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This is a compilation of clips set to a background of music and based on the theme of changing materials. It includes images of fireworks exploding, demolition of tower blocks, a volcano and magma flowing, a time lapse sequence of a cake being baked, a candle melting, toffee in both liquid and solid form, melted metal being cast, a rusted metal sculpture, a match burning, wood, coal, a burning building and a forest fire. Reversible and irreversible changes are demonstrated. Note: There is no narration in this clip.

Challenge individual pupils to pause the clip while viewing it, at any examples of reversible changes. Molten metal, for example, will solidify as it cools, but could be melted again. By contrast, the fireworks shown in the clip can explode only once. The children could be encouraged to use the terms “solid”, “liquid” and “gas” when describing all these changes. After viewing, ask pupils to estimate the number of irreversible changes they saw. Replay the clip to check. Pupils could go on to film examples of reversible and irreversible changes in the world around them: for example, water put into ice cube trays and frozen (reversible), or a birthday cake candle being burned (irreversible). They could play their own clips to the class.