Chapter 9B - Analysis of consumer products

• usually have a sharply defined melting point

• lower melting point depression • broader melting temperature range • impurities disrupt molecular/lattice solid structure • weaken forces of attraction b/w particles

• evaluates purity of substances by comparing experimental melting point to known melting point

• Analyte is dried & forced into a capillary tube • Capillary tube is placed into a heating device • The melting point is determined by recording the temperature at the moment just before the solid collapses (the miniscus of the liquid appears before the solid collapses) * process is repeated & average melting point is compared w/ known values

• if melting point is lower/broader temperature range - substance is not pure or mixture of impure substances • If melting point is lower & temperature range is narrow, analyte likely to be mixture of pure compounds

• usually have a sharly defined boiling point (within 1-2°C)

• often have a higher boiling point • additional intermolecular forces present

• Liquid mixture is placed in a round bottom flask & heated • Most volatile liquid in the mixture boils first & becomes a gas • This component condenses in the condenser & is collected as a liquid/distillate • Boiling points of collected fractions verify the components of the mixture

• compare boiling point w/ known pure samples • if the temperature of the fraction is higher, the component is not pure

• used to seperate liquids in a mixture which have very different boiling points

• used to seperate liquids in a mixture which have similar boiling points • fractioning column allows this to happen & produced purer fractions