4.8.1☁️

Question 1

What is a pure substance?

Answer 1

A single element or compound not mixed with any other substance.

Question 2

Do pure substances boil and melt at specific temperatures or random?

Answer 2

Specific.

Question 3

What can you use the melting and boiling point of a pure substance for?

Answer 3

To distinguish them from mixtures / impure substances.

Question 4

What is a formulation?

Answer 4

Is a mixture that has been designed as a useful product, in which each chemical has a particular purpose.

Question 5

How are formulations made?

Answer 5

By mixing the components in carefully measured quantities to ensure the product has its required properties.

Question 6

What are 3 examples of formulations?

Answer 6

Medicines, fuels and paints.

Question 7

What is chromatography?

Answer 7

A method that is used to separate mixtures and can give information to help identify substances.

Question 8

What 2 phases are involved in chromatography and what do each represent?

Answer 8

Mobile phase: solvent as it travels up the paper.
Stationary phase: the paper as it doesn’t move.

Question 9

What does separation in chromatography depend on?

Answer 9

The distribution of the substances between the phases.

Question 10

What is the equation to work out the ratio of distance moved by a compound to the distance moved by the solvent?

Answer 10

RF value = distance moved by substance / distance moved by solvent.

Question 11

How does a separation in mixtures show up on paper?

Answer 11

May separate into different spots, depending on the solvents.

Question 12

How does separation in a pure compound show up on paper?

Answer 12

It will produce a single spot.

Question 13

Required practical 6: chromatography
Key equipment needed:

Answer 13

Beaker, pencil, ink, ruler, pencil, distilled water, chromatography paper, glass spotters

Question 14

Required practical 6: chromatography.
Describe the 7 steps needed to carry out this practical:

Answer 14

• Draw a horizontal line at-least 1-2 cm from the bottom of the chromatography paper, use a pencil.
• Use a small glass spotter to put a dot of each dye/ink/food colouring onto the paper at the bottom pencil line and label them A, B, C, D.
• Pour enough water into the beaker to reach the bottom of your paper. (About 1cm cubed)
• Suspend the paper into the beaker of water
• wait for solvent to travel up the paper and your substances too move. And once they stop moving draw a second line in pencil at the top.
• wait for the paper to dry and calculate the RF values.

Question 15

Why do you use pencil instead of pen to mark your paper?

Answer 15

Because ink would travel up the paper and pencil is insoluble.

Question 16

Why do you pour enough water to reach the bottom of the paper?

Answer 16

Because too much water may cause the substance to travel up the paper randomly and cause a blur.

Question 17

What is the pencil line drawn at the top where the substances have reached of the chromatography paper called?

Answer 17

The solvent front.