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Edexcel iGCSE Chemistry Notes | Topic 1

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  • The three states of matter are
    • solid: close together in neat rows, vibrate, low energy
    • liquid: close together, move around slowly, some energy
    • gas: far apart, move around in random directions, high energy
  • Changes of state: melting, evaporating, condensing, freezing, sublimation.
  • For a change of state, particles need to move fast or slow enough to break or build the forces of attraction.
  • Diffusion: spreading of particles in a gas or liquid with a net movement of particles from areas of high concentration to low concentration until uniform.
  • Solute: the substance that dissolves.
  • Solvent: the liquid in which it dissolves.
  • Solution: the liquid formed.
  • Saturated solution: is a solution into which no more solute can be dissolved.
  • Solubility: maximum mass of a solute that dissolves in 100g of solvent.
  • Practical: investigate the solubility of a solid in water at a specific temperature
  • Element: The simplest type of substances made up of only one type of atom.
  • Compound: Two or more elements chemically combined.
  • Mixture: Two or more elements not chemically combined.
  • Pure substances: have a fixed melting and boiling point, but that a mixture may melt or boil over a range of temperatures e.g. water 1000C.
  • Simple distillation:
  • Fractional distillation:
  • Filtration:
  • Crystallisation:
  • Paper chromatography:
  • Atom: An atom is the smallest part of an element.
  • Molecule: A molecule is made of a fixed number of atoms covalently bonded together.
  • Relative Charge: Proton (+1), Neutron (0), Electron (-1)
  • Relative Mass: Proton (1), Neutron (1), Electron (0)
  • Protons and neutrons are in the nucleus. Electrons are in the shells.
  • On each element in the periodic table, the big number is the mass number and the smaller number is the proton number.
  • Mass number: number of protons and neutrons.
  • Proton number: number of protons.
  • Isotope: atoms with the same number of protons but different number of neutrons.
  • Relative atomic mass (Ar) = (mass x %) + (mass x %) + .../ 100%
  • The periodic table is arranged in order of atomic number, in groups.
  • Group number: the number of electrons in the outer shell, so elements in the same group have similar chemical properties
  • e.g. Group 0 (or 8) elements are very unreative. They are called noble gases.
  • 1st shell: up to 2 electrons, 2nd and 3rd Shell: up to 8 electrons.
  • Metals: conduct electricity
  • Non-metals: do not conduct electricity, have oxides, & they react with acids.
  • Metals: left. Transition Metals: middle. Non-metals: right.
  • Moles = Mass/ Mr.
  • Atom economy = (Mr of desired products/ Mr of all products) x 100
  • Percantage yield = (Actual Moles/ Expected Moles) x 100