Effect of temperature on solubility
The hypothesis that as the temperature of the water increases, the amount of substance dissolved in the water also increases, is proven to be true.
Solubility of a substance in a solvent can be increased or reduced by adding another substance. For example, adding salt in a solution saturated with sugar will enable more sugar to be dissolved in the solution. This technique is used in candy making. .
Try to repeat the experiment by using other substances like calcium chloride, potassium permanganate or iron sulfate.
The experiment can also be repeated using different solvents like alcohol or benzene.
Effect of temperature on solubility - http://preparatorychemistry.com/Bishop_solubility_temperature.htm
Solubility of substances in solution - http://chestofbooks.com/food/science/Experimental-Cookery/Solubility-Of-Substances-In-Solution.html
Solubility in water - http://www.lenntech.com/air-purification/gas-purification-techniques/solubility-in-water.htm
Basic safety requirements