Chemistry - Topic 2 States of Matter + Methods of separating and Purifying Substances ( Year 9 Autumn)

Solid

-Regular arrangement, particles packed close together -vibrate around fixed position -fixed shape -doesn't exert any pressure

Liquid

-Random arrangement, particles close together -Move around each other -takes up shape of container -can exert some pressure

Gas

-Random arrangement, particles far apart -move fast in all directions -no fixed shape -can exert lots of pressure

State changes

Physical changes that can be reversed

Liquid to Gas

evaporation

Gas to Liquid

condensation

Solid to Gas

sublimation

Gas to Solid

deposition

how can you predict the state of a substance

if you know the temperature, boiling and melting points

Pure substances have…

-Same fixed composition so cannot be separated using physical methods

-same composition so all of it will melt at the same temperature until all of the substance has changed state

A mixture….

-contains elements and compounds that aren't chemically joined so can be separated using physical methods

-doesn't have a fixed melting point

Filtration

separating insoluble solid and liquid (sand and water)

Crystallisation

separating soluble solid from a solution by evaporating the solvent

Why does Crystallisation form different sized crystals

the slower it forms the larger the crystals

Reducing Risks with Crystallisation

-wear safety goggles

-Remove Bunsen burner before fully evaporated to prevent spitting

Chromatography

used to find which coloured compounds a mixture contains

Paper Chromatography

-simpler technique

-some compounds dissolve faster than other so different substances are carried at different speeds and get separated

Solvent

Mobile phase

Paper

stationary phase

Retention Factor

distance moved by substance/distance moved by solvent

Distillation

separates the solvent from the solute dissolved (keeps solvent)

distillation stages

Evaporation Condensing (vapour turns back into a liquid) Collecting

A simple still

Not as efficient because much of the vapour is lost

Fractional distillation

• separates a mixture of liquids -liquids with a lower boiling point evaporate first -mixture will be split into several parts or fractions

What does fractional Distillation use

a column fixed to distillation flask to create a temperature gradient

Reducing risks with distillation

-anti-bumping granules makes liquid boil more smoothly

-safety goggles

Drinking Water

free from substances harmful to health

Labratory Water

free from all substances

Why can't water used for chemical analysis contain dissolved salts?

since it may hide the correct result of the analysis

fresh water can be produced from sea water

with simple distillation

making fresh water drinkable

-sedimentation

-filtration

-chlorination