CC2 Separating Substances

• A mixture contains different elements and/or compounds that are not chemically joined together.
• Pure substances – contain one substance only
• Impure mixtures – contain more than one substance
• Pure substances have sharp melting and boiling points
• Impure mixtures have melting and boiling points that spread over a range of temperatures
• filtration - This process is used to separate an insoluble solid from a liquid.
• crystallisation - This process is used to separate a solute from the liquid it is dissolved in solvent. Only the solute is collected as crystals as the solvent evaporates away.
• Eventually a point is reached when no more solute can dissolve in a solvent. It is said to be SATURATED.
• distillation = This process is also used to separate a solute from the solvent.

  But it separates them and then collects them both. The solvent evaporates then condenses. The solute is left behind.
• Fractional distillation is used to separate mixtures of liquids from each other. 

  It uses the fact that each liquid has a different boiling point
• • chromatography can be used to separate and identify components in soluble mixtures
• rf value = distance by substance / distance by solvent
• potable water from fresh water = sedimentation, filteration, chlorination
• potable water from sea water = desalination, distillation
• Laboratories always use distilled water which is 100% pure.
• Tap water is very safe to drink but is still not 100% pure as it contains dissolved chemicals.
• • A hazard is the source of possible damage to a person or their health.
• A risk is the chance of a hazard causing harm.