BIOLOGY 111 1st Edition Lecture 3 Outline of Last Lecture I. MethodsII. ReasoningsIII. ExperimentationIV. Scientific TheoryV. Overview of Chemistry and Physics Outline of Current Lecture I. Continue Chemistry ReviewII. BondsIII. Chemical ReactionsIV. Properties of waterCurrent Lecturecontinue chemistry • covalent bonds form when atoms share pairs of valence electrons◦ equal pairing between two atoms◦ single (ex. hydrogen) - one bond formed by sharing electrons between two atoms◦ double (ex. oxygen) - two bonds formed by sharing electrons between two atoms◦ triple (ex. nitrogen) - three bonds formed by sharing electrons between two atoms• non-polar covalent bonds - equal sharing of electrons b/c each atom have same electronegativity (tug-of-war)• polar covalent bonds - unequal sharing of electrons b/c different electronegativity between the two atoms *(common in water between hydrogen and oxygen (higher affinity), therefore oxygen pulls the hydrogens more than hydrogen pulls)*Oxygen is one of the most electronegative of all the elements, attracting shared electrons more stronglyelectronegativity - affinity for electrons (the differences dictate location of electrons)• electrons are not always shared evenly between atoms• some attract shared electrons more readily than othersThese 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.[partial positive (push electrons away) and negative (pull electrons towards)]• extreme differences cause the gain and loss of electrons between atoms by pulling them (forming ionic bonds)Ion - a charged atom (or molecule)◦ anion (-) the atom that gains an electron◦ cation (+) the atom that loses an electron*also applies to entire molecules that are electrically chargedIonic bond - attraction between oppositely charged (cations and anions) atoms, or ions.*can be formed even if there is no electron transfer from one to the otherIonic bonds vs covalent bondsionic - very strong in air/vacuum but weak in aqueous solutioncovalent - very strong in generalIonic compounds (salts) - compounds formed by ionic bonds*salts often occur in nature as crystals◦ does not consist of molecules, unlike a covalent compound◦ not all salts have equal number of cations and anionsHydrogen bonds - non-covalent attraction between a hydrogen and an electronegative atombetween polar molecules these are weak but important [between two partially charged atoms (H being partial +)]*in living cells the electronegative atom is usually oxygen (for water) or nitrogen (for ammonia) atomsVan der Waals interactions: are individually weak and occur only when atomsand molecules are very close together causing momentary electrical asymmetry in molecules*although they are very weak interactions, there are so many that they, overall, make a huge impact *very temporary (causing temporary connection b/c of temporary imbalance of charges *temporary partial positive/negative charges (that attract) for temporary interactionsex. gecko holding onto a wall or DNA and same concept as applied to Velcrodepicting chemical bonds: use structural formula or lewis dot structurebody organizes new molecules, if doesn't recognize it, it gets rid of itso drugs, natural and synthetic, made to mimic compounds already in the body so body can recognize it, binds it, and produces the desirable effectChemical reactions - making and breaking of chemical bonds, leading to changes in the composition of matter• we are given starting materials, known as reactants.• through a reaction, our reactant (starting material) is converted into productChemical equilibrium - the exact point at which reactions offset one another • when the forward and reverse reaction rates are equal• this does not mean reactants and products are equal in concentration, but that they have stabilized at a particular ratioChapter 3 (Water)life depends on the unusual properties of "liquid" water (everything in the body occurs in aqueous/liquid form)where there is water, there may be life- surface of mars and earth each have sediment and similar composition- current conditions of mars don't suggest life, but suggest there may have beenwaters unusual properties emerge from molecular characteristics There are FOUR emergent properties of water1. Cohesive - stick to itself, to hold itself together, this is due to hydrogen bonding (surface tension: measure of difficulty in stretching/breakingthe surface of a liquid) 2. Adhesive - sticks to other molecules [clinging of one molecule to another (water drop to a leaf or to a spider web)]3. Moderation of temperature by water - water moderates air temperature by absorbing heat from warmer air and releasing storedheat to cooler air (water resists temperature change, and is able to release and absorb a lot of heat without changing its own temperature)A. Heat - form of energy (total kinetic energy) and based on the volume ex. ocean holds more heat than glass of water B. Temperature- measure of "heat" or energy (average kinetic energy), and does not depend on volume *ex. ocean and glass of water have the same temperature a. Specific heat - water resists temperature change, water absorbs/releases heat with little change to actual temperature *helps to moderate coastal environmentsb. evaporative cooling (heat of vaporization) - amount of energy to convert liquid to gas (580 cal : 1 gram at room temperature)to evaporate, hydrogen bonds must break, as evaporates, heat is removed (evaporative cooling)*will be burnt more by steam than hot water itself4. Expansion upon freezing - instead of solidifying, like most other materials, water expands• allows ice to float, water is one of few substances that is less dense as a solid than as a liquid• at temperatures above 4 degrees Celsius, water behaves like other liquids, expanding as it warms, contracting as it cools • most dense at 4 degrees Celsius• between 4 and 0 degrees Celsius, water expands as it freezes rather than contracting as it would if above 4 degrees CelsiusIce : Hydrogen bonds are stable (holds it together firmly)liquid water: hydrogen bonds break and reform (less stable)Water as a SolventWater molecules, b/c of polarity, make a really good solvent solution - mixture of two or more substancessolvent - the dissolving agentaqueous solution - when water acts as the solventhydration shell - the sphere of water molecules around