T8

A substance that contains only one compound or element

Decrease the boiling point = sample will boil over a wider range of temperatures

Increase the melting point = sample will boil over a range of temperature

Mixtures designed for a particular use

Mixing the components in precise quantities, ensuring the formulation has the correct properties

• Paints • Fuels • Cleaning products • Cosmetics • Fetilisers • Foods

• Flame tests • Precipitation test (sodium hydroxide)

• Clean nichrome wire by dipping it in dilute hydrochloric acid • Dip the nichrome wire into a sample of the metal compound being tested • Hold wire into a BLUE flame from a Bunsen • Observe and record FLAME COLOUR Produced

Remove unwanted ions that may obscure the colour of the flame

One sample MASKS the other so you don’t know which metal ions are there

Crimson

Yellow

Lilac

Brick red

Green

Flame emission spectroscopy metal ions

• The sample is put into a flame and the light given out is passed through a spectroscope. • The output is a line spectrum that can be analysed to identify the metal ions in the solution and measure their concentrations.

• Add small amount of sodium hydroxide to unknown solution • If it forms a white precipitate, add MORE sodium hydroxide until in excess

• Add excess NaOH - Both form white precipitates but if it contains aluminium, it will redissolve to form a COLOURLESS SOLUTION

White

White

White

Blue

Green