C1 revision

• Element


  Substance made from only one type of atom
• Compound


  Substance made from two or more different types of atoms chemically bonded together
• Mixture


  Two or more different elements or compounds that are not chemically bonded together
• Balancing chemical equation


  1. Can't change the little numbers

  2. Balance phosphorus by putting 2 on the right

  3. Balance oxygen by putting 3 in front of O2 on the left
• Distillation to get pure water from salt water

  1. Heat solution so water (solvent) evaporates

  2. Use condenser to turn water vapour back into liquid, leaving salt (solute) behind
• Solid


  • Particles vibrate about fixed positions, tightly packed, cannot be compressed
• Liquid


  • Particles free to move past each other, still touching, cannot be compressed
• Gas


  • Particles move with fast speeds, high kinetic energy, far apart, can be compressed
• Rutherford discovered that atoms are mostly empty space with a small, positive charge in the middle (the nucleus)
• Subatomic particles


  • Protons (positive charge, relatively large mass)
  • Neutrons (neutral charge, relatively large mass)
  • Electrons (negative charge, very small mass)
• Atomic number


  Number of protons in the atom's nucleus
• Mass number (relative atomic mass)


  Number of protons plus neutrons in the nucleus
• Electron shell filling


  1. First shell max 2 electrons

  2. Second shell max 8 electrons

  3. Etc.
• Ionic bonding


  Metals donate their outer electrons to non-metals, leaving them with a positive charge
• Covalent bonding


  Non-metals share electrons to get a full outer shell
• Reactivity groups


  • Alkali metals (group 1, very reactive)
  • Halogens (group 7, get more reactive up the group)
  • Noble gases (group 0, very unreactive)
• Metallic bonding


  Metal atoms form a lattice with a 'sea' of delocalized electrons, making them good conductors
• The formula for iron(III) oxide is Fe2O3
• Drawing structural formula and dot-and-cross diagram for methane

  1. Carbon makes 4 covalent bonds to hydrogen

  2. Structural formula shows bonds as lines, dot-and-cross shows electron pairs
• Properties of ionic compounds

  • High melting points, can only conduct electricity when molten or dissolved
• Properties of simple covalent compounds

  • Relatively low melting and boiling points, cannot conduct electricity
• Graphite can conduct electricity, diamond cannot, even though they are both giant covalent structures of carbon
• The relative formula mass of magnesium hydroxide is 58 g/mol
• 29 g of magnesium hydroxide is equivalent to 0.5 moles
• 72 g of water is needed to make 116 g of magnesium hydroxide
• Limiting reactant


  The reactant that runs out first in a reaction
• To make a 0.2 M solution of sodium chloride in 2 L of water, you need 23.4 g of sodium chloride
• Percentage yield


  Used when given actual masses of reactants and products
• Atom economy


  Uses relative atomic masses to find how much of a desired product is made compared to total reactants
• Displacement reaction


  A more reactive metal or non-metal takes the place of a less reactive one in a compound
• Oxidation


  Loss of electrons
• Reduction


  Gain of electrons
• pH


  Measure of H+ ion concentration, lower pH is more acidic, higher pH is more alkaline
• Neutralisation reaction


  1. Acid + Alkali → Salt + Water

  2. Need twice as many moles of alkali as acid to neutralise
• Electrolysis of solutions


  1. Positive ions attracted to negative cathode, reduced

  2. Negative ions attracted to positive anode, oxidised
• This is good for higher and Foundation Tier double combined Trilogy and triple separate chemistry that's topics 1 to five atoms bonding quantitative chemistry and chemical and energy changes
• If there's no number after a symbol there's an invisible one
• Balancing chemical equations


  1. Start balancing atoms that are only in compounds

  2. Balance elements that appear on both sides

  3. Use numbers in front of elements or compounds to multiply them up
• Mixture


  Any combination of any different types of elements and compounds that aren't chemically bonded together
• Solution


  A mixture of a solute dissolved in a solvent