Intrinsic motivation plays a unique mediating role in student academic performance. An inquiry-based learning (IBL) physics practical is studied in terms of effects on secondary school students’ intrinsic motivation towards performing science practicals. After performing IBL experiments on ionizing radiation, 38 secondary school physics students were interviewed and expressed their need for support in two main areas: the inquiry process and non-salient tasks, i.e., operating the equipment. A quasi-experiment was then carried out. One experimental group received both a revised worksheet and a video (N=88), the other only received the worksheet (N=67). Students performing the same practical on the basis of a step-by-step instruction sheet were used as a control group (N=87). Results show significant larger gains in intrinsic for the IBL groups. The results point to the advantages of using an IBL approach for practicals, provided appropriate scaffolding is used.