C1

• There are 118 elements
• Chemical reactions must have:

  • compounds are broken up/formed
  • at least one new substance created
  • measurable energy change
  • no atoms are created or destroyed
• Filtration:

  separates mixtures that contain soluble and insoluble components (solids and liquids)

  pours mixture through filter paper

  insoluble solid is trapped by filter paper

  liquid runs through filter paper and is collected below
• Crystallization:

  separates solutions into solvents (liquid) and solutes (solid)

  heats the mixture so that the solvent evaporates

  crystals of the solutes (dissolved solids) will form

  collect the solvent (liquid) by condensing it as it evaporates
• REQUIRED PRACTICAL Chromatography:

  separates solutions with a number of different solutes (solids) in the solvent

  solvent (liquid) travels up the paper and carries the solutes with it

  different solutes move at different speeds, so they separate on the paper
• Rf value = distance moved by solute ÷ distance moved by solvent
• Simple Distillation:

  separates two liquids with different boiling points

  the mixture is heated until the liquid with the lower boiling point starts to boil

  the vapor released passes through a condenser, where the gas cools back into a liquid

  simple distillation can also separate a solute from a solvent if the solvent has a lower boiling point than the solute
• Fractional Distillation:

  separates many liquids with different boiling points

  the mixture is slowly heated until the liquid with the lowest boiling point boils and then condenses

  increase the temperature slowly to collect other fractions
• History of the atom:

  • in 1897 J. J. Thompson discovered electrons
  • modelled the atom as a 'plum pudding' - a ball of positive charge (dough), with negative electrons embedded in it (raisins); only electrons had been discovered, not protons
• History of the atom:

  • in 1909, Ernest Rutherford found that alpha particles could bounce back off atoms’ nuclei
  • Rutherford concluded that an atom's mass is concentrated in the atom's positively charged nucleus and its protons
• History of the atom: Niels Bohr discovered that electrons orbit the nucleus in energy shells
• History of the atom: in 1932, James Chadwick discovered that some particles in the nucleus have no charge at all: neutrons
• Isotopes: atoms of the same element always have the same number of protons, but can have a different number of neutrons

  • average relative atomic mass = (% of isotope 1 x its mass) + (% of isotope 2 x mass) ÷ 100
• Ions: atoms of the same element can have the same number of protons, but a different number of electrons
• Metals are found on the left side of the table, as they have few electrons on their outer shell, and when they react, they lose 1 or more electrons to form positively charged ions
• Non-metals are found on the right side of the table, as they have many electrons in their outer shell, and when they react, they either gain electrons to form negatively charged ions or share electrons to form neutral molecules