Campbell Biology 9th Edition Chapter 3 Notes 426d6s

Concept 3.1: WATER BOND  Polar Covalent Bonds O is more electronegative  polar molecule: unequal distribution of overall charge  H & O are held together by polar covalent bond  2 water molecules are together by Hydrogen Bond fragile 1/20 strong as covalent bond form/break a lot Concept 3.2: 4 EMERGENT PROPERTIES OF H2O  Cohesion  hydrogen bonds hold substance together  ex. transport of water and mineral up a plant against gravity  Adhesion: clinging of one substance to another  ex. water clings on to plant’s cell wall when traveling up against gravity  Surface Tension: a measure of how difficult it is to stretch of break the surface of a liquid  water has greatest surface tension  water and air in ordered arrangement hydrogen bonds created a film on top  Moderation of Temperature by water  water moderates air temp.  by absorbing warm heat from air and releasing stored “cold” heat into the air  Heat and Temperature  kinetic energy: energy of motion  heat: form of energy a measure of the matter’s TOTAL KINETIC ENERGY (depends on matter’s volume)  temperature: heat intensity that represents the AVERAGE KINETIC ENERGY (doesn’t depend on matter’s volume)  heat es warm to cold till same temperature  calorie amount of heat it takes to raise/release 1 g of water by 1 ° C  joules…1 cal=4.18 J  Water’s high specific heat (unusually high)  specific heat: amount of heat that must be absorbed or lost for 1 g of water to change temp by 1 °C 

specific heat of water  1 cal/g °C

 alcohol has lower specific heat..also iron pot will heat up faster than the water in it  water will change its temp less when it absorbs or loses heat  heat absorbed break Hydrogen bonds heat released form Hydrogen bonds  Evaporative Cooling  molecules of liquid stay together due to attraction  vaporization/evaporation: liquid to gas  Heat of Vaporization: quantity of heat a liquid must absorb for 1 g of it to be converted from liquid to gas  emergent property  because of hydrogen bonds breaking  Evaporative cooling: hottest molecules going to be gas  Floating of Ice on liquid water  water expands when it solidifies due to hydrogen bonding (molecules moving too slow to break H bonds)  4°C and above water expands as it warms and contract as it cools  0°C  crystalline lattice “lock” (each H bonded to 4 partners)  H bonds keep molecules are “arms length” far apart  makes ice 10% less dense, 10% fewer molecules than H2O  4 °C water’s greatest density  Water: The Solvent of Life  Solution: homogenous mixture or 2 or more substances (ex. sugar in water)  Solvent: dissolving agent of a solution  Solute: the stuff that is dissolved

   

Aqueous solution: water is the solvent. water is NOT the universal solvent (ex. doesn’t dissolve our cells)…water IS the solvent of LIFE hydration shell: sphere of water molecules around each dissolved ion hydrophilic and hydrophobic substances  hydrophilic: affinity for water…water loving  colloid: stable suspension of fine particles in a liquid (ex. large cells that don’t dissolve in water)  hydrophobic: repel water..water fearning  nonionic and nonpolar (ex. cell membranes)  Solute Concentration in Aqueous Solutions  molecular mass: sum of all the atoms in a molecule  always use moles…because weighing our small numbers is not practical  substances can have difference mass but same # of molecules (6.02e23)  to make 1 mol of sucrose dissolved in water324 g of sucrose + 1 L of water = 1 M of sucrose solution  Molarity: moles of solute per liter of solution Concept 3.3: Acids and Bases  H atom in bond between 2 water molecules …shift from 1 h2o to the other….leaves electron behind...transfers H+  h2o that gained a H+ is hydronium ion (H3O+) ….h2o that lost H+ is hydroxide ion (OH-)  H+ ion never exists alone associated with water or hydronium ion  H+ and OH- are very reactive  changes affect protein and other molecules  Acids and bases  acids dissolve in water…donate H+….removes OH- forming water  bases reduce H+ concentration by accepting H+ ions or dissociating (NaOH Na + OH) both making water  neutral solution: H concentration and OH concentration is equal  in reversible reaction fixed ratios (weak base= ammonia) (weak acid= carbonic acid)  pH scale  at 25°C…*H+][OH-]= 10-14  pH= -log[H+]  pH declines as H+ concentration increases  each pH unit represent 10 fold difference in H+ ions and OH-ions  pH 3 to pH 6 means 1000 times difference  Buffers  pH of human blood= 7.4  stabilizes pH  accepts H ions when in excess and donates H ions to the solution when they have been depleted  buffer solution = weak acid + corresponding base  CO2+H2O=H2CO3  HCO3+H  when H rise…HCO3 removes H ions …forming H2CO3  Acidification  25% of CO2 produced by human activity is absorbed by the ocean  CO2 dissolves in seawater forms carbonic acid lowers pH ocean acidification  acid precipitation= rain,snow, fog with pH lower than 5.2