C2: Separating mixtures

What is a mixture?

A combination of two or more substances that are not chemically joined 

What does the word ‘pure’ mean?

A substance made up of only one element or compound, and is not mixed with any other substances.

What is a solute?

A solid substance that dissolves in a liquid to form a solution. 

What is a solution?

The mixture of the solute and solvent.

What is a solvent?

The liquid that dissolves the solute 

Sodium chloride dissolves in water to form sodium chloride solution. Name the solute and the solvent.

Solute: Sodium chloride        
Solvent: water   
Solution: Sodium Chloride

What is the name of the technique used to separate sodium chloride crystals from a solvent (water)?

Crystilisation

What does the word insoluble mean?

Cannot be dissolved

Name the technique used to separate an insoluble substance from a solution?

Filtration

Why do these insoluble substances not pass through the paper?

As they are solid particles and are too large to fit through/ pass through the paper

What do we call safe drinking water?

Potable water

Explain the main stages in making water safe to drink

1. Grit and other small insoluble particles settle out by sedimentation
   
   2. Very small insoluble particles are removed by filtration
   
   3. Chlorine is added to kill harmful bacteria. This is called chlorination

What is chromatography? What does it separate?

A technique used to separate the components of a mixture based on their different solubilities in a solvent.

How do you calculate Rf value?

Distance travelled by a substance/distance travelled by the solvent

Why is pencil used as the baseline?

Because the pencil is insoluble, meaning it won’t dissolve.

. Where should the water not go above in chromatography? Explain why.

Prevents the ink or dye dissolving in the water before the separation process begins.

What is the mobile phase?

Moves and carries the substance in the mixture to be separated

What is the stationary phase?

Part of a separation process that does not move

Name the method used to separate a solvent from a solution.

Distillation

Name the state change that happens in a round bottom flask in distillation.

Evaporation (or boiling)

Explain the process of simple distillation (IMPORTANT)

Salt soultion is heated in a flask. Water evaporates and water vapour leaves the salt solution. Water vapour then travels into a condenser. The condener cools the water vapour. It condenses to form distilled water.

Name the physical property of different liquids that fractional distillation relies on. 

Difference in boiling points

What happens in the condenser during distillation?

Cools the water vapour to condense turning the vapour into a liquid to form distilled water. 

What is fractional distillation?

Another technique used to separate out mixtures of a liquid and boiling points.

What is electrolysis?

The breaking down of ionic compounds using electricty

What is the solution called in which needs to be separated?

Mixture

What are the 2 metals rods called suspended in the solution?

Electrodes

What are the positve one called that are attracted to the cathode

Cation

What are the negative one called that are attracted to the anode

Anion

If a halogen is present, will oxygen or the halogen be attracted to the positive electrode?

Anode

If potassium is present, will potassium or hydrogen by attracted to the negative electrode?

Cathode due to Metals having opposite charges

Why should Electrolysis only take place in an aqueous (dissolved in water) or molten solution.

This is because ions are free to move in a liquid or molten state meaning they can conduct electrcity whereas, if electrolysis was in a solid state ions are in a fixed lattice strucuture unable to move and therefore cannot conduct electrcity.

What piece of important equipment will you need for electrolysis to take place that supplies the electricity?

Power supply