Separation techniques

Separation Techniques

Year 7

Pure Substances

• Pure substances contain only one substance, with no others mixed in

• They cannot be separated by physical means

• Salt, Sugar, Water, Gold, Hydrogen and many more

Mixtures

• Mixtures are made from two or more pure substances mixed together

• Mixtures can be separated using a variety of separation techniques

• How would you separate the red lollies in the picture?

Separation Methods

• Separation methods are ways to break apart mixtures into individual substances

• Some mixtures have large substances that are easy to separate

• Others contain small substances and can’t be easily separated

Multiple Select

What is a solution?

• is a mixture of one substance that does not dissolve in another

• is a mixture of one substance spread evenly throughout another and is transparent

Multiple Choice

What is a suspension?

• a mixture of one substance₁ which does not dissolve in another

• is a mixture of one substance spread evenly throughout another and is transparent

Multiple Select

Which two properties describe a colloid?

• Colloids are heterogeneous mixtures; however, they look homogeneous

• Colloids are homogeneous mixtures in which particles do not separate

• The dispersed particles of a colloid mix evenly in a mixture but are larger than those in a suspension

• The dispersed particles of a colloid are smaller than those of a suspension, but larger than those of a mixture

Multiple Choice

The Tyndall effect is ...

• ... the reflection of visible light by colloidal particles

• ... the scattering of light by a medium containing small, suspended particles

• .. the refraction of visible light by small, suspended particles

• .. the scattering of visible light by the larger particles in a suspension

Multiple Choice

Which of the following solutions does not show Tyndall effect?

• Milk

• Starch Solution

• Ink

• Sugar Solution

Milk is a colloid - it contains tiny globs of butterfat, which are suspended throughout the liquid.

​​Milk

Starch solution is a colloid - the particles form a shell with the water molecules preventing the particles from aggregating when they collide

​​Starch solution

​Ink is a colloid - the particles never settle to the bottom and do not completely dissolve, and show the Tyndall effect.

​​Ink

Sugar completely dissolves in water and is therefore a solution

​​Sugar Solution

• ​Butter and mayonnaise are examples of a class of colloids called emulsions.

• An emulsion is a colloidal dispersion of a liquid in either a liquid or a solid.

• Oil and water can also be a stable emulsion in the presence of an emulsifying agent. In the case of mayonnaise, egg yolk is this agent.

​

Solutions, Suspensions and Colloids

​Colloid or Suspension?

Solutes & Solvents

• A substance which is added to a liquid is called the solute. It is often a solid. (sounds like 'solid')

• The liquid which the solute is added to is called the solvent. (sounds like 'dissolve')

Multiple Select

Identify Solvent and Solute for:

Saltwater

• Solute: Water

• Solvent: Salt

• Solute: Salt

• Solvent: Water

Multiple Select

Identify Solvent and Solute for:

Sugar and Water

• Solvent: Water

• Solvent: Sugar

• Solute: Sugar

• Solute: Water

Multiple Select

Identify Solvent and Solute for:

Sand and Water

• Solute: Sand

• Solvent: Sand

• Solvent: Water

• Solute: Water

Multiple Choice

The mixture of sand and water is a ...

• Solution

• Suspension

Soluble & Insoluble

• A substance that is able to dissolve in a liquid is considered to be soluble. 

• If a substance cannot do this it is called insoluble.

Multiple Choice

Which substance in the video was Soluble?

• Sand

• Chalk

• Copper Sulphate

• Flour

Watch the video on the next slide

• Watch/listen carefully at 1:30

Multiple Choice

The filtrate is ...

• the mixture of sand and saltwater put in the filter

• the substance that is caught in the conical flask (the saltwater)

• the mixture of sand and salt

• the substance that remains in the filter paper (the sand)

Multiple Choice

After separating the mixture of sand, salt & water...

• the salt is in the evaporating basin, the water escaped in the air, and the sand is in the filter paper

• the salt is in the evaporating basin, the water escaped in the air, and the sand is in both, the filter paper and the beaker

• the salt and water escaped in the air, and the sand is in the beaker

• the sand and water escaped in the air, and the sand is in the filter paper

Filtration

• Filtration is a process that separates solids from liquids

• For this method, a filter is used that allows the fluid to pass through but not the solid. 

• The fluid that passes through the filter is called the filtrate.

Multiple Choice

Granite is a rock type and can be separated by physical processes. Therefore granite can be described as a ...

• compound

• element

• solute

• mixture

• suspension

Multiple Select

The video showed that Iodine

• dissolves in water

• is insoluble in water

• dissolves in isopropanol

  (an alcohol)

Sparingly soluble:

If you need 30-100 ml (milli-litre) of solvent to dissolve 1g of solute

Multiple Choice

About 1.7 gram of Calcium Hydroxide dissolves in 1 Litre of water. Calcium Hydroxide is therefore

• soluble

• saturated

• insoluble

• sparingly soluble

• sparingly insoluble

Multiple Choice

Which image depicts Decantation?

Multiple Choice

Which image depicts Evaporation?

Multiple Choice

Which image depicts Filtration?

Multiple Choice

Which displayed method can be used to separate a solution of sugar water?

Crime Scene Investigation

You found a disturbing note and some pens. One of the pens was used to write the note. How can you find out who committed this crime?

Multiple Choice

To find the person who wrote the note, you can use the following separation technique to identify the pen that was used:

• Filtration

• Distillation

• Chromatography

• Evaporation

• Decantation

Foam

A foam is a substance made by trapping air or gas bubbles inside a solid or liquid.

Distillation

Watch the following video and pay special attention to time 4:15 and following

Multiple Choice

The distillation can separate two liquids, because the water has a ...

• lower boiling point than the other liquid

• a lower melting point than the other liquid

• a higher melting point than the other liquid

• a higher boiling point than the other liquid

Distillation

Distillation is the process of separating the substances from a liquid mixture by using selective boiling and condensation.

Distillation can be used if the liquids have widely different boiling points

Multiple Choice

Alcohols are soluble in water. To separate alcohol from water, we can use distillation, because water and alcohol ...

• are insoluble

• can actually not be separated

• have different boiling points

• is a suspension

Interpret the graph

The graph shows the solubility of salt as the temperature increases.

How many spoons of salt is at 35°C?

_{(Answer the question on the next slide)}

Multiple Choice

How many spoons of salt was at 35°C ?

• 6

• 6.5

• 7

• 7.5

• 8