Transcript What Molecule Is Most Common In Living Cells?
Chapter 3: Water and Life Essential Knowledge 2.a.3 – Organisms must exchange matter with the environment to grow, reproduce, and maintain organization (3.13.3). 7 Properties of Water 1) 2) 3) 4) 5) 6) 7) Cohesive Adhesive High surface tension Stabilizes temperatures High heat of vaporization Expands when frozen Versatile solvent 1) Liquid Water Is Cohesive Water sticks to water. Why? • Because the polarity of water results in hydrogen bonding. Contributes to transport of nutrients (plants) 2) Liquid Water is Adhesive Water sticks to other molecules. Why? • Hydrogen bonding. Plants: • 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. Why? Hydrogen bonding. Greater surf tension than most liquids 4) Water Stabilizes Temperature Water can absorb and store a huge amount of heat from the sun. Result - climate moderation Result - organisms are able to survive temperature changes. 5) Water Has A High Heat Of Vaporization Heat of Vaporization: • The quantity of heat a liquid must absorb for 1g of it to convert to a gaseous state. Results: • Water cools organisms from excessive heat buildup. • Why? Hydrogen bonding 6) Water Expands When It Freezes The distance between water molecules INCREASES from the liquid to the solid form. Result: • Aquatic life can live under ice. Why? • Hydrogen bonding Solids and Liquids Water Benzene Floats Sinks States of Matter Solid Liquid Gas 7) Water Is A Versatile Solvent Water will form a solution with many materials. Considered the best solvent Why? • Hydrogen bonding Solvent The dissolving agent. The material in the greater quantity. Ex: • Water • Alcohols • Buffers Water is the best solvent • Why? Versatile (can dissolve MOST solutes) Solute The substance that is dissolved. The material in the lesser quantity. Ex: • Salt • Sugar • Kool-aid powder Hydrophilic Materials Materials that dissolve in water. • Hydro - water • philic - to like or love Have ionic or polar regions (polar covalent bonds) on their molecules for H+ bonds. Hydrophobic Materials that repel water. Hydro - water phobic - to fear Have non-polar covalent bonds. • Remember: In npc bonds, e- are shared evenly. Ex: • Lipids • Cell membrane components Quick Review What is cohesion? What is adhesion? Name the main reason that water possesses the properties that it does. Give an example of each of the following: • Solute • Solvent Solution Concentration Usually based on Molarity. Molarity - the number of moles of solute per liter of solution. Use mass to calculate # of molecules Moles The molecular weight of a substance in grams. One Avogadro’s number of molecules. • 6.02 X 1023 = 1 mole One Mole of each Sugar Copper Sulfate Sulfur Mercury Oxide Sodium Chloride Copper Dissociation of Water Water can sometimes split into two ions. In pure water the concentration of each ion is 10-7 M Dissociation of Water, Continued Adding certain solutes disrupts the balance between the two ions. The two ions are very reactive and can drastically affect a cell. Acids Materials that can release H+ (when dissolved in water) pH = 0-7 (6.9) Example: HCl HCl H+ + Cl- Bases Materials that can absorb H+ Often reduce H+ (by producing OH- ) pH = 7.1-14 Example: NaOH, blood (7.4-7.8), bleach Neutrals Materials that are neither acids nor bases. pH = 7 (ish) • Usually 6.5-7.4 Ex: • Urine pH Scale A logarithmic scale for showing H+ concentration pH = - log [H+] pH Scale Example: For a neutral solution: [H+] is 10-7 or - log 10-7 or - (-7) or 7 pH, cont. Acids: pH <7 etc. Bases: pH >7 etc. Each pH unit is a 10x change in H+ [H+] + [OH-] = 14 Therefore, if you know the concentration of one ion, you can easily calculate the other. Buffers Materials that have both acid and base properties. Resist pH shifts. Cells and other biological solutions often contain buffers Buffers, cont. Advantage: • Prevents damage to cell/DNA • pH changes can denature proteins Ex: • Buffers in blood keep pH around a slightly basic pH Most are acid-base pairs Summary Recognize the chemical structure of water. Relate the structure of water to its properties. Identify and discuss the unique properties of water. Calculate specific concentrations of solutions (moles). Recognize pH and the pH scale. Recognize acids, bases, and buffers.