Unit 1 Definition of Science o The use of evidence to construct testable explanations and predictions of natural phenomena as well as the knowledge generated through this process o Based on observations Key points about the nature of science o Science originates in questions about the natural world o Science uses observations and evidence to construct explanations about phenomena and testable hypothesis The more observations and other kinds of evidence that support an hypothesis the stronger that hypothesis is Scientists o Employ a variety of techniques to investigate the natural world o Make their explanations public through presentations and publications o Critique the explanations proposed by other scientists In discussion section of publications Reviewing manuscripts and grant proposals Our typical experience o Body temperature of 37 degrees Celsius Range of conditions for life o Cell body temperatures from 2 C to 132 C Conditions at the average depth of the ocean Range of pressures o 1 atm to 1100 atm o 2 C to 4 C o 360 atm of pressure o No sunlight Antarctic fishes ectotherm Penguins o Keep warm at similar temperatures Endotherm Diving seals o Hold their breath for as long as 90 minutes o Dive down to 1500 m Deep sea fishes o Down to 8000 m Piezophiles o Live and have body temperatures at 2 C below the freezing temperature of most vertebrates body fluids High pressure cold temperature low food availability o Bacteria piezophiles barophiles o Pressure loving o Thrive at pressures that kill surface bacteria Thermophiles o Bacteria o Thermophiles exist at temperatures up to 132 C grow at 122 C Sharks Halophiles Tuna C o Live with molar urea in their tissues o Halophilic bacteria live in osmotic equilibrium with 3 molar salt o Live in equilibrium o Raise the temperature of their muscles above ambient as much as 15 o Are endotherms in contrast to ectothermic fish o Other endotherms Great White Shark Swordfish Midwater fish and invertebrates o Organisms living in the water column Chemistry Background Elements o Pure substances that can t be broken down into 2 or more simpler o Smallest unit into which an element can be divided substances o 92 naturally occurring elements o 118 known elements Atom Components of an atom o Nucleus Proton Neutron 1 charge 1 Dalton mass 0 charge 1 Dalton mass o Electron 1 charge Essentially without mass Atomic number Atomic mass o Number of protons in the nucleus o Number mass of protons and neutrons in the nucleus o Number of electrons number of protons o In an ion the number of electrons is not equal to the number of o Substance which can be broken down into 2 or more elements o Examples Electrical charge protons Compound NaCl Chemical bonds o The force that holds atoms together o Characterized bonds as strong or weak depending on the energy required to make or break the bond Strong Weak Covalent bonds involve sharing of electrons Non covalent bonds o Ionic interactions Attractions of opposite charges One atom donates an electron to another o Hydrogen bond between partially charged atoms What determines the number and type of chemical bonds o Number valence o Type electronegativity Electronegativity o A measure of the tendency of an atom to attract a bonding pair of o Measure of the attraction an atom has for electrons Valence vs valence electrons o Valence is the number of electrons needed to fill the outermost shell o Valence electrons are the electrons contained in the outermost shell of electrons of an atom an atom Moles and molar concentrations o 1 mole the mass of a substance equal to its gram molecular weight o 1 molar solution a solution containing 1 mole of a substance per 1 liter of solution Ionic bonds o Weak bond o Transfer of electron from one atom to another Covalent bonds o Strong bonds o Sharing of electrons to complete that valence shell Polar bonds o Unequal sharing of electrons o Partial positive and partial negative regions o No net charge Hydrogen bonds o Weak non covalent bonds o Between partial positive and partial negative charges Water Water o 70 to 90 of weight of most life forms o Sets the lower temperature limit for life o Sets the upper temperature limit Probably not o Important role in structures and properties of biological molecules o Water is a biological molecule The unusual properties of water o Result from hydrogen bonding o Water behaves as a much larger molecule than it actually is Bonds o Covalent H O 110 kcal per mole Angle 104 5 degrees Weak hydrogen bonds 4 5 kcal mol H bonding effectively makes water a larger molecule In ice a water molecule interacts with exactly 4 other water molecules In liquid water on average 3 6 or fewer other molecules interact with water Unusual properties of water o High heat capacity o High heat of vaporization o High heat of fusion o Most dense at 4 C o High dielectric o Capillary action and surface tension o Ionization Heat capacity o Amount of heat to raise temperature of 1 g of water by 1 C o 1 cal per g of water Heat of vaporization o Amount of heat to vaporize 1 g of water o 540 cal per g at 100 C Heat of fusion o Amount of heat removed to freeze 1 g of water o 80 cal per g Super cooling o Cooling of liquid below its freezing point without the formation of ice crystals o A metastable state Super cooled metastable state o Below a certain temperature molecular aggregates become larger o Embryo crystal seeds the solution when a critical radius is reached Pure water Ice forms spontaneously o In the absence of heterogeneous nucleators can super cool to 40 C o At 40 C homogenous nucleation occurs Ice nucleators o Protein o Polysaccharides o Prevent super cooling and rapid freezing Cause freezing at a higher temperature Heat of fusion o Amount of heat removed to freeze 1 g of water o 79 70 cal per g Water most dense at 4 C o Because of the hydrogen bonding structure ice lighter than water o Lakes do not freeze from the bottom up o Water can move great distances due to hydrogen bonding High dielectric o Good solvent Capillary action and surface tension Ionization o Dissociation into acid hydronium ion o And base hydroxyl ion Acids Bases and Salts o Acids produce H ions o Bases produce hydroxide ions o Salts produce neither pH scale o Log base 10 o The difference between pH 3 and pH 4 is a 10 fold difference in the concentration of H o The lower the number the higher the concentration o pH of 7 is neutral o pH below 7 is acidic o pH above 7 is basic pOH o pH pOH 14 o pH pOH Buffers
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