Why Study Chemistry in Biology?

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The Size of an Atom

The Atom Definition: smallest particle of an element

C. Composition Subatomic Particle ChargeMassLocation Proton+11Nucleus Neutron01Nucleus Electron1/1840 the mass of a proton Orbiting nucleus D. If Neutral Atom: protons will = electrons

II. Elements A. Definition: substance that cannot be broken down into other substances B. Biologically important elements i. Major: C H O N ii. Minor: Ca Fe Mg I Se P K Na Cl C. Symbol: usually from first letter or two of full name

Elements Con’t. Atomic Mass amu Mass Number D.Atomic Number: # of protons in nucleus

ii. Atomic mass: average mass of an atom based on the relative abundance of its isotopes i. Mass number: count of the total number of protons and neutrons in an atom's nucleus

F. Isotopes Mass Number i. Definition: forms of the same element have same # of protons but different # of neutrons ii. Radioactive isotopes: An isotope having an unstable nucleus that decomposes spontaneously

G. Location of Electrons i.First level is closest to nucleus- holds TWO electrons ii.Second level is further out- holds EIGHT electrons iii.Third level can hold up to 18 electrons

Fill the orbital closest to nucleus first 1. Valence electrons: outermost electrons, participate in BONDING

See the different levels?! i

i. Molecules definition: two or more atoms held together by COVALENT bonds H. Chemical Compounds

ii.Compound definition: a substance containing two or more elements in a fixed ratio –Ex: H 2 O, NaCl

Decoding Chemical Formulas?? C 6 H 12 O 6 So in this molecule, there are 6 carbon atoms, 12 hydrogen, and 6 oxygen Elementsubscript is the NUMBER of ATOMS

2H 2 O The number in front of H 2 O means two entire molecules of H 2 O Think of it like 2 x (H 2 0) Sooooo… how many total atoms of H are there? Of oxygen?

Atoms want to fill their outer energy levels to be In order to do this, they will meet up with other atoms and either share or exchange electrons

Atoms share electrons so that both atoms fill their outer energy level

B. Ionic Bonds: gimme that electron! Atoms transfer electrons, becoming (+) or (-) charged This attraction brings them together –Ex: Na and Cl

i.Ions > An electrically charged atom CATIONS: positively charged ions, have more PROTONS ANIONS: negatively charged ions, have more ELECTRONS

Hydrogen Has 1 electron, needs 1 to fill its orbital Carbon Has 4 electrons in outer level, needs 4 more to fill its orbital Can form ONE bond Can form FOUR bonds

LIFE DEPENDS ON THE UNIQUE PROPERITIES OF WATER V. WATER

Questions to think about Why do put salt on the roads? Why do we salt a pot of pasta water? At a higher altitude why must we cook “boil” something longer?

A.Human Composition: Cells are 70–90% water

B. Plant Composition As much as 95% plants can be made of water

C. Formula: H 2 O

D. Bonds: i. Hydrogen bonds: the slightly (+) H atoms are attracted to nearby (-) O atoms, and develop a weak bond.

Hydrogen Bonds Hydrogen Bonds- weak bonds slightly positive H is attracted to the slightly negative O of another water molecule

ii. Covalent bonds: are shared between oxygen and hydrogen in a single molecule.

E. Polarity Polar molecule: molecule in which opposite ends have opposite electric charges Why? Water is a polar molecule: because Oxygen is an electron HOG POLAR COVALENT BOND

The polar nature of water and the effects of hydrogen bonding explain most of water's unique properties. Cohesion Adhesion Solubility Temperature moderation The lower density of ice

i. Cohesion Definition: Water “sticks” to each other Surface tension 1-inch paperclip over-filled water 3oz Dixie cup

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ii. Adhesion 1. Definition: Water molecules are also attracted to certain other molecules. 2. Ex. In trees/plants water goes against gravity Called capillary action

iii. Solubility Water is the a Universal Solvent 1. Water is able to dissolve other Polar & ionic compounds when mixed by causing the ions to break away and surround them. Water dissolves Salt (Na + Cl - )

Water (Polar) will not dissolve (Nonpolar) Like dissolve Like Water won’t dissolve oils

Temperature and Water When you heat molecules move faster When you cool molecules move slower Water takes more energy to heat because energy must break hydrogen bonds Boiling Point: 100 o C 212 o F

iv. Boiling Point Does water boil faster if you add salt to it? Water Boils when it has enough energy for the molecules to leave

v. Freezing Point What would happen if our oceans did not have salt in them? Why do we put salt on our roads? Why at effect does salt have on FREEZING POINT? 0 o C or 32 o F

LOW DENSITY OF ICE Density- amount of matter in a volume In most substances the solid state is more dense than the liquid state Water is the opposite ICE IS LESS DENSE THAN WATER and will FLOAT

LOW DENSITY OF ICE WHY????? Hydrogen bonds in ice (solid) keep molecules spaced out

LOW DENSITY OF ICE Floats Ice insulates the liquid water below allowing life to persist

G.Acids and Bases i. A water molecule can react to form ions ii. An ion is when a molecule breaks down and the atoms get a charge 1. Example: H+ and OH-

iii. pH Scale 1. How? Scale of 0-14; each pH unit represents a tenfold change in the concentration of H + ions 2. Acid definition: pH Base definition: pH 8-14

4. Buffer definition: substances that cause a solution to resist changes in pH.; works by accepting H + ions when levels rise and donating H + ions when levels fall, maintaining a constant pH a. Weak acid or base