Solubility & Saturation D. Crowley, 2007

Solubility & Saturation  To understand the terms solubility and saturation Sunday, September 20, 2015

Solubility & Saturated  The amount of solute which can dissolve in a solvent is called its solubility  Even soluble solutes (like sugar) cannot keep dissolving forever - you wouldn’t expect a whole bag of sugar to dissolve in a cup of tea  When you get to the point where no more sugar can dissolve, you have reached the saturation point (solute becomes visible in the container)  If a large amount of solute is added to the solvent, eventually no more will dissolve, and we get a saturated solution SoluteSolventSolution

Tea Problems  Old Mrs Fry has a problem – “my builder likes 8 sugars in his tea, and I am running out of sugar – do you think he will notice if I only add 6 spoons?”  Design an experiment to test if ‘old Mrs Fry’ can get away with only adding 6 spoons of sugar to her builders!  Would 10 sugars be even sweeter?

Experiment  You are going to test the saturation points of different solids  You can do this by adding a little solute at a time and stirring it. When no more will dissolve you have reached saturation point  You can calculate the mass of the solid added, by knowing the mass of the solvent and the mass of the saturated solution: - mass solid added = mass saturated solution - mass solvent  Why do you think a solution eventually becomes saturated?  How can you make this experiment fair?

Experiment  Complete the experiment, using the different solids (make sure you test the sugar to help out old Mrs Fry!  Add a small amount of solid, stir and see if it dissolves – if it does, add some more, if not stop there and measure the saturated solution mass  Remember to find the mass of the solvent and also of the mass of the saturated solution (after you’ve added the solute)  Work out the mass of solid needed to be added before the solvent gets saturated

Precision  How could you make this experiment more precise (precise results use a smaller scale to measure, e.g. mm not cm)  We could have used grams added instead of number of spatulas – this way we would know an exact amount (perhaps even using 0.5g per time)

True Or False  Are the statements true or false? If false, can you explain why?  Almost all solids will dissolve in a little water  If you add more solid to a saturated solution, it will dissolve  If you add more solid to an unsaturated solution it will dissolve  If you add more liquid to a saturated solution, more of the solid will dissolve  If you heat a saturated solution, more of the solid will dissolve True False - The solution is saturated - no more solid can dissolve!