Unit 1: Principles of Chemistry (OLD)

• Diffusion of coloured solutions occur due to random motion of particles causing colour to spread evenly.
• Dilution works by causing solute to be further spread apart.
• Diffusion experiment of ammonia and hydrogen gas: ring forms closer to hydrogen gas' side of the tube as ammonia is faster due to being lighter.
• In the diffusion experiment of ammonia and hydrogen gas, ring takes time to form because motion is random so they collide with other air particles/not always with each other
• Saturated solutions are?

  Solutions that contain the maximum amount of solute dissolved at a specific temperature in a specific volume of solvent with left over undissolved solute in solution.
• Solubility curve example

  
• Elements are in the purest state and one type of atom only.
• Compounds are 2+ elements chemically bonded in fixed proportions wheras mixtures are 2+ elements physically "bonded" not in fixed proportions
• Pure has a fixed melting point wheras mixtures have varying melting points
• Paper chromotography can be used to seperate different dyes/inks in a mixture
• In chromotography: different dyes/inks in a mixture have different Rf values and therefore will travel different distances on the paper.
• The principle of simple distillation is to boil the solution and pass it through a condenser / condensing jacket to form pure solvent in seperate beaker on other side of condenser.
• The principle of fractional distillation is to do the same as simple distillation but with a thermometer to carefully measure and ensure a specific temperature is kept and with a fractionating column filled with glass beads that increase the likelihood of other substances in solution that have similar yet higher boiling points are more likely to cool down before reaching the condenser.
• Fractionating column works by increasing the distance traveled and surface area using glass beads.
• Filtration is used to seperate insolluble solids from liquid using a funnel and filter paper the insolluble solid cannot fit/pass through.
• Crystallation is used to obtain salt that contains water of crystillation from salt solutions by heating in an evaporating dish until crystals form on the stirring rod, (meaning the solution formed is saturized), leaving it to cool and crystallize, filtering it out and leaving it to dry by pat drying using a tissue and leaving it in a warm place.
• An atom is the smallest amount of an element
• A molecule is a fixed number of atoms bonded covalently
• Isotopes are caused by variation of neutrons in atom leading to different atomic mass with the same atomic number.
• Ar = average mass of all isotopes, measured by multiplying isotope with it's likelihood of occurence and adding all those values together
• The groups of the periodic table that are important are as follows: alkali metals, transition metals, other metals, non metals, hallides, noble gases
• Groups contain the same number of electons in outer shell (ie. hallides, alkali metals)
• Periods contain the same number of outer shells
• Protons and neutrons both way 1 amu, electrons weigh 0
• Protons have a positive charge, electrons have a negative charge
• Protons and neutrons are found in the nucleus
• Electrons are found in the shell
• Moles (mol) are used for quantifying amoutn and are relative to the number of atoms in 12g of carbon-12
• 1 mole of any substance contains 6 x 10 ^ 23 particles of said substance (avagrados number)
• Moles measure particles instead of atoms as certain elements dont exist on their own and instead as diatomic
• The steps for getting formulae from simiple compound calculations are:

  1. mass
  2. mass / molar mass
  3. divide other results of 2 by smallest result of 2 to get ratio
• Overheating salt leads to decomposition which causes too large of a mass change for accurate results
• Simple compound experiment can be used to figure out the empirical formula for hydrated salt formations (ie. CuSO4.XH2O)
• Possible mistakes made in the MgO reaction involving a crucible include:

  
  

  1. Opening the lid too often -> too much MgO smoke escapes
  2. Impure crucible/MgO -> reactions occuring with other things
  3. Overheating -> crubile reacts
• Empirical formula represents the lowest whole number ratio
• Molecullar formula shows the number of each atom
• Organic molecules typically have different molecullar formulas than their empirical formula, however ionic ones never do
• Converting from empirical to molecular formula:

  
  

  1. divide molecular/relative formula mass by relative empirical formula mass
  2. multiply empirical formula by result
• Concentration = amount of solute in solvent
• 1dm^3 = 1000cm^3