My Science Investigative Project aims to find out how different kinds of solutions containing different impurities will affect the evaporation rate.
Salt and sugar of equal amount will be dissolved in two beakers of water with the same volume and left under an electric fan to evaporate. The water level will be observed every 4 hours. There will also be a control setup filled completely with pure water. The 2 beakers containing salt and sugar each contain 40ml of water and 10ml of salt or sugar, while the control setup contains 50ml of water. The beakers are placed in such a way that they are an equal distance away from the fan.
After 4 days of investigation it is found that the evaporation rate of plain water is approximately 0.000023ml/hour. The evaporation rate of the salt solution is approximately 0.000019ml/hour and the evaporation rate of the sugar solution is approximately 0.000018ml/hour. Hence, after 4 days, the water volume in the beaker containing plain water is approximately 47.8ml, while the water volume in the beaker containing salt solution is approximately 48.2ml and the water level of the sugar solution is approximately 48.4ml. This is because salt and sugar have different molacular weight.Salt has a molecular weight of 58.44g/mole while sugar has a molecular weight of 342.2g/mole, so if you add them to a solution sugar will have more molecules as compared to salt, hence with more impurites, the sugar solution will evaporate slower than the salt solution. Based on research, i have found out that impurities affect the evaporation rate because it will lower the vapour pressure, which is the measure of the forces exerted on a liquid as the liquid is evaporating to get equilibrim pressure. Hence, with more impurities, less water needs to be evaporate to get equilibrim pressure because the vapour pressure is lower.