Materials and Mixtures II

Two groups of pupils investigated the factors affecting the time taken for an indigestion tablet to dissolve in 100 cm3 of water. Group 1 recorded their results in the table.

What factor did group 1 change as they carried out their investigation?

Before the investigation, group 1 made a prediction. They found this prediction was supported by the results in the table. What prediction did group 1 make?

Group 2 investigated how the temperature of the water affects the time taken for a whole tablet to dissolve. Here are their results.

What factor did group 2 change as they carried out their investigation?

What pattern do the results recorded by group 2 show?

Look at the results presented by group 1 and group 2. Both groups used the same type of tablet. Estimate the temperature of water used by group 1. ............°C

Susie used chromatography to identify the coloured substances in the ink from a felt-tip pen. She used:

• green ink

• blue ink

• purple ink

• ink from her felt-tip pen.

She used water as the solvent.

Look at the diagram above.

Which colours were present in the ink from the felt-tip pen?

How many coloured substances were there in green ink? ...........

How can you tell?

Susie placed the spots of ink on a line on the chromatography paper as shown in the diagram. To draw the line, Susie had to choose a felt-tip pen or a pencil.

Which one should she use? .............................................................

Give the reason for your answer. ..................................................................................................

Susie used water as the solvent in this experiment. When she repeated the experiment with a different set of pens, it did not work. She then used ethanol instead of water.

Suggest why the experiment worked with ethanol but not with water.