BIOL 101 1st Edition Lecture 3 Outline of Last Lecture I Matter II Structure and Behavior of Atoms III Electrons and Energy Levels IV Chemical Bonds V Chemical Reactions Outline of Current Lecture I Importance of Water II Causes of Unusual Behaviors of Water III Unusual Properties of Water IV Aqueous Solutions and Their Properties V Acids Bases and pH VI Solute Concentration EXTRA CREDIT HW Problems VII Solute Concentration EXTRA CREDIT HW Solutions VIII pH EXTRA CREDIT HW Problems IX pH EXTRA CREDIT HW Solutions X QUIZ THURSDAY IN CLASS Current Lecture I Importance of H2O Important in living things Began life organisms made up of mostly water Water covers Earth s surface Major reason that we have life on the planet II Unusual behavior of water is caused by Hydrogen bonds o Polar covalent bonds between O and H o charge on H o charge on O o Water is attracted to water molecules and other polar or charged molecules because of charge attractions o This unusual behavior is an example of EMERGENT PROPERTIES one of the unifying themes of bio lecture 1 III Unusual properties of H2O High specific heat amount of heat in calories that is required to increase the temperature of a substance by 1 C o Doesn t easily change temperature o Heat breaks hydrogen bonds before it increases temperature o If you take out the heat to cool water down the temperature doesn t change hydrogen bonds form o Biological significance Living things resist temperature change Stabilizes ocean temperature Expands when it freezes o Ice is less dense than water ice floats on water Not usually the case with other substances Caused by hydrogen bonds In liquid form hydrogen bonds form and break often dynamic move a lot At 0 C the molecules no longer move to break and form hydrogen bonds Biological significance i Floating ice insulates the water below prevents the water from freezing solid keeps organisms in water alive o Water is the biological solvent Solution liquid that is a homogenous mix of two or more substances made of Solute substance that is dissolved Solvent liquid that dissolves the substance A cell is like a drop of water with many solutes in it The properties of water as a solvent are due to the hydrogen bonding Great solvent for solutes that are charged or polar because water is POLAR i Ex NaCl table salt easily dissolved in water H2O molecules pull the 2 ions apart and surround them Nonpolar substances do NOT dissolve in water polar and nonpolar substances do NOT mix i Ex H2O and oil don t mix water polar oil nonpolar IV Properties of Aqueous Solutions Aqueous solutions H2O is the solvent Cells are aqueous solutions so it s important to know these 2 properties o Solute Concentration the number of molecules in a given amount of solution Terms to know Mole number of grams of a substance equal to its molecular weight to find moles grams of the substance substance s molecular weight Molecular weight sum of the atomic masses of each atoms in the molecule Molar M number of moles of a solute in one liter L in a solution molarity o The concentration of substances is given in terms of Molarity because one mole of any substance has the SAME number of MOLECULES as one mole of anything else Avagadro s number 6 02 1023 V Acids Bases and pH H2O can disassociate rarely happens but important because small changes in H and OH can cause dramatic changes in the ability of biological molecules to function gives Oxygen a full negative charge from the electron that Hydrogen leaves behind when they disassociate o Pure H2O has H and OH as equal aka in balance o When acids and bases dissolve in water the balance of H and OH is shifted o Pure H2O H OH 10 7 o Acids ADD H to the solution o Bases REDUCE H holds H or donates OH o In an aqueous solution i H OH 10 14 1 If one goes down the other must go up to maintain the product of 10 14 ii If you know the concentration of one you can use the formula to find the other o pH scale scale that measures the degree of acidity on a scale of 0 14 ii Mathematically pH log H question on first exam iii pH 7 acidic iv pH neutral pure water Hydrogen 10 7 pH log 7 7 v pH 7 basic vi Each unit of pH represents a 10 fold change in H vii Most biological fluids maintain a pH of between 6 and 8 o Equations to help with pH ii pH log H iii pOH log OH iv H OH 10 14 v pH pOH 14 VI Solute Concentration Problems 1 How many grams of glucose C6H12O6 are in 1 Mole of glucose 2 How many moles of glucose C6H12O6 are in 1 Liter of a 1M solution of glucose How many moles of glucose are in 1 Liter of a 2M solution of glucose How many molecules are in each of these solutions 3 You have 1 Liter of a 1M solution of glucose C6H12O6 How many moles of fructose C5H10O5 would you need to have an equal amount of glucose and fructose molecules 4 How many grams of C4H10 are in one mole of C4H10 How many molecules of C4H10 are in one mole of it 5 How would you make a 1M solution of C4H10 VII Solute Concentration Solutions 1 C 12g H 12g O 16g 6 12 12 1 6 16 180g mol 2 1 mole of glucose in 1M solution 6 02 1023 molecules of glucose 2 moles of glucose in 2M solution 1 204 1024 molecules of glucose 3 1 mole of fructose 4 C 12g H 1g 4 12 10 1 58g mol 6 02 1023 molecules of C4H10 5 Dissolve 58 grams of C4H10 in some water and then once it has dissolved add more water until the solution is equal to 1 Liter VIII pH Problems 1 What is the mathematical definition of pH 2 What is the pH of a solution that has H 10 5M 3 If a solution has a pH of 5 what is the H What is the OH 4 If a solution has a pH of 4 what is the pOH 5 The pH of a solution is increased from 6 to 7 Is the H increased or decreased By how much 6 The pH of a solution is increased from 6 to 7 Is the H increased or decreased By how much IX ph Solutions 1 pH log H 2 pH log H pH log 10 5 pH 5 3 pH log H 5 log H 10 log H 10 5 H 10 5 H OH 10 14 10 5 OH 10 14 OH 10 9 4 pH pOH 14 4 pOH 14 pOH 10 5 The H is decreased It is decreased by 10 6 10 9 H 10 14 H 10 5 pH log H pH log 10 5 pH 5