Chemistry

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Chemistry

• Chapter 2

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Chemical Elements

• Matter anything that has mass and takes up
  space
• 3 phases solid, liquid, gas
• Elements basic substance which compose all
  matter cannot be broken down into other
  substance by ordinary chemical means
• 92 naturally occurring elements

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Important elements in biology

• 6 elements make up 98 body weight of organisms
• Carbon found in all organic molecules
• Hydrogen found in all organic molecules and
  water
• Nitrogen important component of amino acids and
  nucleic acids
• Oxygen necessary for aerobic respiration,
  oxidation reactions, and water
• Phosphorus important constituent of ATP and DNA
• Sulfur found in some amino acids

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Chemical Elements
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Atoms

• Atomic Theory elements consist of particles
  called atoms
• Atoms smallest unit of matter
• Subatomic particles
• Protons positively charged particles found in
  the nucleus
• Neutrons neutral particles found in nucleus
• Electrons negatively charged particles which
  orbit the nucleus

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Electrons

• Electrons found in orbitals around the nucleus
  of the atom balance positively charged protons
  in nucleus
• Bohr models
• First orbital can have 2 electrons
• Second and third orbitals can have 8 electrons
  (octet rule)

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Bohr Models of Atoms
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Periodic Table

• Atomic symbol one/two letter representation for
  each element
• Mass number sum of protons and neutrons
• Atomic number number of protons

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Periodic Table

• Elements grouped in periodic table based on
  individual characteristics
• Vertical columns are groups
• Horizontal rows are periods

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Periodic Table
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Isotopes

• Isotopes atoms of the same element with a
  differing number of neutrons
• Radioactive isotopes spontaneously decay and give
  off energy in the form of rays and subatomic
  particles
• Becquerel discovered uranium

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Isotopes

• Important in Biology and Medicine
• Can be used as tracers
• C14 Melvin Calvin
• I131 Medicine
• Glucose - Medicine

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Compounds and Molecules

• Compound - two or more different types of atoms
  bonded together
• Molecule - two or more atoms bonded together the
  smallest part of a compound that still retains
  the properties of the compound

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Bonds

• Bonds contain energy
• Types of bonds
• Ionic bonds
• Covalent bonds
• Hydrogen bonds

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Ionic Bonds

• Ionic bonds formed when electrons are
  transferred from one atom to another
• Electron transfer causes a charge imbalance in
  each atom
• Ions
• Sodium Chloride

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Sodium Chloride
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Covalent Bonds

• Covalent bonds formed when two atoms share
  electrons so that each atom has a complete outer
  shell
• Molecule Shapes
• Molecules have three-dimensional shapes
• Models
• Ball and stick
• Space-filling

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Covalently Bonded Molecules
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Covalent Bonds

• Nonpolar covalent bonds formed when sharing of
  electrons between atoms is equal
• Electronegativity is the attraction of an atom
  for the electrons in a covalent bond
• Polar covalent bonds formed due to unequal
  sharing of electrons between atoms
• Water

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Hydrogen Bonds

• Hydrogen bond formed when polarity within a
  water molecule causes the hydrogen atoms in one
  molecule to be attracted to the oxygen atoms in
  the other water molecules
• Weak and easily broken
• Many together can be quite strong

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Water Molecule
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Properties of Water

• High heat capacity
• Great deal of energy necessary to heat or cool
  water
• H bonds absorb heat without large increase in
  temperature
• Water holds onto heat
• Important for maintaining internal temperature in
  organisms

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Heat Content of Water
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Properties of Water

• High heat of vaporization
• Large number of hydrogen bonds must be broken to
  evaporate water

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Properties of Water

• Solvent water is an excellent solvent due to
  polarity
• Solution contains dissolved substances, solutes
• Ionic bonds
• Polar molecules

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Properties of Water

• Cohesive water molecules are attracted to other
  water molecules
• contributes to high surface tension
• Adhesive water molecules are attracted to other
  charged substances

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Water as Transport Medium

• Cohesion and adhesion

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Properties of Water

• High surface tension due to strong force
  between water molecules

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Properties of Water

• Density frozen water less dense than liquid
  water

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Density

• How density effects ecosystem

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Acids and Bases

• Acids substance that donates hydrogen ions (H)
  to a chemical reaction
• HCl
• Acetic acid
• H2SO4

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Acids and Bases

• Bases substance that donates hydroxide ions
  (OH-) to a chemical reaction
• NaOH
• NH3OH

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Acids and Bases

• pH scale used to indicate acidity and basicity of
  a solution
• Ranges from 0-14
• 7 Neutral
• gt7 Base
• lt7 Acid

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pH of common items
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Acids and Bases

• Buffer reversible chemical reactions designed
  to maintain pH levels
• H2CO3 ? H HCO3-

dissociates
re-forms
Carbonic acid
Bicarbonate ion
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Chemical reactions
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Chemical Reaction

• Chemical Reaction process leading to changes in
  matter
• Chemical equation attempt to demonstrate in a
  shorthand form what is taking place in a chemical
  reaction
• H2O2 ? H2O ½O2

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Chemical Reaction

• Reactants indicated on the left side of the
  equation
• Products indicated on the right side of the
  equation
• H2O ½O2 ? H2O2
• Reactants Products

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Enzyme

• Enzyme molecule that speeds a reaction by
  bringing reactants together and the enzyme may
  even participate in causing the reaction to occur
• Catalase
• H2O2 ? H2O ½O2

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