We see an experiment to demonstrate how minerals dissolve in water. We also see which minerals and metals are found in different types of water. Water is poured into a flask and we see what happens when it starts to boil. As the water heats up, it starts to evaporate. The gas travels out of the flask and into a cold tube. The water vapour condenses and drops out as a liquid. The scientist is then able to look at the minerals contained in the sample of water and explain how minerals are dissolved in water as it flows through the ground.

This clip is from:
Science Clips, Changing State
First broadcast:
11 October 2007

After watching this clip students could draw a labelled diagram of the experiment carried out. They could also annotate this diagram with flow arrows and explanations of the processes taking place. Students could then discuss whether water taken from the ground, with calcium and iron in it, is safe for us to drink.

Students could be presented with three or four beakers of liquid (e.g. mineral water, tap water, lemonade, water with soil mixed in). Pose the question: "Is this liquid safe to drink?" Take answers from the students, highlighting the danger of drinking unknown solutions. Students could then be challenged to test whether there is anything dissolved or mixed in the water. This could provide an opportunity for their knowledge of filtering and evaporation to be taught, tested or assessed. Once the students have carried out the physical processes, they could discuss the residues and identify the original liquid.