Principles of Chemistry

• Solid

  Here:

  • Regular Arrangement
  • close together
  • particles vibrate about in fixed position
• Liquid:

  Here:

  • random, arrangement
  • close together
  • move around each other
• Gas:

  Here:

  • random motion
  • particles are far apart
  • move at high speeds in all directions
• Atom:

  The smallest piece of an element that can still be recognized as the element
• Molecule:

  2 or more atoms covalently bonded together, they contain a certain fixed number of atoms
• Elements:

  Contains only one atom they can't be split into anything simpler by chemical means
• Compound

  Are formed when 2 or more elements chemically combine, elements always combine in fixed proportion
• Mixture:

  Can be made from elements and/or compounds, that are various substances mixed together and no chemical reaction occurs, with no fixed proportion
• Relative Atomic Mass Def:

  Weighted average of the masses of an element's isotopes, relative to 1/12 the mass of an atom of carbon 12, which is assigned a mass of 12
• Relative atomic mass Formula:

  Ar = (mass of isotope 1 x %isotpe 1/100) + (mass of isotope 2 x%isotope 2/100)
• Solute:

  Is the substance being dissolved
• Solvent:

  Is the liquid it's dissolving into
• Solution

  Is the mixture of a solute and solvent that does not separate out
• Saturated Solution

  Is a solution where the maximum amount of solute has been dissolved, so no more solute will dissolve in the solution
• Filtration

  Here:

  • Can be used to separate a solid from a liquid
  • The substance left is the filter is called the residue and the liquid that comes through is called the filtrate
  • Can also be used to separate 2 solids from each other if only one of them is soluble in water
• Crystallization:

  Here:

  • Separate a solute from a solution
  • Solution is heated in an evaporating basin to boil off some of the water until an almost saturated solution is formed
  • The Bunsen burner is then turned off and the crystals allowed to form as more water evaporates and the solution cools
  • The crystals can now be removed from the mixture by filtration
• Simple Distillation:

  Here:

  • can be used to separate the components of a solution
  • The water boils and is condensed back to a liquid by the condenser the salt remains in the flask
• Fractional Distillation:

  Here:

  • Used to separate a mixture of liquids such as ethanol and water (they are miscible)
  • Solution is heated to the temperature of the substance with the lowest boiling point

  The Steps:

  1. Substance will rise and evaporate first
  2. The vapor will cool and condense through the condenser
  3. Turning into a liquid that will be collected in a beaker
• Paper Chromatography:

  Here:

  • separate substances that have different solubilities in a given solvent
  • The solvent travels up the paper by capillary action, taking some of the colored substances with it; called mobile phase
  • Different substances have different solubilities so will travel at different rates, causing the substances to spread apart
• Diatomic Atoms

  Have(hydrogen)

  No(Nitrogen)

  Fear(Fluroine)

  Of(Oxygen)

  Ice(Iodine)

  Cold(Chlorine)

  Beer(Bromine)
• Empirical Formula

  Gives the simplest whole number ratio of the atoms present in a compound
• Molecular Formula:

  Shows that actual number of each type of atom present in a molecule (covalent compounds) or formula unit(ionic compound)
• Allotropes:

  Different structural forms of the same elements
• Ions:

  The transfer if electrons between atoms, forming charged particles called ions
• Cation:

  Positive ion

  Eg: Na+
• Anion:

  Negative ion

  Eg: Cl-
• Diatomic Elements:

  Pure elements that form molecules consisting of two atoms boned together
• Ionic Bonds:

  Is the strong electrostatic attraction between positive and negative ions (non-metals and metal)

  Eg: - Sodium Chlorine
• Covalent Bonds:

  Is the strong electrostatic force of attraction between the positive nuclei and the negative shared electrons in the bonded atoms(non-metals)

  Eg: - Hydrogen
• Ionic Compound Lattice Structure:

  Here:

  • compounds with ionic bonding always have giant ionic lattice structure
  • the ions are held together in a closely packed 3D lattice arrangement by the attraction between oppositely charged ions
• Describe an Ionic Lattice:

  An alternating regular structure of positive cations and negative anions held together by strong electrostatic forces of attraction
• Ionic Compound Properties:

  Here:

  • they have high melting and boiling points
  • the electrostatic attraction between oppositely charged ions is very strong
  • cannot conduct electricity when in solid form, but if you melt the compound, or dissolve them in water, they are able to conduct electricity
• Why do ionic compounds have a high MP and BP?:

  Because of the strong electrostatic forces of attraction between oppositely charged ions are strong

  This means that a lot of energy is required to break the strong electrostatic forces of attraction between oppositely charged ions in the giant lattice structure and cause the substance to melt
• How can you conduct Electricity:

  In order for electrical current to flow there must be present freely moving charged particles such as electrons or ions
• Why in Ionic Compounds solids cannot conduct electricity but liquid can?

  Here:

  • In a solid it cannot conduct electricity because the ions are in a fixed position within the lattice and are unable to move
  • In a liquid or solution it can conduct electricity because they have ions that can move and carry charge
• Simpler Molecular Structures:

  Have covalent bonds joining the atoms together, but intermolecular forces that act between neighboring molecules
• Properties of simple molecular structures:

  here:

  • have low MP and BP points but it can increase
  • weak intermolecular forces
  • cannot conduct electricity
• Why do simple molecular structure have low BP and MP?

  With the small molecules it doesn't take much energy to overcome the weak intermolecular forces
• Why can simple molecular structures MP and BP increase?

  Because as the relative molecular mass increases so will the BP and MP

  An increase in the relative molecular mass of a substance means that are more electrons in the structure, therefore there are more intermolecular forces of attraction that are needed to overcome when a substance changes state

  Larger amounts of heat energy are needed to overcome these the forces, causing the compound to have a higher MP and BP
• Why are Simple Molecular Structures Poor Conductors of Electricity?

  Because there are no free ions or electrons to carry the charge

  Most covalent compounds do not conduct at all in the solid state and this are insulators

  Eg:

  • wood