in lakes, damage, especially in lakes, ponds, and soil.ponds, and soil.

QUIZQUIZ

1. What type of bonds exist between water molecules?1. What type of bonds exist between water molecules? Hydrogen bondsHydrogen bonds2. The ability of water to cling to itself is due to:2. The ability of water to cling to itself is due to: CohesionCohesion3. It is usually cooler near the beach during the summer 3. It is usually cooler near the beach during the summer

because of which property of water:because of which property of water: High specific heatHigh specific heat4. Life can live underwater through the coldest winters 4. Life can live underwater through the coldest winters

because:because: ICE floatsICE floats5. The bonds that are broken when water molecules vaporize 5. The bonds that are broken when water molecules vaporize

are:are:a) ionic bondsa) ionic bondsb) hydrogen bondsb) hydrogen bondsc) polar covalent bondsc) polar covalent bondsd) nonpolar covalent bondsd) nonpolar covalent bonds

B- hydrogen bondsB- hydrogen bonds

QUIZQUIZ

6. In salt water, what is the solute?6. In salt water, what is the solute? SaltSalt7. What type of molecule does water dissolve more readily, 7. What type of molecule does water dissolve more readily,

hydrophobic or hydrophilic?hydrophobic or hydrophilic? HydrophilicHydrophilic8. Substances that have excessive H8. Substances that have excessive H++ ions are considered: ions are considered: AcidicAcidic9. A substance with a pH of 10.4 is considered:9. A substance with a pH of 10.4 is considered: BasicBasic10.10. Which of the following is considered hydrophobicWhich of the following is considered hydrophobic

a) sugara) sugarb) pastab) pastac) table saltc) table saltd) waxd) wax

D- waxD- wax