Chapter 2: Contd…… The Chemical basis of LifeObjectives:Chemical ReactionsQuantifying MoleculesSlide 5How Do Chemical Reactions Happen?What Is Energy?Slide 8Slide 9Heat and the First Law of ThermodynamicsSlide 11What Makes a Chemical Reaction Spontaneous?Slide 13Slide 14The Second Law of ThermodynamicsGibbs Free-Energy ChangeSlide 17Slide 18Temperature and Concentration Affect ReactionsSlide 20Slide 21Slide 22Slide 23The Importance of CarbonSlide 25Functional Groups: Determinants of Chemical BehaviorSlide 27Chapter 2: Key Concepts coveredSlide 29© 2011 Pearson Education, Inc. Chapter 2: Contd……The Chemical basis of Life√ 2.1 Atoms, ions, molecules  the building blocks…What Are the Chemical Elements That Make Up Living Organisms?How Do Atoms Bond to Form Molecules?√ 2.2 What Properties of Water Make It So Important in Biology?•2.3 Chemical reactions, chemical energy•2.4 The importance of Carbon, Functional groups© 2011 Pearson Education, Inc.Objectives:•Chapter 2 – review some of the basics of inorganic chemistry•Chapters 3-6: deals with organic chemistry and biochemistry- Identify major differences among the 4 main types of biomolecules- Recognize what functional groups are and how they can modify the general properties and function of organic/ biomolecules- Use the above goals to predict how various structural modifications can affect the behavior (function) of macromolecules/ biomolecules© 2011 Pearson Education, Inc.Chemical Reactions•Chemical reactions occur when:1. One substance is combined with another. –Atoms are rearranged in molecules, or small molecules combine to form larger molecules. 2. One substance is broken down into another substance. –Molecules are split into atoms or smaller molecules. •In most cases, chemical bonds are broken and new bonds form. Chemical reactions have reactants and products. For example:CO2(g) + H2O(l)  H2CO3(aq)© 2011 Pearson Education, Inc.Quantifying Molecules•The molecular weight of a molecule is the sum of the mass numbers of all the atoms in the molecule. Example: water 18g•One mole, or 6.022  1023 molecules, has a mass equal to the molecular weight expressed in grams.•The concentration of a substance in a solution is typically expressed as molarity (M), which is the number of moles per liter.A solution is a substance (solute) dissolved in a liquid (solvent). Many important biochemical reactions occur in aqueous solutions.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.How Do Chemical Reactions Happen? •Chemical equilibrium occurs when the forward and reverse reactions proceed at the same rate and the quantities of reactants and products remain constant.•Consider the following reaction at equilibrium: CO2 + H2O ↔ H2CO3. What would be the effect of adding additional H2CO3?H2O (l)  H2O (g)Endothermic reactions must absorb heat to proceed, but exothermic reactions release heat.© 2011 Pearson Education, Inc.What Is Energy? Energy is the capacity to do work or supply heat. This capacity exists in one of two ways—as a stored potential or as an active motion.Stored energy is called potential energy. An object’s position determines its ability to store energy. For example:Electrons in an outer shell (farther from the positively charged nucleus) have more potential energy than do electrons in an inner shell.Potential Energy and Kinetic Energy:© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.•The energy of motion or movement is called kinetic energy.•Molecules have kinetic energy because they are constantly in motion. •The kinetic energy of molecular motion is called thermal energy. The temperature of an object is a measure of how much thermal energy its molecules possess.Low-temperature objects have slower molecules than high-temperature objects. [If an object has a high temperature, its molecules are moving rapidly.]© 2011 Pearson Education, Inc.Heat and the First Law of Thermodynamics•Heat is the thermal energy transferred between objects of different temperatures.•There are many forms of potential energy and kinetic energy, and energy can change from one form to another. •The first law of thermodynamics states that energy is conserved—it cannot be created or destroyed, but it can be transferred or transformed.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.What Makes a Chemical Reaction Spontaneous? Chemical reactions are spontaneous if they proceed on their own, without any continuous external influence such as added energy.•The spontaneity of a reaction is determined by two factors:1. The amount of potential energy (H)–Products of spontaneous reactions have less potential energy than the reactants.Exothermic reaction© 2011 Pearson Education, Inc.Why are some reactions exothermic?© 2011 Pearson Education, Inc.2. The degree of orderProducts of spontaneous reactions are less ordered than the reactants.Entropy (S) is the amount of disorder in a group of molecules.The second law of thermodynamics states that entropy always increases.© 2011 Pearson Education, Inc.The Second Law of Thermodynamics•Entropy (S) is the amount of disorder in a group of molecules.•The second law of thermodynamics states that entropy always increases. •In general, physical and chemical processes proceed in the direction that results in lower potential energy and increased disorder (increased entrophy).© 2011 Pearson Education, Inc.Gibbs Free-Energy Change•The Gibbs free-energy change (ΔG) determines whether a reaction is spontaneous or requires energy.ΔG < 0 is an exergonic spontaneous reaction.ΔG > 0 is an endergonic reaction that requires energy input.ΔG = 0 is a reaction that is at equilibrium.•Difference in Potential energy between reactants and product = ΔH•When the products are less ordered than the reactants, ΔS is positiveΔG = ΔH - T ΔS© 2011 Pearson Education, Inc.A reaction can be non spontaneous at low temp, butspontaneous at high temperature. WHY?Some exothermic reactions are non spontaneous. Explain?ΔG = ΔH - T ΔS© 2011 Pearson Education, Inc.Ice melts spontaneously at room temperature, even though the process is endothermic. How is this possible?© 2011 Pearson Education, Inc.Temperature and Concentration Affect Reactions•Breaking and forming bonds depends on collisions between substances.–This allows electrons to interact.•The rate of a reaction depends upon the number of