Chapter 3: Water and Life

Essential Knowledge 2.a.3 – Organisms must exchange matter with the environment to grow, reproduce, and maintain organization ( ). 2.a.3 – Organisms must exchange matter with the environment to grow, reproduce, and maintain organization ( ).

7 Properties of Water 1) Cohesive 1) Cohesive 2) Adhesive 2) Adhesive 3) High surface tension 3) High surface tension 4) Stabilizes temperatures 4) Stabilizes temperatures 5) High heat of vaporization 5) High heat of vaporization 6) Expands when frozen 6) Expands when frozen 7) Versatile solvent 7) Versatile solvent

1) Liquid Water Is Cohesive Water sticks to water. Water sticks to water. Why? Why? Because the polarity of water results in hydrogen bonding.Because the polarity of water results in hydrogen bonding. Contributes to transport of nutrients (plants) Contributes to transport of nutrients (plants)

2) Liquid Water is Adhesive Water sticks to other molecules. Water sticks to other molecules. Why? Why? Hydrogen bonding. Hydrogen bonding. Plants: Plants: Water adheres to cell walls (helps pull water and nutrients through plant)Water adheres to cell walls (helps pull water and nutrients through plant)

Water transport in trees uses Cohesion and Adhesion

3) Water Has A High Surface Tension The surface of water is difficult to stretch or break. The surface of water is difficult to stretch or break. Why? Hydrogen bonding. Why? Hydrogen bonding. Greater surf tension than most liquids Greater surf tension than most liquids

4) Water Stabilizes Temperature Water can absorb and store a huge amount of heat from the sun. Water can absorb and store a huge amount of heat from the sun. Result - climate moderation Result - climate moderation Result - organisms are able to survive temperature changes. Result - organisms are able to survive temperature changes.

5) Water Has A High Heat Of Vaporization Heat of Vaporization: Heat of Vaporization: The quantity of heat a liquid must absorb for 1g of it to convert to a gaseous state.The quantity of heat a liquid must absorb for 1g of it to convert to a gaseous state. Results: Results: Water cools organisms from excessive heat buildup.Water cools organisms from excessive heat buildup. Why?Why? Hydrogen bonding Hydrogen bonding

6) Water Expands When It Freezes The distance between water molecules INCREASES from the liquid to the solid form. The distance between water molecules INCREASES from the liquid to the solid form. Result: Result: Aquatic life can live under ice.Aquatic life can live under ice. Why? Why? Hydrogen bondingHydrogen bonding

Solids and Liquids WaterBenzene Floats Sinks

SolidLiquid Gas States of Matter

7) Water Is A Versatile Solvent Water will form a solution with many materials. Water will form a solution with many materials. Considered the best solvent Considered the best solvent Why? Why? Hydrogen bonding Hydrogen bonding

Solvent The dissolving agent. The dissolving agent. The material in the greater quantity. The material in the greater quantity. Ex: Ex: WaterWater AlcoholsAlcohols BuffersBuffers Water is the best solvent Water is the best solvent Why? Versatile (can dissolve MOST solutes)Why? Versatile (can dissolve MOST solutes)

Solute The substance that is dissolved. The substance that is dissolved. The material in the lesser quantity. The material in the lesser quantity. Ex: Ex: SaltSalt SugarSugar Kool-aid powderKool-aid powder

Hydrophilic Materials Materials that dissolve in water. Materials that dissolve in water. Hydro - waterHydro - water philic - to like or lovephilic - to like or love Have ionic or polar regions (polar covalent bonds) on their molecules for H + bonds. Have ionic or polar regions (polar covalent bonds) on their molecules for H + bonds.

Hydrophobic Materials that repel water. Materials that repel water. Hydro - water Hydro - water phobic - to fear phobic - to fear Have non-polar covalent bonds. Have non-polar covalent bonds. Remember: In npc bonds, e- are shared evenly.Remember: In npc bonds, e- are shared evenly. Ex: Ex: LipidsLipids Cell membrane componentsCell membrane components

Quick Review What is cohesion? What is cohesion? What is adhesion? What is adhesion? Name the main reason that water possesses the properties that it does. Name the main reason that water possesses the properties that it does. Give an example of each of the following: Give an example of each of the following: SoluteSolute SolventSolvent

Solution Concentration Usually based on Molarity. Usually based on Molarity. Molarity - the number of moles of solute per liter of solution. Molarity - the number of moles of solute per liter of solution. Use mass to calculate # of molecules Use mass to calculate # of molecules

Moles The molecular weight of a substance in grams. The molecular weight of a substance in grams. One Avogadro’s number of molecules. One Avogadro’s number of molecules X = 1 mole 6.02 X = 1 mole

One Mole of each Sulfur Sugar Copper Sulfate Mercury Oxide Copper Sodium Chloride

Dissociation of Water Water can sometimes split into two ions. Water can sometimes split into two ions. In pure water the concentration of each ion is M In pure water the concentration of each ion is M

Dissociation of Water, Continued Adding certain solutes disrupts the balance between the two ions. Adding certain solutes disrupts the balance between the two ions. The two ions are very reactive and can drastically affect a cell. The two ions are very reactive and can drastically affect a cell.

Acids Materials that can release H + (when dissolved in water) Materials that can release H + (when dissolved in water) pH = 0-7 (6.9) pH = 0-7 (6.9) Example: HCl Example: HCl HCl H + + Cl - HCl H + + Cl -

Bases Materials that can absorb H + Materials that can absorb H + Often reduce H + (by producing OH - ) Often reduce H + (by producing OH - ) pH = pH = Example: NaOH, blood ( ), bleach Example: NaOH, blood ( ), bleach

Neutrals Materials that are neither acids nor bases. Materials that are neither acids nor bases. pH = 7 (ish) pH = 7 (ish) Usually Usually Ex: Ex: UrineUrine

pH Scale A logarithmic scale for showing H + concentration A logarithmic scale for showing H + concentration pH = - log [H + ] pH = - log [H + ]

pH Scale

Example: For a neutral solution: [H + ] is or - log or - (-7) or 7

pH, cont. Acids: pH <7 etc. Acids: pH <7 etc. Bases: pH >7 etc. Bases: pH >7 etc. Each pH unit is a 10x change in H + Each pH unit is a 10x change in H + [H + ] + [OH - ] = 14 [H + ] + [OH - ] = 14 Therefore, if you know the concentration of one ion, you can easily calculate the other. Therefore, if you know the concentration of one ion, you can easily calculate the other.

Buffers Materials that have both acid and base properties. Materials that have both acid and base properties. Resist pH shifts. Resist pH shifts. Cells and other biological solutions often contain buffers Cells and other biological solutions often contain buffers

Buffers, cont. Advantage: Advantage: Prevents damage to cell/DNAPrevents damage to cell/DNA pH changes can denature proteinspH changes can denature proteins Ex: Ex: Buffers in blood keep pH around a slightly basic pHBuffers in blood keep pH around a slightly basic pH Most are acid-base pairs Most are acid-base pairs

Summary Recognize the chemical structure of water. Recognize the chemical structure of water. Relate the structure of water to its properties. Relate the structure of water to its properties. Identify and discuss the unique properties of water. Identify and discuss the unique properties of water. Calculate specific concentrations of solutions (moles). Calculate specific concentrations of solutions (moles). Recognize pH and the pH scale. Recognize pH and the pH scale. Recognize acids, bases, and buffers. Recognize acids, bases, and buffers.