Waterworks

Waterworks: make potable water and watch what each step takes out

This free game is part of our AQA GCSE Chemistry (8462) course for exams in EXAM YEARS 2027-2029.

Potable water for AQA GCSE Chemistry

AQA GCSE Chemistry (8462) spec point 4.10.1.2 asks you to distinguish between potable water and pure water, describe the differences in treatment of ground water and salty water and give reasons for the steps used to produce potable water. In a textbook it is a list of steps. The hard part is seeing what each step actually removes, and why some water needs one treatment and some needs another.

In Waterworks you are the engineer at County Water. You lay glass pipes across a model landscape, from a water source, through the treatment works you choose, into a town. Then you open the valve and watch the water flow. Brown solid bits, green microbes and white dots of dissolved salt travel through the glass, and each works takes out what it can. Whatever is left reaches the tap and gets tested.

Fresh water: filter beds, then sterilise

In the UK, rain provides fresh water, which has low levels of dissolved substances. It collects in rivers, lakes and the ground. Level 1 starts with river water and only the filter beds: layers of sand and gravel that hold back the solid bits that are not dissolved. The water comes out clear, but the tap test still finds microbes, because some are small enough to get through. Clear is not the same as safe.

So the water must be sterilised. The game has all three sterilising agents in the spec: a chlorine works, an ozone tower and an ultraviolet light reactor. Level 2 adds a reservoir and a borehole that pumps up ground water, and teaches the order: filter first, then sterilise, because solid bits can shield microbes and ultraviolet light cannot shine through cloudy water.

Salty water: desalination and energy

Level 3 is a dry island where the river has dried up. The only water is the sea, which has high levels of dissolved salt. Send it through the filter beds and the salt goes straight through, because it is dissolved: a classic exam mistake. You need desalination, either distillation (the water is boiled, the steam leaves the salt behind and is condensed) or reverse osmosis (pumps push the salty water through membranes that hold back the salt). Watch the energy bar jump: both processes need large amounts of energy, which is why desalination is only used when fresh water is limited.

Potable is not pure

Every tap test shows the dissolved salt left in the water. Fresh tap water still has about 0.3 g of dissolved substances in every dm³. That is a low, safe level, so the water is potable, but it is not pure in the chemical sense, because pure water would be water and nothing else. A quick check after level 1 makes sure you can explain the difference in an exam.

Four levels, about 8 minutes

Level 1 has no clock and a guided first pipe. From level 2 the valve opens on a timer and the water chases your pipe, so you have to keep ahead of it. Level 4 is a 120-second drought summer: sometimes the river is too low or the ground water is used up, so you choose the right source for the conditions. Use fresh water when you can and desalinate only when you must, or you lose points for wasted energy. Wrong routes cost points and come with a clear explanation, and the results screen recaps the whole topic, including a ground water vs salty water comparison. It works with a mouse, touch screen or keyboard and saves your best score.