Did you ever have indoor fireworks when you were a kid? We did and now we like to use them in the classroom to support the Year 5 Properties of changing materials - explain that some changes result in the formation of new materials, and that this kind of change is not usually reversible, including changes associated with burning and the action of acid on bicarbonate of soda. This is the pack we like and it lasts a few years https://www.amazon.co.uk/B4E-Indoor-Fireworks-2022-Bonanza/dp/B0BF9Z6612
Give each table an indoor firework to look at (remind them not to touch it just observe closely) . Get them to do a pictorial prediction of what they think they will see when its lit and what will be left after it has burned. The in a controlled safe manner – maybe outside so you don’t set the smoke alarms off! Light each firework in a sand tray with water to hand and the children standing well back. Ask the children to notice what the see, smell and hear. Did it match their predictions? Were they surprised? What material do they thin is left? Is it reversible? Our favourite pack can be bought here. Make sure you use a snakes alive as one of your chosen fireworks, as they are a real surprise and challenge the children’s thinking – that fire destroys and nothing is left.