Chemistry Tuition Singapore Secondary Science Tuition – Separating Mixtures Solid – Solid

SEPARATING MIXTURES

• There are physical methods which can be used to separate a mixture to obtain pure substances again.
• The choice for selecting a suitable physical method is determined by the nature of the mixture.

Solid-solid

Two different solid substances mixed together such as sand with salt or iron powder with sulfur

Solid-liquid

Salt solution, sugar solution

Liquid-liquid

Alcoholic solution, crude oil

Quantity of components

Sample containing minute amount of components such as food dyes, food colouring and inks

SEPARATING SOLID-SOLID MIXTURES

Magnetic attraction

This technique uses magnets to separate magnetic substances from a mixture. Examples of magnetic substances are iron, steel, nickel and cobalt.

For example

A magnet can be used to separate iron from sulfur in a mixture of iron and sulfur.

Sublimation*

• It is used when a mixture contains a solid substance which sublimes upon heating. Examples of solid substances which undergo sublimation are iodine crystals, naphthalene (mothballs) and dry ice.

For example

Iodine crystals can be separated from salt crystals by heating the mixture until the iodine crystals sublime.

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