The boys were given a 'Bath Bomb' kit my Mum picked up in a charity shop - brand new! It provided a great morning's chemistry work with concoctions of citric acid and bicarb producing fizzing bath bombs to add to my eldest son's soap making initiatives. We also managed to get a pipette of water inside a balloon with the same blend ready to be activated by pressing the balloon, thus inflating it without any air. I asked the boys what the balloon was filled with. 'Carbon dioxide gas,' they replied without hesitation. The cold feel of the gas inside the balloon and the fizzing sound effects made this a multi-sensory experience. Great!