Experimental chemistry

• The SI unit of time is second
• The SI unit for temperature is kelvin (K) and is represented by the symbol K.
• The SI unit for length is the metre (m)
• The SI unit for mass is kilogram (kg)
• The SI unit for volume is the cubic meter (m3)
• A pipette is used for measuring accurate fixed volumes of liquids.

  ( 10cm3 or 25cm3 )
• Volumetric flask is used to measure larger fixed volumes
• Measuring cylinders are used to measure a range of volumes to the nearest 0.5 cm3
• Burette is used to measure to the nearest 0.05 cm3
• A magnet can be used to separate magnetic solids from non-magnetic solids.
• A sieve can be used to separate solids with different particles sizes
• A suitable solvent can be used to separate solid-solid mixtures in which only one of the solids is soluble in the solvent
• Sublimation can be used to separate a substance that changes from solid to gaseous state directly
• Filtration can be used to separate insoluble solids from liquids
• Evaporation to dryness is used to separate a dissolved solid from its solvent by heating the mixture until all the solvent has vaporised. Only works when the solid does not decompose under heating.
• Crystallisation is used to obtain a pure solid from its saturated solution . A saturated solution is one which no more solute can be dissolved. Used when solid decomposes under heating
• Simple distillation is used to separate a pure liquid solvent from a solution.
• A separating funnel is used to separate immiscible liquids
• Chromatography is used to separate a mixture of substances which have different solubilities in a given solvent
• Chromatograms show the separated substances on the paper after chromatography
• The Rf value = distance travelled by the substance

  /

  distance travelled by the solvent
• The solvent front is the final distance travelled by the solvent
• The start line is where the original position of the dyes is
• A way to identify colourless substances on a chromatogram is by using a locating agent.
• Fractional distillation is used to separate two miscible liquids with different boiling points.
• A pure substance has a specific melting and/or boiling point under fixed conditions