ilovebacteria - Grow your own crystals!

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Meet the Microbes

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Welcome to ilovebacteria.com formally known as Ratlab.co.uk!

Do try this at home	Back to experiments
Grow your own crystals	Why does this work?
Learn about solubility, evaporation and then eat your experiment when you've finished with it! Ingredients String (not nylon) Cane Sugar Pencil Water Food coloring Recipe Boil the water and stir in sugar until no more will dissolve Allow to cool a bit and then add food coloring and tip into a glass Balance a pencil on the top of a glass filled with the sugar solution and suspend a piece of string/cotton into the liquid. Alternatively, you could put a chop stick or cocktail stick into the liquid. When your crystals have formed (it takes a few days), remove them, let them dry and then you can eat them. For bigger crystals, it sometimes helps to make a seed crystal first. To do this, dissolve the sugar as before then let the solution sit until small crystals form in the bottom of the glass. Remove these and tie to a piece of nylon thread (new crystals won't form on nylon, only on the seed crystal) and hang in the sugar solution as before. Remove crystals that form at the bottom of the glass to allow your crystal the best possible chance! Tip: If you want to cover the top of the glass, use one sheet of some kitchen rol l- you still want evaporation to occur.	If you were to test it, you would find that the solubility of sugar into water increases with temperature. This was the point of heating the water while dissolving the sugar. At room temperature, you can dissolve around 200g sugar in 100ml water and after this, no more sugar will dissolve - this solution is known as a saturated solution. If you heat the mixture to 100 degrees Celsius, nearly 500g of sugar will dissolve and this solution is said to be supersaturated. Once cooled, this solution is unstable because the water is holding more sugar than it really wants to be. So sugar starts coming out of solution as the temperature drops. In this experiment, the initial cooling of the liquid lead to the formation of the initial crystals and over a few days, evaporation of the water reduced the volume and therefore the capacity for sugar, and led to more sugar coming out of solution. The crystals tend to form on existing crystals and this is why you end up with a big lump of sugar at the end of the experiment. The process of crystallisation is shown in this picture. You begin by adding liquid to a solid, shown in the first picture. By heating this, we can force the solid to dissolve past its saturation point to form a saturated solution, shown in the third picture. As the temperature falls and liquid evaporates, crystals are formed.

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