Basic Chemistry Review

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Basic Chemistry Review
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Matter

• 1. Matter refers to anything that takes up space
  and has mass
• 2. All matter (living and nonliving) is composed
  of basic elements
• a. Elements cannot be broken down to substances
  with different chemical or physical properties
• b. There are 92 naturally occurring elements
• c. Six elements (C, H, N, O, P, S) make up 98 of
  most organisms

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Elements Contain Atoms

• 1. Chemical and physical properties of atoms
  depend on the subatomic particles
• a. Different atoms contain specific numbers of
  protons, neutrons, and electrons
• b. Protons ( charge) and neutrons (neutral
  charge) are in nucleus of atoms electrons (-
  charge) move around nucleus
• 2. Isotopes atoms with the same number of
  protons but differ in number of neutrons e.g., a
  carbon atom has six protons but may have more or
  less than usual six neutrons
• a. Isotopes used to determine age of fossils and
  in medical diagnostic and treatment procedures

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Chemical Properties of Atoms

• 1. Since protons are positively charged
  electrons are negatively charged they are
  attracted to each other
• 2. Arrangement of atom's electrons is determined
  by total number of electrons and electron shell
  they occupy
• a. Energy capacity to do work
• b. Electrons with least amount of potential
  energy are located in shell closest to nucleus
  electrons having more potential energy are
  located in shells farther from nucleus

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• c. How atoms react with one another is dependent
  upon number of electrons in outer shell
• 1) Atoms with filled outer shells do not react
  with other atoms
• 2) In atom with one shell, outer shell is filled
  when it contains two electrons
• 3) For atoms with more than one shell, the outer
  shell is stable when it contains eight electrons
• 4) Atoms with unfilled outer shells react with
  other atoms so each has stable outer shell
• 5) Atoms can give up, accept, or share electrons
  in order to have a stable outer shell

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Atoms form Molecules and Compounds

• A. Molecules two or more atoms of same or
  different elements bonded together (e.g., O2)
• B. Compound molecule of two or more different
  elements bonded together (e.g., H2O)

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Types of Bonds

• 1. Covalent bond - involves sharing of
  electron(s). Electrons possess energy bonds that
  exist between atoms in molecules contain energy.
• Sharing of a pair of electrons creates a single
  bond represented by single dash, e.g. water H2O
  is made of two single bonds H-O-H. Sharing two
  pairs of electrons is represented by two dashes,
  CC
• Know the number of covalent bonds each of the
  six most important elements can form.
• Element of covalent bondsHydrogen-1,
  Oxygen-2, Nitrogen-3, Carbon-4, Phosphorous-5,
  Sulfur-2

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Types of bonds

• 2. Ionic bond - electrons are transferred from
  one atom to another, e.g. salt NaCl
• 3. Hydrogen bond - weak attractive force between
  slightly positive hydrogen atom of one molecule
  and slightly negative atom in another or the same
  molecule
• a. E.X. in a water molecule the electrons spend
  more time orbiting the oxygen than the hydrogens,
  therefore the oxygen becomes slightly negative
  and the two hydrogens become slightly positive
• b. Such polar molecules attract each other like
  magnets

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Oxidation - reduction

• 1. Oxidation   the loss of electrons (or loss of
  hydrogen atoms), a molecule that loses an
  electron is oxidized
• 2. Reduction the gain of electrons (or gain of
  hydrogen atoms), a molecule that gains an
  electron is reduced

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Water

• A. Life evolved in water
• All living things are 70-90 water
• Because water is a polar molecule, water
  molecules are hydrogen bonded to each other
• a. hydrophilic molecules - polar molecules
  attracted to water molecules
• b. hydrophobic molecules - non-polar molecules
  repelled by water

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Properties of Water

• 1. Water resists temperature changes because
  hydrogen bonds between water molecules require a
  large amount of heat to break
• a. Calorie amount of heat energy required to
  raise temperature of one gram of water 1 C. This
  is about twice that of other liquids
• b. Water has a high heat of vaporization - takes
  540 calories to change water to a gas
• c. When animals sweat, evaporation of the sweat
  takes away body heat, thus cooling the animal
• d. Because water resists temperature changes the
  earth's surface temperature is moderate and
  organisms are protected from rapid temperature
  changes, this helps them maintain normal
  temperatures

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• 2. Water is universal solvent, facilitates
  chemical reactions both outside of and within
  living systems
• a. Water is a universal solvent because it
  dissolves a great number of solutes
• b. Important because living organisms get and
  transport most of needed chemicals in water or
  water based solutions

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• 3. Water molecules are cohesive and adhesive
• Cohesion - like molecules cling to each other
• Adhesion - ability to adhere to polar surfaces
  water molecules have positive, negative poles.
• Capillarity - the tendency for a liquid to move
  upward against pull of gravity through a narrow
  space, e.g. water rises up tree from roots to
  leaves through small tubes
• 1) Adhesion of water to walls of vessels prevents
  water column from breaking apart
• 2) Cohesion allows evaporation from leaves to
  pull water column from roots

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• 4. Frozen water is less dense than liquid water 
• a. Below 4 C, hydrogen bonding becomes more
  rigid but open, causing expansion
• b. Because ice is less dense, it floats
  therefore, bodies of water freeze from the top
  down
• c. This means that ice floats and the bottoms of
  lakes and oceans are still available for life and
  also insulated during cold weather

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Acids and Bases

• 1. Water dissociates - has a tendency to
  spontaneously break into hydrogen and hydroxide
  ions
• H20 ---gt H (hydrogen) OH- (hydroxide)
• 2. Acid molecules dissociate in water, releasing
  hydrogen ions (H) ions 
• Hydrochloric acid (HCl) is a strong acid HCl
  ---gt H Cl
• 3. Bases are molecules that take up hydrogen ions
  or release hydroxide ions
• Sodium hydroxide (NaOH) is a strong base NaOH
  ---gt Na OH-

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• 4. pH scale, which ranges from 0 to 14, is used
  to indicate the strength of acids and bases
• a. pH a measure of hydrogen (H) ion
  concentration in a solution
• b. Low pH value indicates a high concentration of
  H ions (acids)
• c. High pH value indicates a low concentration of
  H ions (bases)
• d. pH value of 7 is neutral, i.e. the solution
  has an equal concentration of H and OH- ions
• e. pH scale is logarithmic, i.e. a ten fold
  difference for each number
• E.X. pH 4 is 10 times more acidic than 5, and
  100 times more acidic than 6

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• 5. Buffers keep pH steady and within normal
  limits in living organisms, e.g. blood pH is 7.4
• a. Buffers stabilize pH of a solution by taking
  up excess hydrogen or hydroxide ions
• b. Carbonic acid helps keep blood pH within
  normal limits
•  

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Salts

• Any compound that results from the chemical
  interaction of an acid and a base
• Dissociate in solution to become ions
• See common salts on page 47

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Solutions Colloids Suspensions
Homogeneous Heterogeneous Heterogeneous
Particle size  0.01 - 1 nm can be atoms, ions, molecules Particle size  1 - 1000 nm, dispersed can be aggregates or large molecules Particle size  over 1000 nm, suspended can be large particles or aggregates
Do not separate on standing Do not separate on standing Particles settle out
Cannot be separated by filtration Cannot be separated by filtration Can be separated by filtration
Do not scatter light Scatter light (Tyndall effect) May scatter light, but are not transparent

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Organic Substances

• Carbohydrates
• Provide energy that cells require
• Contribute to cell structure
• Built by simple sugar molecules (monosaccharides)

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• Lipids (Fat, Phospholipids, Steroids)
• Supply energy, build cell parts
• Basic building block of fat molecules is
  combination of glycerol and fatty acids

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• Protein
• Serve as structural materials, energy sources,
  hormones, cell surface receptors, and enzymes
• Enzymes speed chemical reactions without being
  consumed
• Amino acids are building blocks of proteins
• Proteins vary in the number and types of amino
  acids contained and in their sequence
• Amino acid chain of protein folds into a complex
  shape that is maintained by hydrogen bonds
• Excessive heat, radiation, electricity, altered
  pH, or chemicals can alter proteins

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• Nucleic Acids
• Nitrogen base, pentose sugar, phosphate)
• Genetic material and control cellular activities
• Nucleic acid molecules composed of mucleotides
• Adenine A
• Guanine G
• Cytosine C
• Uracil U
• Thymine T
• A G are purines (large 2 ring bases)
• C, U, T are pyrimidines (small single ring
  bases)

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Important Nucleic Acids

• DNA (deoxyribonucleic acid)
• Double stranded polymer (double helix)-twisted
  ladder
• Nucleotides building are A, G, C, and T
• Pentose sugar is deoxyribose
• Stores information that cell parts use to
  construct specific protein molecules Blueprint
• Nucleotides held by hydrogen bonds
• A always bonds to T
• G always bonds to C

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• RNA (ribonucleic acid)
• Help synthesize protein
• Pentose sugar is ribose
• Single strands of nucleotides
• A, G, C, U (U replaces T)
• A always bonds to U
• G always bonds to C

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Three types of RNA

• Transfer RNA (tRNA)
• Small clover leaf shaped
• Translate messages from mRNA
• Messenger RNA (mRNA)
• Long nucleotides that resemble half-DNA molecules
• Carry messages from DNA for building a
  polypeptide (amino acid chain)

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• Ribosomal RNA (rRNA)
• Forms ribosomes (site of protein synthesis)
• Nucleolar organizer