I’m going to pour this jug of water into the tray. Listen and watch what happens when the water moves.

Hands up: can moving water do a real job, or does it only make a splash? Could moving water turn a wheel?

You saw moving water push its way across the tray. That push is the force of moving water.

A water wheel is a wheel with paddles that catch that push and turn. The moving water pushes the paddles (a force). That push transfers energy to the wheel so it spins and can do a job.

Later we’ll link the same idea to real power stations in Ireland. If we build a small wheel, what one thing might we change to make it spin faster?

Your group will build a simple water wheel that can spin on a tray.

The axle is the thin stick or straw the wheel spins on. Build in this order: fix the paddles evenly around the hub, slide the hub onto the axle, rest the axle ends on two supports over the tray, then check it spins with a gentle finger push.

Mark one paddle with a small piece of sticky tape so you can count full turns later.

Success looks like this: when you pour water onto the paddles, the wheel turns. Test with a short pour, then stop and wait for the plan step before you change anything.

We want to find out what makes our water wheel spin faster. First we will sort six cards together on the board as a class model. Volunteers help drag each card into Change, Measure or Keep the same while everyone else watches and calls out ideas.

On the board the six cards are: pour height, how strong the flow is, number of turns in the set time, the water wheel, how long we count for, and the jug. Our class model uses pour height as the thing we change. We always measure number of turns in the set time. The whole class will use the same counting time on the class timer (for example 10 seconds).

Then your group chooses for real: pour height or how strong the flow is. On your Investigation Journal page write your plan under these headings: question, prediction, what we change, what we measure, what we keep the same.

Run the fair test your group planned. Change only the one factor you chose. Keep the wheel, the jug and the counting time the same. Count full turns of your marked paddle for each trial and do each setting twice.

The teacher will run short shared 10-second countdowns on the board. Pour only when your tray is ready for that countdown. If you miss a round, wait for the next one. Cover these jobs in your group: pour, count turns of the marked paddle aloud, watch the shared timer, and record. If your group is not four people, double up or share a job.

While another group is pouring, watch and be ready to say whether their test still looks fair.