NYA Lecture 2: Properties of Water PDF

NYA Lecture 2 Properties of Water Properties of Water Chemistry C/Carbon: Forms the basic structure of most biomolecules H/Hydrogen: water – also involved in 96% of acid/base reactions all living Oxygen: water – also breathing...

NYA Lecture 2 Properties of Water Properties of Water Chemistry C/Carbon: Forms the basic structure of most biomolecules H/Hydrogen: water – also involved in 96% of acid/base reactions all living Oxygen: water – also breathing mater N/Nitrogen: DNA, Proteins S/Sulfur: amino acids P/Phosphorus: cell membranes Ca/Calcium: 4% of all nerves and muscles living K/Potassium: nerves and mater muscles 1  Properties of Water Fig 2.12 Properties of Water Fig 2.10 2  Properties of Water Importance of Water  ~70% of our planet  Most of life developed in water  First terrestrial organisms took their watery environment with them.  We don’t live in water – But a significant amount in our bodies. Bonds Ionic bonds: No sharing – electron is “removed” Fig 2.12 Covalent bonds: molecules share their e Non-polar covalent: two molecules of same element Polar covalent: electrons not shared evenly Fig 2.10, Properties of Water O2 is more electronegative than H Electronegativity of an atom pulls the shared electrons towards itself. Fig 2.11, 3.2  Makes O2 slightly more –ve  H2O - asymmetrical – formed of polar covalent bonds Fig 2.11 3  Properties of Water Hydrogen bonds: Bonds between molecules are hydrogen bonds. These are weak bonds. Because of this H2O is fluid – bonds broken and remade all the time. Due to the above properties water is special Properties of Water Fig 2.14 4  Properties of Water Properties of Water 1. Water’s Cohesion  Many organisms depend on the cohesion of H2O  Water molecules stick together. Bonds broken and formed all the time– very fast  At any given time most H2O molecules are bound  This creates surface tension Fig 3.3, 3.4 Properties of Water Fig 3.3 5  Properties of Water 2. Water moderates temperature Temperature is due to the speed of molecules, the faster the speed the higher the higher the heat Specific Heat = Amount of heat that must be absorbed or lost for 1g of substance to change it’s temp. by 1C  H2O has a high specific heat  When water is heated some of the heat goes to break the H bonds, so the temp doesn’t rise very fast.  When water is cooled some H bonds are formed, giving off heat and keeping the temp higher for longer Properties of Water So what??  Large body of H2O absorbs heat during day, gives off heat at night. Coastal areas milder than inland  Stabilizes temp of the ocean  Cells of many organisms mostly H2O – helps resist changes in temp. Fig 3.5 6  Properties of Water Evaporative Cooling:  As water is heated its molecules gain energy.  The most excited ones at the surface that have absorbed the most energy escape into the air taking their heat energy with them and what is left is cooler Eg. Humans and sweating Properties of Water 3. Ice is less dense than water  When H2O freezes all H bonds become completed ice crystals and heat is released Fig 3.6  Ice is less dense than water ice floats  Ice insulates H2O below allows survival of aquatic organisms See Figs 7  Properties of Water Eg. Diving in Canada: summer deeper = colder winter deeper = warmer Fig 3.6 Properties of Water Ice fishing 8  Properties of Water 4. Water – The Solvent Of Life- pH Sugar cube in H2O dissolves Solution contains uniform mixture of sugar and water Solute: substance to be dissolved Solvent: substance used to dissolve solute When water is solvent aqueous solution pH: Too much H can change pH  Some aqueous solutions can have imbalances in H+ or OH- conc Fig 3.8, 3.11 Properties of Water Fig 3.8 9  Properties of Water Solution with more OH: basic Solution with more H: acidic Solution with OH = H: neutral Changes in pH are bad in biology Fig 3.11 Properties of Water  Acid rain pH 5.6 – fossil fuel compounds that react with water vapour in atmosphere and give acidic rain 10  Properties of Water Acid rain detrimental to Fig 3.13 coral reefs Properties of Water Acid rain also bad for aquatic communication in both fresh and salt water 11  Properties of Water Organic Chemistry 3 characteristics: 1) All organic molecules contain carbon C  C can form 4 covalent bonds Fig 4.3  C commonly forms chains by bonding with itself 2) Built of smaller molecules  Carbon chains attached together in different configurations.  Forms the “backbone” of most organic molecules Fig 4.5, 4.9 3) Form determines function 12 Properties of Water Fig 4.3 Properties of Water Fig 4.5 13 Properties of Water Fig 4.9 Properties of Water Fig 4.9 14  Properties of Water Biomolecules:  Made of different units  Long strings of identical or similar molecules covalently bonded together  These macromolecules are also called polymers  Monomer is one of the units Think of a train: The train = a polymer The train cars = monomers Chemical methods used to make & break polymers are always same Properties of Water Fig 5.2 15  Properties of Water Making Polymers (dehydration reaction): Lose a H2O Breaking Polymers (Hydrolysis) Add a H2O Fig 5.2 The 4 main classes of Biomolecules 1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic Acids 16