WHEN acids meet alkalis

You will need
* trays (one for a group of up to three)
* metal spoons and stirring sticks
Please, stir the citric acid with the lollipop sticks and the baking soda with the spoons
* goggles and gloves for kids with scratches, wounds or bitten cuticles
* measuring jugs (at least 500 ml capacity)
* measuring cups (at least 100 ml capacity)
* soap dispensers
* citric acid
* a set of measuring spoons for each team
* baking soda
* food colouring
* empty 500 ml bottles

* Make sure everyone is wearing goggles. Get each team to pour 200 ml of water in the large measuring jugs

* Now, get them to select the largest spoons in the set and get them to put 1 spoonful of baking soda in the water (remind them of the rim trick and chant, stir and stir and stir).
* Pour the water in the bottle, and now get them to pour 80 ml water in the small measuring cups, get them to squirt one squirt of liquid soap each in the small cups, add food colouring (one pipette each) and stir, stir, stir.

* Bring their attention to the bubbles in the foam; that's the gas (CO2) trapped in soap

YOU ALONE: gently shake the bottles left to right when the chemical reaction ends and tell them to watch as the chemical reaction STARTS AGAIN