what happen if you wash the crystals with hot water?

why dry overnight? the longer period of time ensures all the water in the crystal has evaporated.

i was asked why i needed to wash with cold water.  i thought it would be harder to solubilize (?) in colder water so it would be used to remove insoluble impurities, but the answer was to remove soluble purities.  so would i precipitate to remove insoluble impurities?

also, does drying overnight help crystallize more?  i'm not sure why that part was written in the experiment either.  thanks again for the help.

cold water presumably doesn't dissolve much (if any) of your desired product, but does dissolve some impurities present in the reaction mixture. This is the reason for washing with cold water. So using hot water to wash your product may well result in a lot more of your product dissolving, and being lost.

To remove insoluble impurities from a reaction mixture often involves filtering the mixture so that your product is dissolved and your impurities are caught in the funnel.

If both your product and the impurities are insoluble, this is much more tricky to purify. This may involve finding suitable conditions to recrystallise your product - i.e. finding a solvent system which dissolves everything when hot, but only the impurities when cold.

Failing this, a standard method of purification involves taking advantage of the different polarity of molecules. You can dissolve everything in as non-polar a solvent as you can then separate the different compounds by using chromatography, usually using a column of silica. The fundamental premise here is that different compounds 'stick' to the silica more or less strongly. you can then use solvents to remove the products at different times - a less polar solvent will remove a less polar compound but leave a more polar one 'stuck' to the silica.