States of Matter and Mixtures

• Particles in a solid.

  Tightly packed together in a regular arrangement, vibrate in fixed positions.
• Particles in a liquid.

  Close together but able to move past eachother, vibrate and move around eachother.
• Particles in a gas.

  Well separated with no regular arrangement, vibrate and move freely at high speeds.
• What does ‘interconversion of state’ mean?

  When matter changes from one state to another due to changes in temperature or pressure.
• Physical vs chemical change.

  Physical - affects intermolecular forces between particles.

  Chemical - affects the chemical properties and particles of a substance.
• Solid to gas

  Sublimation
• What happens when a solid changes to a liquid?


  The particles absorb thermal energy which is converted to kinetic energy, as the particles vibrate more the solid expands until the structure breaks.
• What happens when a liquid turns to a gas?

  The heated particles expand and some on the surface gain sufficient energy to overcome intermolecular forces and evaporate. Boiling point occurs when all the particles in the liquid gain enough energy to evaporate.
• What is a mixture?

  Contains 2 or more elements or compounds not chemically bonded together, the chemical properties of each substance are unchanged.
• What is a pure substance?

  A single element or compounds, not mixed with any other substance.
• How can you use melting point data to distinguish between pure substances and mixtures?

  Different substances have different melting points, so if a sample has a single, sharp melting point, it is likely a pure substance. If a sample has a range of melting points, it is likely a mixture.
• When is simple distillation used?

  To separate a solvent from a solution, e.g. salt and water.
• When is fractional distillation used?

  To separate pure liquids from a mixture of liquids, they must have different boiling points.
• How does fractional distillation work?

  Oil is heated until it evaporates into the fractioning column, vapours rise up the fractioning column and condense at the different fractions, depending on the relative boiling point of each substance.
• When is filtration used?

  To separate an insoluble substance from a solution.
• How does filtration work?

  Place the filter paper in a funnel, pour the solution containing an insoluble substance through the funnel into a conical flask, the insoluble substance will collect in the flask.
• When is crystallisation used?

  To separate a soluble solid from a solution if the solid decomposes when heated.
• How does crystallisation work?

  Pour the solution into an evaporating dish and heat gently, when crystals begin to form, remove the dish from heat and leave to cool. Once cool, filter the dry crystals out of the solution and leave them to dry.
• When is chromatography used?

  To identify soluble substances in a mixture.
• How does paper chromatography work to separate a mixture?

  The mobile phase (solvent) moves through the stationary phase (paper) so anything dissolved will travel up with it. Compounds interact differently with each phase so will move different distances through the stationary phase and will separate.
• How can chromatography show the composition of a mixture?

  Different coloured substances in the mixture will separate as they have different solubilities in the solvent and will travel at different rates.
• Why should a lid be used in chromatography?

  To prevent the solvent evaporating.
• How can chromatography show if a certain substance is present in a mixture.

  Run a pure sample of this substance next to the unknown mixture, if its Rf values matches a spot from the mixture it is likely present.
• Substances with a higher solubility will do what in chromatography?

  Travel further up the paper as the will stay in the mobile phase for longer.
• How could you separate salt and sand?

  Add water to the mixture and filter the solution, then use crystallisation.
• How can liquids be separated if the have different densities?

  They will naturally separate into two layers, use a flask with a tap on the bottom and open it to collect the bottom liquid.
• What does potable mean?

  Safe to drink.
• Steps in creating potable water.

  Sedimentation - Large insoluble particles sink the the bottom.

  Filtration - Removes small insoluble particles by passing the water through layers of sand and filters.

  Chlorination - Kills bacteria and microorganisms which are too small to be removed by filtration.
• Issues with making sea water potable.

  Extremely expensive as it requires a lot of energy, wastewater is toxic due to high concentration of salt so must be disposed of carefully.
• What is deionised water?

  Water that has had metallic ions removed.