1.1. Mixtures of substances can be separated using different techniques.

Which of the following is a mixture of substances?

1.2. Figure 5 shows the apparatus that a student set up to obtain pure water from ink.

There are three mistakes in the way the apparatus has been set up.  

Figure 5

i) One mistake is that the bulb of the thermometer is too low.

The bulb of the thermometer should be level with the side arm.

Give a reason why the bulb of the thermometer should be level with the side arm. 

(1)

ii) State one other mistake in Figure 5.

(1)

1.3. Paper chromatography is used to separate the substances in five different food colourings, P, Q, R, S and T.

Figure 6 shows the chromatogram at the end of the experiment.

Figure 6

i) The steps needed to carry out the chromatography experiment are listed below. They are not in the correct order.

1. leave the solvent to rise up the paper

2. put solvent in the beaker

3. draw a start line on the piece of paper 3

4. place the paper in the beaker

5. remove the paper when the solvent is near the top

6. put small spots of the food colourings on the start line

List the steps in the correct order.

The first two steps have been done for you. 

(2)

ii) Explain, using Figure 6, which food colouring contains the greatest number of coloured substances. 

(2)

iii) During chromatography of the food colourings, the solvent front moved 8.00 cm and the food colouring R moved 2.30 cm.

Calculate the R_f value for food colouring R.

Give your answer to two significant figures. 

(2)