1 Chapter 2 Chemistry Topics:Composition of Matter Energy Solutions CPI

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

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

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

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

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)

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?

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

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

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

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

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

13 Phase Change Diagram Phase change for Water, H 2 O Energy, KCal/Mole  Temp  C  EP  CP  MP  FP  S L G

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

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

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)

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  

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

19 Another Look at AE  New Lower AE Products Reactants E Req E Rel Reaction 

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

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

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

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

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

25 pH Acids – sour, corrosive Bases – bitter, corrosive Scale:  0 to 14; 7 is neutral  Log scale  pH 7 = 7.0 x 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

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

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 Acids taste _________. Bonus: Name 2 ways to test pH.

28 pH Quiz Answers 1. conc of H + /OH - in solution; how acidic/basic a solution is 2. H + ions 3. OH - ions tart B. pH meter, litmus paper, pH paper, indicator solutions