Heat it, and more will dissolve

Does heat help? (Activity 9.2, a teacher demonstration: take care with the heater.) Put about 50 mL of water in a beaker and check its temperature with a thermometer, say 20 °C. Stir in baking soda (sodium hydrogen carbonate) bit by bit until some is left undissolved at the bottom. The solution is now saturated at 20 °C.

Heat it to 50 °C, stirring. The leftover baking soda dissolves.

Add more until some is left over again, then heat to 70 °C. It dissolves once more.

For most substances, solubility goes up as the temperature goes up.

So a solution that is saturated at one temperature becomes unsaturated when you heat it: it can take more. That's why solubility must always be given with a temperature, and why your over-sweet tea will dissolve the extra sugar if you heat it.

Water has always been the main solvent for medicines in Ayurveda, Siddha and other traditional Indian systems, along with extracts of herbs in water and alcohol, and oils, ghee and milk as solvents.

The chemist Asima Chatterjee used solvents and solutions to pull useful compounds out of medicinal plants, and developed medicines against epilepsy and malaria. She was the second Indian woman to earn a Doctorate of Science (after Janaki Ammal), the first woman to win the Shanti Swarup Bhatnagar Award in chemical science, and was given the Padma Bhushan.