To remove soluble impurities, first, by doing solubility tests, a suitable solvent is chosen (high solubility in hot solvent, low solubility in cold solvent). The soluble impurities are then removed as follows: the desired compound along with the soluble impurities are dissolved in a MINIMUM of near-BOILING solvent.
Free body diagrams are used to describe situations where several forces act on an object. On the other hand Vector diagrams are used to resolve (break down) a single force into two forces acting as right angles to eachother
