Chemistery

Keep stirring sugar into a glass of iced tea and at some point it stops disappearing. A little pile settles at the bottom and simply refuses to go. The water hasn't got tired — it's full. The short answer: a saturated solution contains the maximum amount of solute that will dissolve in a given solvent at a given temperature. Add more and it just sits there undissolved, because dissolving and re-crystallising are happening at exactly the same rate. The three kinds of solution Type How much solute What you see Stable? Unsaturated Less than the maximum More solute still dissolves when added Yes Saturated Exactly the maximum Extra solute sits undissolved at the bottom Yes Supersaturated More than the maximum Clear, but crystallises at the slightest disturbance No — metastable What "saturated" really means The undissolved crystals at the bottom of a saturated solution aren't doing nothing. At the microscopic level, two processes are ...

Salt vanishes into water in seconds. Oil sits on top and sulks no matter how hard you stir. Sugar dissolves faster in hot tea than iced tea. All three are the same question wearing different clothes: what makes something dissolve? The short answer: solubility is the maximum amount of a substance that will dissolve in a given amount of solvent at a particular temperature. Whether something dissolves comes down to one rule — "like dissolves like" — because polar solvents pull apart polar and ionic solutes, and nonpolar solvents dissolve nonpolar solutes. What solubility actually measures Solubility is a number, not a yes/no. It's usually quoted as grams of solute per 100 g of water at a stated temperature : Table salt, NaCl: about 36 g per 100 g of water at 25 °C Sugar (sucrose): about 200 g per 100 g of water at 20 °C Chalk, CaCO₃: about 0.0013 g per 100 g of water at 25 °C Notice that chalk isn't strictly insoluble — it's just so poorly soluble that w...