Separating Techniques

Question 1

What is a mixture?

Answer 1

A mixture is a substance that is made up of 2 different elements that are not bonded together. (physically combined)

Question 2

What is pure substances?

Answer 2

Pure substances only contain one type of substance and has a fixed boiling point.

Question 3

Impure substances

Answer 3

Contains more than one type of substance and has range of boiling points.

Question 4

What is a solute?

Answer 4

A solute is a substance that will be dissolved into a liquid.

Question 5

What is a solvent?

Answer 5

A solvent is a liquid that has the substance dissolved into it.

Question 6

What is a solution?

Answer 6

A solution is a mixture of solute and solvent.

Question 7

Soluble meaning

Answer 7

Something that can dissolve

Question 8

Insoluble meaning

Answer 8

Something that cannot be dissolved.

Question 9

What is Filtration?

Answer 9

Filtration is the process of separating insoluble solid from liquid/solution. As if something is insoluble it cannot pass through the holes in the filter paper.

Question 10

What is the filtrate?

Answer 10

A filtrate is the liquid in the conical flask after the filtration. So, it is the liquid that had been able to drip down/ pass through the filter paper.

Question 11

What is the residue?

Answer 11

The residue is the insoluble solids from the liquid that has been collected on top of the filter paper.

Question 12

What is Crystallisation/ evaporation?

Answer 12

Separation of mixture of dissolved solids from a liquid/solution. In this method it will evaporate the water and leave the solids behind as crystals. So, if you only want the solid you will use evaporation.

Question 13

Can distillation separate soluble solid and liquid?

Answer 13

Yes, but when we are separating soluble solids from a liquid we will most commonly use crystallization. However, if you want both the liquid and the soluble solid separated as finished products, then you will use distillation method.

Question 14

What is Distillation?

Answer 14

Distillation is the separating a mixture of liquids by boiling points. The liquid in the mixture with the lowest boiling point will evaporate first (water).

Question 15

Why does the dissolved solid remain behind and turn into crystals instead of evaporating with the water?

Answer 15

The liquid will turn into gas first because it have a lower boiling point. After you will turn of the heat source. This means the dissolved solid will remain in the evaporating basin as it has a higher boiling point. And when cooled down it will freeze and turn into crystals.

Question 16

Explain how the condenser works?

Answer 16

In the middle of the condenser there is a middle tube where the water vapor travels. Outside the condenser it has water jacket or cold water going in and out around the middle tube to keep it cool for condensation process.

Question 17

What is Chromatography?

Answer 17

Chromatography separated a mixture of liquids by how much they dissolve in the two phases. Substances are separated by how much they are attracted to either the mobile/stationery phase.

A substance will high solubility will travel further up the paper with the solvent as they are more attracted to the solvent.

Question 18

Explain how chromatography works?

Answer 18

The solvent moves up the paper and carries the ink with it. The more up the int travel it is more soluble and attracted to the solvent. If it does not move that much is means it is less soluble in the solvent and more attracted to the stationary phase.

Question 19

What are the two conclusions you can draw from chromatography investigation?

Answer 19

1. How many substances are in the mixture- The number of spots above the starting position.
2. What the substances are in the mixture- Compare the heights (R.F) of the spots in the mixture to the standards.

Question 20

What are the most common mistakes in chromatography?

Answer 20

1. Using a pen to draw the base line. As pens contain ink that will be dissolved in the solvent. This means the ink will rise up on the paper, so you won’t be able to identify the starting position.

Therefore pencil should be drawn, as graphite does not dissolve in water/solvent.

Question 21

What are the most common mistakes in chromatography?

Answer 21

Another mistake is placing the chromatography paper too deep into the solvent so that the spots are under the solvent. As then the spots will dissolve in the water and not go up.

Question 22

What is the Retention Factor?

Answer 22

The retention factor is the proportion that the spot moved compared to how much the solvent moved.

RF = spot moved/ distance solvent moved

Question 23

How to find the retention factor?

Answer 23

1. All distances are measured from the start line.
2. Measure to the center of the spot.
3. Rf values have no units