BIOL 1107 1nd Edition Lecture 3 Outline of Last Lecture I Quantifying Molecules II Chemical Reactions a Transfer of Energy III Why is water an efficient solvent Outline of Current Lecture I Water and Hydrogen Bonds II The pH Scale and Buffers III How Do Chemical Reactions Happen IV The 1st and 2nd Laws of Thermodynamics Current Lecture I Water and Hydrogen Bonds Ions and polar molecules stay in solution because of their interactions with water s partial charges These atoms and molecules are said to be hydrophilic Uncharged and nonpolar compounds that do not dissolve in water are said to be hydrophobic Life uses these properties to its advantage For example human skin has hydrophilic properties in order for water to be absorbed and released from the body as well as hydrophobic properties so the skin does not dissolve on contact with water Hydrogen bonding makes it possible for almost any charged or polar molecules to dissolve in water Because of hydrogen bonding there are special characteristics that form such as density For example ice is less dense than liquid water because in ice polarity only allows the molecules to get so close forming crystal lattice forms causing the ice to reach its maximum density However in liquid water the molecules are able to get closer and further apart not forming a crystal lattice structure allowing liquid to be denser II The pH Scale and Buffers The pH scale is logarithmic o greater H concentration lower pH more acidic These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute o lower H concentration higher pH more basic alkaline Buffers are compounds that minimize changes in pH III How Do Chemical Reactions Happen Chemical reactions have reactants and products Energy is the capacity to do work or supply heat Energy exists as stored potential or as an active motion Electrons have the greatest potential energy in the outermost electron shells The further the electrons are from the nucleus the more potential energy It s about POSITION of electrons across the bond IV The 1st and 2nd Laws of Thermodynamics Heat is the thermal energy transferred between objects if different temperatures The 1st Law of Thermodynamics states that energy is conserved it cannot be created or destroyed only transferred or transformed it is important to note the difference between transferred vs transformed The 2nd Law of Thermodynamics entropy disorder always increases o We have to maintain so things do not go into a state of disorder For example when we die order is no longer being maintained so our bodies go into disorder and decompose o What is meant by more order Has more potential energy more chemical bonds added thermal energy heat endothermic
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