BSC2010 FINAL EXAM REVIEW Chapter 2 The Basics Matter Element anything that takes up space and has mass a substance that cannot be broken down to other substances by chemical reaction 20 25 of elements are essential to life required by an organism in minute quantities Trace elements Properties of an element neutrons no charge protons positive charge electrons negative charge substance consisting of two or more elements in a fixed ratio o o Most abundant elements in the human body carbon 18 5 hydrogen 9 5 oxygen 65 nitrogen 3 3 and calcium 1 25 o o Compound Atom Atomic mas Mass number Isotopes smallest unit of matter that still retains the properties of an element atoms of an element that differ in the number of neutrons amount of protons amount of neutrons s proton mass neutron mass Radioactive isotopes decay spontaneously giving off particles and energy Uses of radioactive isotopes dating fossils tracing atoms through metabolic processes diagnosing medical disorders o o Energy o o o o Orbital Molecule Solution Solvent Solute Molecular formula Structural formula Covalent bond capacity to cause change Potential energy energy that matter has because of its location of structure Kinetic energy energy of motion An electron s state of potential energy is called its energy level or electron shell the outermost electron shell determines chemical reactions bonds that can occur valence electrons those in the outermost shell valence shell 3D space where an electron is found 90 of the time 2 or more atoms held together by covalent bonds smallest unit of a compound that retains the properties of a compound compound in a homogenous suspension dissolving medium dissolved substance gives the type of atoms in a compound and the number of each type ex H2 gives more detailed chemical formula that shows bonds between atoms shows how atoms are arranged ex H H sharing of a pair of valence electrons by two atoms the shared electrons count as part of each atom s valence shell o o o o Single bond sharing one pair of electrons Double bond sharing two pairs of valence electrons Nonpolar covalent bond atoms share electrons equally Polar covalent bond one atom is more electronegative and the atoms do not share the electrons equally unequal sharing of electrons causes a partial positive or negative charge for each atom or molecule an atom s attraction for the electrons in a covalent bond the more electronegative an atom the more strongly it pulls Electronegativity shared electrons to itself Ions electrically charged atoms Anion negatively charged ion Cation positively charged ion attraction between an anion and a cation form salts o o Ionic bond Hydrogen bond atom Van der Waals interactions causes asymmetrical distribution Diffusion Chemical reactions formation of new compounds is a chemical reaction Equilibrium o forms when a hydrogen atom covalently bonds to one electronegative atom that is also attracted another electronegative attractions between molecules that are close together as a result of hot spots of positive or negative charge that spontaneous movement of molecules molecules move down a concentration gradient collisions between molecules can lead to rearrangement of electrons between orbitals Making and breaking of bonds and when forward and reverse reactions occur at the same rate All chemical reactions are reversible products of the forward reaction become reactants for the reverse reaction Chapter 3 1 There are four critical properties of water Cohesion Adhesion 1 2 3 Cohesion hydrogen bonds hold water molecules together helps the transport of water against gravity in plants Surface tension measure of how hard it is to break the surface of a liquid Adhesion attraction between different substances for example between water and cell walls 2 Moderation of Temperature Kinetic energy energy of motion 1 Water absorbs heat from warmer air and releases stored heat to cooler air 2 Water can absorb or release a large amount of heat with only a slight change in its own temperature 3 4 Heat measure of total kinetic energy due to molecular motion 5 6 7 Temperature the intensity of heat due to the average kinetic energy of molecules Calorie the amount of heat required to raise the temp of 1 g or water by 1 degree Celsius 1kcal 1000cal 1cal 4 184J Specific heat amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1 degree Celsius Water has an extremely high specific heat Evaporation transformation of a substance from liquid to gas 8 9 Heat of vaporization heat a liquid must absorb for 1 g to be converted to gas 3 Density 1 Water reaches its greatest density at 4 degrees Celsius 2 3 4 5 6 Ice floats in water because hydrogen bonds in ice are more ordered making ice less dense Solution a liquid that is a homogenous mixture of substances Solvent dissolving agent of a solution Solute substance that is dissolved Aqueous solution solution in which water is the solvent 4 Water is a versatile solvent Forms hydrogen bonds easily 1 2 Hydrogen shell sphere of molecules that surround each ion of an ionic compound dissolved in water 3 4 5 Molecular mass sum of all masses of all atoms in a molecule 6 A hydrophilic substance is one that has an affinity for water A hydrophobic substance is one that does not have an affinity for water Avogadro s number 6 02 x 1023 Acids and Bases Acid Base pH A hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other The hydrogen atom leaves its electron behind and it transferred as a proton or hydrogen ion H The molecules with the extra proton is now a hydronium ion H3O though it is often represented as H The molecule that lost the proton is how a hydroxide ion OH o o o any substance that increases the H concentration of a solution any substance that reduces the H concentration of a solution negative logarithm of H concentration log H determines how acidic or basic a solution is o 7 basic 7 acidic 7 neutral o o Most biological fluids have a pH of 8 substances that minimize changes in concentration of H and OH in a solution when CO2 dissolves in seawater to create carbonic acid Buffers Ocean acidification Burning of fossil fuels is a main source of sulfur oxides and nitrogen oxides react with water to form strong acids Organic chemistry Carbon atoms are tetravalence meaning they can form diverse molecules by bonding to four other atoms study of compounds that contain carbon In molecule with multiple carbons
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