Ba 2 Si 3 C CHe 2 mistry IN: P What do you know about Chemistry by looking at this slide?

Introduction Laws of chemistry govern the structure and function of all living things !

Matter a.Everything consists of matter b.Anything with mass & volume c.Building blocks = atoms d. Properties: mass = quantity of matter volume = amount of space occupied density = mass/volume weight = pull of gravity

FORMS OF MATTER a.Element = pure substance made of only one kind of atom  Cannot be chemically broken down into other substances  Life requires about 20  About 111 (92 occur naturally)  C arbon H ydrogen O xygen N itrogen (make up 95% of living matter organisms)

b.Compound = 2 or more elements in a fixed ratio Examples: H 2 O, CO 2, NaCl - Formed by both ionic and covalent bonds c. Molecule = simplest part of a substance that retains all the properties of that substance - Formed by covalent bonds d. Both represent different combinations of atoms H 2 O – More than 1 type of atom O 2 –one type of atom Form both a molecule and a compound. Form a molecule, but not a compound

Atoms a. Determine behavior of matter b. Subatomic Particles protons (p+) neutrons (n o ) electrons (e-) c. Electrons in energy levels (Orbitals = 3-D space where e- found 90% of the time) d. Electrons are only particle involved in chemical reactions make up 99% of mass

6 < Atomic Number C < Chemical Symbol Carbon < Name < Atomic Mass PERIODIC TABLE OF ELEMENTS a.Atomic Number (unique for each element ) = # of protons in the nucleus = # of electrons in a neutral atom b. Atomic Mass = # protons and neutrons in the nucleus

Orbitals of Atoms A.Valence electrons: e- in outermost shell B. Valence shells are complete (happy ) when full C. 1 st orbital= 2 2 nd orbital= 8 3 rd orbital= 8 4 th orbital= 18

ION ( SPECIAL ATOMS) a. Atom that gains or loses electrons b. Have an unequal number of e- and p+ c. Have net negative or positive charge d. Very reactive atoms Ion

Formation of Compounds by Bonding A.Compounds = 2 or more elements in a fixed ratio B. Have new properties from atoms C.Covalent Bonds = 2 atoms share one or more valence electrons (forms molecules); very strong bond - formed by atoms on the same side of the periodic table (consider H is on the right side) D.Ionic Bonds = transfer of electrons; formed by electrical attraction between two oppositely charged ions. (forms crystals) - formed by atoms on opposite side of the periodic table (consider H is on the right side)

Review Contrast and Compare BondWhat happens to electrons? What type of compound is formed? Formed by what atoms? Ionic Covalent

Chemical Formulas 1.Molecular = each element represented by its symbol; proportions fixed; and indicated by subscript. Examples: NaCl, H 2 0, H 2, O 2 2.Structural = shows number and kind of atoms and how atoms bond together (lines represent bonds) Example: H-O-H, H-C=C-H

Chemical Reactions a. = process of breaking and/or forming chemical bonds b. Reactants go to products: 3H 2 + N 2  2NH 3 (reactants) (products) c. Equations must be balanced d. Mass cannot be created or destroyed (Law of Conservation of Mass)

Chemical Reactions Important for Life A.Photosynthesis 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 Glucose B. Cellular Respiration C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + Energy Light Energy Chlorophyll

Dissociation of Water Molecules Hydrogen atoms shared by 2 water molecules may shift from one molecule to another –Causes the H atom to leave it’s electron behind –Hydrogen ion is transferred (single proton +) –Water molecule that lost a proton is now a hydroxide ion (OH - ) –Proton binds to another water molecule, which then becomes a hydronium ion (H 3 O + ) Simplified it is referred to as: –H 2 O H + + OH - Water dissociates into hydrogen ion and hydroxide ion

Acids and Bases A.Water molecules ionize (break apart) forming ions. B.When water ionizes, it releases a number of H + and OH - ions. C.Acids release H + ions D.Bases release OH - ions E.BUFFERS = Keep pH normal in living organisms; take up excess H+or OH- ions

Acid and Base Color Charts

pH Changes pH scale is used to determine concentration of H+ ions in a solution Hydrogen and hydroxide ions are very reactive Changes in concentration greatly affect a cell’s proteins and other molecules Concentrations are equal in pure water, adding solutes (acidic or basic) can alter the balance

Characteristics Acids taste sour, are corrosive to metals, and turn litmus paper red. –become less acidic when mixed with bases.bases Bases feel slippery, taste bitter, strong bases can burn your skin, & turn litmus paper blue. –become less basic when mixed with acids.acids

PH Scale Higher concentration of Hydrogen ions H + Higher concentration of Hydroxide ions OH -

Each step is ten fold Ex: How many more H + at pH of 1 than pH of 3? 10 x = 100

Buffers Internal pH of living cells is close to 7 –Slight changes can be harmful Buffers are substances that minimize changes in the concentrations of H + and OH - in a solution –Buffers work by accepting H+ when in excess or donating H+ if depleted Buffer found in human blood (carbonic acid; H 2 CO 3 ) –Dissociates into HCO 3 - and H + (bicarbonate ion and hydrogen ions)

Acids and Bases ACIDBASE Definition Ion Symbol Examples Characteristics pH Range Color that the litmus paper turns