Scientific MethodWhat is Science?-understanding natural world-study of how world works-how to apply the understandingWhat do scientists do?make observations attempt to discern patterns (from the observations)[something is easier to understand when you look for patterns in the things you learn]assume that the future is like the pastScientific Method: What are the basic steps of the method? observation…generalization or model… prediction or hypothesis(what will happen in a year?)…test this(see what happens)What is the outcome of this process?…these tests generate a new observation. You look at the data you collected and continue through the circleTerminologyHypothesis- prediction for something that has not been tested yet, best guessTheory-hypothesis has been tested many times and has been supported & has validityvery good modelLaw-nothing more than a theory that has continued to be tested and gain supportdon’t see a lot in biologywe speak of laws in terms of physics, chemistryfew in biology because the study is much newer, so still developingWhat is Biology? The study of lifeWhat is Life?This is more difficultwe don't know what exactly will happenreproductionrequires resourcescellsevolves, adaptable (responds to environment)made of organic matter**organization (complex molecules, ecosystem)**a lot of energy goes to maintaining this organization (breathing, gas exchange)development (**reproduction, growth, changes during lifetime as organism)evolve**respond to environment (this is what people use to determine weather something is alive)What are the characteristics of Life?BASIC CHEMISTRY: We are going to begin by using a reductionist approach.Scale of Nature: What are the sizes of biologically important structures Log Scale Solubility (DEMO)"Like dissolves Like" Sucrose (sugar) dissolved in waterSucrose (sugar) did not dissolve in ethanolWhat determines this?Like dissolves likeLike in terms of polarityPolar solutes dissolve in polar solventsNon-polar solutes dissolve in non-polar solventsWhat determines the polarity of a molecule?The type of bond(s) within a moleculePolarity is important biologicallyThey are the result of electrical attractions between atomsGaining, losing, or sharing as a result of valenceElectrical attraction are what is holding us togetherOpposite charges attractATOMS:Smallest unit of matter separable by normal chemical means. (chemistry definition)Smallest unit of an element, that retains all of the elements properties.An atom is composed of many smaller particles.particle mass electric chargeproton- +1 chargemass of 1 daltonneutron- 0 charge; neutralmass of 1 daltonelectron- -1 chargemass of ~0 daltonAtomic # is the number of protonsThis determines the characteristics of the elementAtomic Mass is the number of protons + neutrons (sum of the mass of all the subatomic particles)Atomic Structure:Bohr ModelThis model has electrons moving in orbitals or shells around the nucleus.Not the most accurate modelElectrons fill the shell from the inside outThe electrons always try to be in the lowest orbital or energy shell (that is closest to the nucleus).The lowest level (K)—full at 2; least energythe next level (L)His next observation was that an atom was most stable (that is unreactive) when the outer most shell (M) of electrons was full.Atoms will try to gain or lose electrons in order to fill their outer shell or valence shell.The number of electrons to be gained or lost to fill the outer shell of electrons is called the valence.Valence predicts the number of bonds that an atom will formValence electrons: the electrons in the outermost shellSTRONG BONDS:::Bonds which are the result of very strong electrical attraction, where electrons are lost or gained are called IONIC BONDS.Form when atoms completely gain or lose electronsStrongest bonds when DRYComplete removal of electronOne has too many; one has one too fewThe two oppositely charged ions now attract one anotherBonds which are the result of electrical attractions which are not so strong, where the electrons are shared are COVALENT BONDS.If shared equally—purely covalentMost common, when the two atoms are the same: H-H, C-C, O-O, C-H(an exception)Only C-H in the carbon backbone, non-polarIf shared unequally—polar covalent (charge separation)Strongest bond in water (important in biology for organic molecules within cells)POLAR COVALENT BONDS Can these bonds can be considered to grade from one to another?The force between the atoms holding them together is really the same forceOn one side, you have no sharing (have it 100%, other has 0%)On other side, you have covalent (sharing perfectly)In between, you have polar covalent!What determines the number and type of bond?Number = the valenceType = electronegativityElectronegativity: a measure of the tendency of an atom to attract a bonding pair of electronsMeasure of the attraction an atom has for electronsHow much it wants to gain or lose!Electronegativity seems to increase from left to right on periodic tableElectronegativity increases from bottoms to top on periodic tableElectronegativity & BondsIonic: when differences are 1.7 or greater, the bond is usually ionicCovalent (non-polar): when differences are of less than .5Polar covalent are between .5 and 1.7NOTE: THE NUMBER IS THE DIFFERENCE BETWEEN THEMHow do bonds influence the polarity of the molecule?Molecules which contain ionic bonds will be polarGoing to go into solution in waterMolecules which contain polar covalent bonds will be polar (with just a few exceptions)Also goes into solution in waterMolecules which contain pure covalent bonds will be non-polarWill not go into solution in water Electronegativity Weak Bonds:A bond which is the result of very weak electrical attractions between atoms on different molecules or difference parts of a large molecule bearing partial electrical charges are HYDROGEN BONDS.One atom involved must be HydrogenOccur between molecules that have polar covalent to ionic bondsThere are so many of them! QUANTITYWeak bonds: bonds which are not involved in making a substanceMOLECULES AND COMPOUNDSA molecule is: the smallest unit of a compound with the same propertiesA compound is: a substance consisting of two or more different atoms, in specific proportions, bonded together in a specific patternMolecular formula: A shorthand way to represent the types and numbers of different atoms present in a molecule.H2OCO2C6H12O6Isomers: molecules of the same
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