Scientific Method and Life 08 25 2014 What is Science A body of knowledge An approach to understanding nature National Academy of Sciences definition o Use of evidence to construct testable explanations and predictions of natural phenomena as well as the knowledge generated through this process What do Scientists Do Make observations Attempt to see patterns from observations Assume that the future is like the past o Scientists are not fully sure about anything Scientific Method Observation Generalization Model Hypothesis Prediction Test Hypothesis Results reject or support hypothesis o Use it to go back to beginning more observations Not all scientists follow the step by step ex Some just observe some are just model makers etc Collaborative process You can ONLY do science on phenomena that you can observe either directly or indirectly What Happens as a Result of the Method Terminology o Hypothesis educated guess to support Tested with experiments OR more observations Model with very little support o Theory have broad base of evidence coming from several different sources agreeing on how nature works Explanation that has been tested over and over again and is always supported o Law come about when we make observations from phenomena the same thing happens over and over again ex Volume increases Pressure decreases What is Biology Study of Life What is Life o All living things Are organized Use energy to maintain organization Grow and Develop Reproduce Evolve change through time Respond to stimuli environment maintain homeostasis Scale of Nature What scales are biologists interested in Atomic 10 8 meters Community Ecosystem 10 6 meters Approaches to Biology Reductionist Approach break things down and try to isolate them into small parts and explain them one part at a time Holistic Approach interactions among large scale phenomena Basic Chemistry What Determines Solubility Like dissolves like Like in terms of polarity 08 25 2014 o Polar solutes dissolve in polar solvents o Non polar solutes dissolve in non polar solvent Atom Smallest unit of matter separable by normal chemical means Smallest unit of matter that retains all properties of an element Biologically Why are Atoms Important Organisms are composed largely of 11 basic elements Value for an average human 118 63 What s the difference between those chemicals and you Subatomic Particles Particles Mass Charge Proton 1 dalton 1 Neutron 1 dalton 0 Electron 0 dalton 1 Atomic Number and Mass Atomic Number the number of protons in an atom Atomic Mass number of protons and neutrons in an atom approx Element P N E A AM Hydrogen 1 proton 0 neutrons 1 electron Atomic of 1 Atomic mass of 1 Helium p 2 n 2 e 2 A 2 AM 4 Carbon p 6 n 6 e 6 A 6 AM 12 Carbon 14 p 6 n 8 e 6 A 6 AM 14 Nitrogen p 7 n 7 e 7 A 7 AM 14 Calcium 2 p 20 n 20 e 18 A 20 AM 40 Valence The number of electrons that need to be gained or lost to fill the outer shell of electrons Innermost shell K can only hold 2 electrons Valence also predicts the number of bonds that an atom will form Middle shell L can hold 8 electrons The outermost shell M can hold 8 electrons Nitrogen has an atomic of 7 how many electrons are in its outer shell o 5 Atom with atomic 16 has a valence of What Determines Polarity The types of bonds within molecules o 2 Chemical Bonds Ionic Bonds Form when atoms gain lose or share electrons They are the result of electrical attractions between atoms Form when atoms completely gain and lose electrons Strongest bonds when dry Covalent Bonds Form when atoms share electrons Strongest bond in water If shared equally covalent If shared unequally polar covalent Are Covalent Polar Covalent and Ionic Bonds really different bonds Forces are the same but sharing is different What determines the number and type of chemical bonds Number Number Type Electronegativity Electronegativity Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons Measure of the attraction an atom has for electrons Electronegativity and Bonds Ionic o When difference is 1 7 or greater the bond is usually ionic Covalent Non Polar o When the difference is less than 0 5 Polar Covalent o When the difference is btwn 0 5 and 1 7 How do bonds influence the polarity of a molecule Molecules which contain ionic bonds will be polar Molecules which contain many polar covalent bonds will be polar with few exceptions Molecules which contain many covalent bonds will be non polar Bonds which are not involved in making a compound Weak Bonds Hydrogen Bonds Weak attractions between atoms on different molecules or different parts of a large molecule Occur between molecules that have polar covalent to ionic bonds Always involve Hydrogen SIMPLY H N H F H O Molecules and Compounds Molecules and Compounds 08 25 2014 Compound Molecule o Substance consisting of two or more different atoms in specific proportions bonded together in a specific pattern o Smallest unit of compound that retains all chemical and physical properties of the compound Molecular Formulas Water H2O Carbon Dioxide CO2 Glucose C6H12O6 Isomers Molecules with the same molecular formula but a different arrangement of atoms Glucose Galactose and Fructose are isomers all C6H12O6 Structural Isomers two substances having the same molecular formula but different physical and chemical properties because the arrangement of their component atoms is different Cis trans Isomers Cis isomers and trans isomers often have different physical properties Differences between isomers in general arise from the differences in the shape of the molecule or the overall dipole moment Enantiomers each of a pair of molecules that are mirror images of each other Molecular Weight The sum of the atomic masses for all the atoms in a molecule o H2O 1 2 16 18 Daltons o CO2 16 2 12 44 Daltons o C12H22O11 12 12 22 16 11 342 Daltons Gram Molecular Weight The mass of a substance equal to its molecular weight in grams Contains a constant number of molecules Avogadro s Number o 6 023 x 10 23 molecules Moles and Molar Concentrations 1 Mole the mass of a substance equal to its gram molecular 1 molar solution a solution containing 1 mole of a substance per 1 weight liter of solution Properties of Water Cohesive and Adhesive High Specific Heat Takes a lot of energy to change temperature of water High Heat of Vaporization takes a lot of energy Less Dense as a Solid than a Liquid Good Solvent for Polar Molecules Universal Solvent Dissociation Many molecules come
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