Focus on one type of mechanical weathering: freeze–thaw. Display images of rock split by straight cracks. Explain the idea: water seeps into a crack, freezes and expands, widening the crack; over many cycles the rock splits. Using the slide deck, model this with an animated cross-section.
Set up the model: a sealed container full of water represents a "rock". Model completing the top of the Fair Test Investigation Template — question ("When we change the temperature, what will happen to our rock?"), a reasoned prediction, and the variables (change the temperature; observe how the container changes; keep the container size, water amount and time the same).
As a class, agree the plan and the controlled variables. Groups fill their containers with the same amount of water, seal them in bags, label them, and place them in the freezer. Groups write their question and prediction on the template.
(Next session) Remove the frozen containers and observe: the ice has expanded and cracked/pushed the container. Students record observations and compare with their predictions.
Students complete the Freeze–Thaw Investigation section of the shared template: recording observations, comparing to their prediction, evaluating whether the test was fair, and explaining how freeze–thaw breaks real rock over time.
Exit ticket: explain in one sentence how freeze–thaw breaks rock.