Great question! There are a lot of really good chemical reactions that a 9-10 year old could demonstrate to a class safely. The question is which one is likely to be new to the crowd. For your daughter I'd recommend the "Invisible Ink" reaction:
http://discoveryexpress.weebly.com/homeblog/invisible-ink-how-acid-and-heat-can-reveal-messages
You will use lemon juice (acid) and a clothes iron set at its highest setting (heat) to demonstrate how the acid in the lemon juice breaks down the cellulose in the paper to more combustible compounds. She could even go on to use other compounds, as suggested in the exercise.
A few others you could try:
http://discoveryexpress.weebly.com/homeblog/what-is-solubility
http://discoveryexpress.weebly.com/homeblog/use-vinegar-and-baking-soda-to-blow-up-a-balloon
http://discoveryexpress.weebly.com/homeblog/invisible-ink-how-acid-and-heat-can-reveal-messages
You will use lemon juice (acid) and a clothes iron set at its highest setting (heat) to demonstrate how the acid in the lemon juice breaks down the cellulose in the paper to more combustible compounds. She could even go on to use other compounds, as suggested in the exercise.
A few others you could try:
http://discoveryexpress.weebly.com/homeblog/what-is-solubility
http://discoveryexpress.weebly.com/homeblog/use-vinegar-and-baking-soda-to-blow-up-a-balloon
