BIOL 120 1st Edition Lecture 4 Outline of Last Lecture II Basic Atomic Structure a Matter Element Atoms Protons Neutrons Electrons Molecules Energy Chemical Energy Thermodynamics Atomic Number Atomic Mass Isotope III Chemical Bonds a Valence electrons Valence Chemical Reaction Covalent Bond Ion Cation Anion Ionic Bond IV Representing Molecules a Molecular formulas Structural formulas Ball and stick models Space filling models CPK coloring models Outline of Current Lecture II Water a Hydrogen bonds hydrophilic hydrophobic cohesion adhesion III Reactions a Acid base salt buffer chemical equilibrium endothermic reaction exothermic reaction Redox oxidation reduction IV Energy a Energy potential energy kinetic thermal energy heat first law of thermodynamics Gibbs free energy change exergonic endergonic V Some key terms to know a Solution solvent solute aqueous solution molecular weight molarity VI Chemical Building Blocks start of chapter 3 a Organic compound isomer structural isomer stereoisomer enantiomer Current Lecture II Water 1 It s single most important chemical property is that it can form hydrogen bonds 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 A This is the weak bond between the partially negative O atoms and partially positive H atoms of two water molecules 2 It is a great solvent A This is because the covalent bonds in water are polar can bond to other atoms i Oxygen has a partial negative charge a Valance 2 bonds to form ii Hydrogen has a partial positive charge a Valance 1 B Hydrogen bonds the weak electrical attractions between the partially negative oxygen of one molecule and the partially positive hydrogen of a different water molecule i can also form between a water molecule and any other polar molecule 3 Water and Hydrogen bonds A Hydrogen bonds make it possible for almost any polar or charged molecule to dissolve in water i Hydrophilic can dissolve water loving i e sugar a ii Hydrophobic uncharged and nonpolar compounds that repel from water i e oil fat a 4 Structure and Properties of water A Unique because small size bent shape highly polar covalent bonds overall polarity B Properties cell structure and function depend on these i Cohesive binding between like molecules a due to hydrogen bonds holding the substance together b it can resist rupturing when stretched high surface tension 1 i e insects or leaves floating on the surface of water c This property allows for water to pull up from the roots to stems and leaves 1 i e First Nutrients that the tree needs dissolve into the water Cohesion Allows water to overcome gravity transportational pull i When hot plants transpiration loss of water from outer part of the plant holes in leaves causes plants to wilt but cools the temp of the plant due to evaporation of water ii Adhesive Binding between unlike molecules iii Denser as a solid than a liquid expands as it changes from a liquid to a solid iv Ability to absorb large amounts of energy a can do this because it has a high specific heat high heat of vaporization and can stabilize its temperature b Hydrogen bonds allow water to stabilize c it can absorb or release large amounts of heat with very slight changes in temperature this is how water protects cells from their own metabolic heat III Reactions A pH 1 expresses proton concentration in a solution i Pure water 7 ii Acids 7 a a substance that increases H concentration in a solution iii Bases 7 a a substance that reduces H concentration of a solution 2 pH scale i change in one unit of pH 10X change in H concentration a i e pH 4 pH 5 10X b pH 4 pH 6 100X ii Salt a reaction between an acid and a base iii Buffer a compound that minimizes changes in pH found in the human body for homeostasis 3 Chemical reactions i occur when a one substance is combined with another atoms are rearranged b one substance is broken down into another molecules are split into atoms or smaller molecules i e aerobic respiration ii Reactions have reactants and products iii Chemical equilibrium occurs when the forward and reverse reactions proceed at the same rate and the quantities of reactants and products remains constant iv Endothermic reaction need to absorb heat to react v Exothermic reaction release heat during a reaction vi Redox during some chemical reaction electrons can be transferred from one atom to another while still retaining the energy of their position in the atom a Oxidation loss of an electron b Reduction gain of an electron vii Spontaneity of a chemical reaction is deterimined by a the amount of potential energy b the degree of order viii Temperature and concentration affect reactions a Higher temperature more collisions faster reaction b Higher concentration more collisions faster reaction c Lower temperature less collisions slower reaction d Lower concentration less collisions slower reaction IV Energy 1 What is it A Energy the capacity to do work or supply heat i Potential energy stored energy an object s position determines its ability to store energy a i e electrons in the outer shell have more potential energy than electrons in an inner shell ii Kinetic thermal energy the energy of movement that is measured as a temperature 2 Heat and First Law of Thermodynamics A Heat the thermal energy transferred between objects of different temperatures B First Law of Thermodynamics energy is conserve it cannot be created or destroyed but it can be transferred or transformed i i e photosynthesis changes light energy into chemical energy 3 Gibbs Free Energy Change A Gibbs free energy change G determines whether a reaction is spontaneous or requires energy i G 0 an exergonic spontaneous reaction releasing energy ii G 0 endergonic reaction requires energy input iii G 0 a reaction at equilibrium V Some key terms to know 1 Solution a liquid that is a homogeneous mixture of two or more substances 2 Solvent the dissolving agent of a solution i e water 3 Solute the substance that is dissolved i e sugar 4 Aqueous solution a solution in which water is a solvent 5 Molecular weight sum of weights of all the atoms in a molecule 6 Molarity the number of moles unit for substance measure of solute per liter of solution VI Chemical Building Blocks 1 Importance of Carbon A most versatile atom on earth i has 4 valence electrons it can use to make many bonds ii can form an almost limitless array of shapes using single and double bonds B