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Chemistry
Why learn about chemistry in biology?All living things share the same
chemical building blocks.
All living things depend on chemical processes for survival.
Matter: ◦Anything that takes up space and
has mass.
◦Example: rocks, wood, air, metal, paper, etc.
Element:◦A pure substance that cannot be
broken down into other substances.
◦Example: gold, helium, mercury, oxygen
Elements continued…25 essential elements (elements you can’t
live without)
4 elements make up 96% of living matter- oxygen, hydrogen, carbon, and nitrogen.
The other 4% is made up of mostly calcium, phosphorus, potassium, and sulfur.
Trace elements: make up less than .01% of your body mass, but are essential to your health.◦Examples: iodine, iron, magnesium, copper,
fluorine
Compound:◦A substance containing 2 or more
elements that are chemically combined.
◦Examples: Water H2O
Oxygen O2
Carbon Dioxide CO2
AtomsAtom: smallest particle of an
element
◦Made of subatomic particles Proton: single unit of positive charge Electron: single unit of negative charge Neutron: has no electric charge (neutral)
◦Nucleus: central core of an atom, made of protons and neutrons. Therefore, the nucleus has a positive charge.
Atomic number: number of protons
◦All atoms of the same element have the same number of protons, and therefore the same atomic number.
◦No two elements have the same atomic number.
Periodic Table
Label the families in your periodic table:◦Metals/ Nonmetals◦Noble Gases◦Halogens◦Alkali metals◦Alkaline Earth metals
Fill in the table.
Isotopes◦same # protons, different #
neutrons.
Radioactive isotope: nucleus decays over time, giving off radiation and energy.
Example: Carbon-14
** Carbon-12 and Carbon-13 are very stable and will not change over time.
Energy Levels/Orbitals◦Electrons differ in the amount of
energy they have
◦Electrons differ in how tightly they are held by the t protons in the nucleus.
◦Electrons fill the lowest energy level (closest to the nucleus) FIRST, then move to the higher energy levels, which are farther away from the nucleus.
Energy Levels/Orbitals◦First “energy level” or “oribtal” is
closest to the nucleus. Can hold up to 2 electrons Example: Hydrogen
◦Second energy Holds up to 8 electrons Example: Oxygen
Energy Levels/Orbitals
A partially filled energy level makes an atom chemically reactive.
◦ This means they react with other atoms because they WANT to fill their outer energy level.
Chemical BondingAn attraction between 2 atoms
that are transferring, receiving, OR sharing electrons.
◦Ionic Bonds: transferring electrons Example: NaCl
◦Ions: atoms that become electrically charged (either positive or negative)**This happens by either losing or
gaining an electron.
Chemical BondingCovalent Bond: sharing electrons
◦Examples: H2O
CH4
The number of bonds an atom can form usually equals the number of “extra” electrons in the outermost/ highest energy level.
Molecule: 2 or more atoms that are covalently bonded together form a molecule.
Modeling Molecules:◦Chemical formula◦Structural formula◦Space model
Try drawing these..C and H
C and O
H and O
Chemical ReactionsAtoms are not created or
erased in chemical reactions, they are just rearranged.
Molecules are constantly being rearranged. Bonds are broken and new bonds are formed.
When a bond is broken, energy is absorbed from the surroundings.
When a bond is built, energy is released from the surroundings.
Chemical ReactionsChemical Equation
◦Reactants: starting materials◦Products: ending materials
WaterPolarityHydrogen BondingAdhesion and CohesionVery StableSpecial Density Universal Solvent
ElectronegativityOxygen is the most
electronegative element.
It pulls electrons closer to it’s orbital and therefore gives the atom a slightly negative charge and makes other atom slightly positive
PolarityPolar molecule: a molecule in which
there is an internal separation of electric (electronegativity) charge.◦Example: Water
**Water is NOT the only polar molecule!!
(–) (–)
O
HH
(+) (+)
Hydrogen bonding
Hydrogen Bond: water molecules are held together by hydrogen bonds, due to the polarity of the molecule.
This is a very weak bond because electrons are not being shared or transferred. (velcro)
Adhesion and CohesionCohesion: the tendency
of molecules of the same kind to stick to each other.◦Ex: water sticks to water
Adhesion: the tendency for molecules to be attracted to unlike molecules.◦Ex: water sticks to a glass
Water is very StableMust gain or lose a lot of energy
in order for the temperature to change!
**This is why coastal areas have less extreme temperatures than inland areas.
Density: the amount of matter in a given volume.
High density: tightly packedLow density: loosely packerIn most substances, the solid
state is more dense.In water, the solid state (ice) is
less dense.◦Ice floats!
Think: Why is this important for life?
DissolvingSolution: a uniform mixture of
two or more substances
Solvent: the substance that dissolves the other substance
Solute: the substance being dissolved
Aqueous solution: when water is the solvent
Acids and BasesIn an aqueous solution,
some molecules of water break apart into H+ ions and OH- ions.
Other chemical compounds can contribute additional H+ ions as well.
Acids and BasesAcid: a compound that
donates H+ ions to solutions.◦HCl (hydrochloric acid)
breaks apart completely in an aqueous solution forming H+ ions and Cl- ions.
◦0-6.9 on pH scale
Acids and BasesBase: a compound
that removes H+ ions from a solution.◦NaOH (sodium
hydroxide)does this by adding OH- to an aqueous solution, which bond with H+ ions in the solution, forming extra water molecules.
◦7.1-14
Acids and BasespH scale:
describes how acidic or basic a solution is.
The pH scale ranges from 0 (most acidic) to 14 (most basic).
Acids and BasesEach pH unit represents
a change in the concentration of H+ ions tenfold.◦Ex: lemon juice at pH 2 has
10x more H+ ions than the same amount of grapefruit juice at pH 3.
Pure water and aqueous solutions that have equal amounts of H+ and OH- ions are said to be neutral, with a pH of 7.
Acids and BasesBuffers:
substances that cause fluids to resist changes in pH.
◦Accepts H+ ions when the levels are too high.
◦Donates H+ ions when the levels are too low.
Acidic solution Neutral solution Basic solution
Acidic solution
pH scale
Battery acid
1
2
3
4
5
Lemon juice, gastric juice
Grapefruit juice, soft drink,vinegar, beer
Tomato juice
Neutral solution
Basic solution
NEUTRAL[H+]=OH–]
Incre
asin
gly
AC
IDIC
(Hig
her
con
cen
trati
on
of
H+)
Incre
asin
gly
BA
SIC
(Low
er
con
cen
trati
on
of
H+)
Rain water
Human urine
Saliva
Pure water
6
7
Human blood,tears
Seawater
8
9
10
11
12
13
Milk of magnesia
Household ammonia
Household bleach
Oven cleaner
14
Functional GroupsSmall characteristic groups of
atoms that are frequently bonded to the carbon skeleton of organic groups.
They have specific chemical and physical properties.
They are usually chemically reactive.
Depending on their number and arrangement, they determine unique chemical properties or organic molecules in which they occur.
Functional GroupsHydroxyl GroupCarbonyl GroupCarboxyl GroupAmino GroupPhosphate GroupMethyl Group
Hydroxyl Group--OH
It is polar because Oxygen draws the extra electrons from the rest of the molecule, making it slightly negative on that side.
Makes the molecule it is attached to soluble
Found in alcohols
Carbonyl Group--CO
Also polar
Makes the molecule water soluble
Found in sugars
Ex: aldehyde and ketone
Carboxyl Group --COOH (hydroxyl and carbonyl
group)
Also polar
Makes the molecule water soluble
Present in some amino acids (carboxyl acids)
It is SO polar, that is dissociates as H+ (acid) sometimes.
Amino Group--NH2
Also polar
Makes the molecule water soluble
Present in all amino acids
Acts as a weak base because it can accept H+ ions
Phosphate GroupH3PO4
Polar
Makes the molecule water soluble
Used for energy storage
Loss of 2 protons by dissociation will leave the molecule reactive
Since is can lose protons, it has acidic properties
MethylCH3
Nonpolar
Hydrophobic
****Properties come 2nd to all other functional groups!