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1 Chapter 2 Chemistry Topics:Composition of Matter Energy Solutions CPI
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2 Matter Has mass, occupies space Mass – amount of matter in an object Weight – the measure of the pull of gravity on the mass of an object Mass & weight can be used synonymously on Earth, but they are not the same thing Element – simplest form of matter that cannot be broken down by ordinary chemical means
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3 Matter, cont. Atom – simplest unit of an element retaining all the properties of that element Composed of 3 subatomic particles: Proton, neutron, electron Protons + neutrons in small, dense center (nucleus) Electrons are moving near speed of light orbiting nucleus; 3 x 10 8 m/s; electrons have more E as they move away from nucleus
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4 Atoms ParticleLocationChargeMass (amu) ProtonNucleus+1 NeutronNucleus01 ElectronOrbit-1/1872 Atomic Number = # protons Atomic Mass = # protons + # neutrons Neutral atom: # protons = # electrons Ion = charged atom caused by gain/loss of electrons
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5 Chemical Reactions Electrons – part of atom involved in chemical rxns Electrons found in energy levels in atom Level 1 – holds 2 electrons max Level 2 – holds 8 electrons max Level 3 – holds 8 electrons max When outermost energy level is full, atom is stable and unreactive
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6 Periodic Table Elements arranged on periodic table by increasing atomic # Metals on left, non-metals on right, transition metals in middle, metalloids along “stair” line Important info on table Period # - how many energy levels in atom Family # - how many valence electrons in atom (be careful of transition & rare-earth elements)
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7 Practice Name 2 metalloids. How many electrons in Ca? Name any 3 elements with 4 valence electrons. An atom has an atomic mass of 79.9 and an atomic # of 35. How many electrons does it have, what is its name? Name 2 stable atoms & tell me why they are stable. K has how many energy levels?
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8 Bonding Three types of chemical reactions are possible Ionic bonding – transfer of electrons Covalent bonding – sharing of electrons Metallic bonding – bonding of metals In biology, we are concerned with ionic & covalent bonding
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9 Ionic Bonding Occurs when a metal and a non-metal bond Metal donates electron(s); non-metal accepts electron(s) Metals have few valence electrons that are loosely held; so easily donated Non-metals have many valence electrons tightly held; so electronegativity of these atoms is strong and they accept electrons Ions formed (metal +, non-metal -) Ionically bonded compounds when dissolved in water will conduct electricity; ions dissociate forming electrolytes
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10 Covalent Bonds Occurs when non-metals bond These atoms have high electronegativity and so tend to strongly hold electrons; thus these atoms tend to share rather than donate to each other Molecule formed; no overall charge on unit
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11 Energy Ability to do work, cause change Types: Chemical – E in bonds Thermal – Heat E Electrical – E of charges Mechanical – E of motion Free Energy – E in a system available for work; E available to fuel cell rxns
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12 States of Matter States: solid, liquid, gas E increases from solid to gas Solid: definite volume & shape Liquid: definite volume & indef shape Gas: indefinite volume & shape
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13 Phase Change Diagram Phase change for Water, H 2 O Energy, KCal/Mole Temp C EP CP MP FP S L G
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14 Chemical Reactions Chemical rxns are like math equations (Yippee!) CO 2 + H 2 O H 2 CO 3 Reactants Products Double Arrow – indicates rxn proceeds both ways (reversible) Not all rxns are reversible
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15 Chemical Reactions, cont Governed by Law of Conservation of Mass & Energy Reactants = Products Chemical symbols – refer to elements Arrow ( ) is the = sign Subscripts – tell how many of each element; H 2 O Coefficients – tell how many molecules; 3CO 2
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16 Reactions in Cells Homeostasis must be maintained But rxn must proceed and E is required to begin rxn E required is Activation Energy A rxn having a net release of free energy is exergonic (exothermic) A rxn having a net aborption of free energy is endergonic (endothermic)
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17 Activation Energy Graph shows the E needed to begin a rxn to form products E Req E Rel Reaction Products Reactants AE AE = Activation E
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18 Activation Energy Problem – biological system not compatible with high energy required to begin and sustain a reaction Solution – add a CATALYST A chemical that speeds up a rxn, is not used up in the rxn, can be used repeatedly, works by lowering the activation energy Biological catalysts are ENZYMES Proteins that speed reactions by lowering AE, can be used repeatedly
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19 Another Look at AE New Lower AE Products Reactants E Req E Rel Reaction
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20 Redox Rxns Short-hand term for “oxidation & reduction” reactions Rxns where electrons are transferred between atoms Always occur together Oxidation rxn – reactant loses e - taking a + charge Reduction rxn – reactant gains e - taking a - charge
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21 Solutions Homogeneous mixture Solute – substance being dissolved Solvent – substance doing dissolving Often it is a solid in a liquid; any phase of matter may be dissolved in any phase, examples? Concentration – measure of how much solute dissolved in a solvent Ways to measure concentration % solution Molarity
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22 Solutions Saturated solution – a solution in which as much solute as possible is dissolved; temperature dependent Unsaturated solution – a solution having less than the total possible amount of solute dissolved Aqueous solution – a solution in which water is the solvent
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23 Water Universal solvent (dissolves a wide range of solutes) - Polar molecule O H H + Oxygen side slightly negative; hydrogen side is slightly positive H 2 O molecules will align to maximize +/- interactions and minimize -/- & +/+ interactions
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24 pH H 2 O will spontaneously dissociate into H+ and OH- ions; ions associate back into water molecules; equilibrium is reached; pH = 7 In solution, excess H+ ions makes it acidic In solution, excess OH- ions makes it basic
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25 pH Acids – sour, corrosive Bases – bitter, corrosive Scale: 0 to 14; 7 is neutral Log scale pH 7 = 7.0 x 10 -7 H+ in solution 1 unit of change = a 10x change in amount of ions in solution pH 4 acid has 10x more H+ in solution than pH 5 solution & 100x more H+ than a solution of pH 6
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26 Neutralization Add a base to an acid – they neutralize each other Rxn yields a salt and water A buffer another term for a base and it neutralizes acids Very important to biological systems; need to maintain proper pH of any particular system
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27 Lab Reading Quiz 1. pH measures _______________. 2. Acids release ________ when in solution. 3. Bases release _________ when in solution. 4. A solution with a pH of 4 has ____ times as many hydrogen ions in solution as pH 5. 5. Acids taste _________. Bonus: Name 2 ways to test pH.
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28 pH Quiz Answers 1. conc of H + /OH - in solution; how acidic/basic a solution is 2. H + ions 3. OH - ions 4. 10 5. tart B. pH meter, litmus paper, pH paper, indicator solutions
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