As an anhydride, It can be prepared by dehydrating its acid, i.e. Acetic acid, by strong dessicant such as Tetraphosphorus decaoxide (P4O10) : P4O10 + 12 CH3COOH ----> 4 H3PO4 + 6 (CH3CO)2O
yes if you pour any kind of liquid
Answering "How can you prepare acetic anhydride at lab?".
Since substances dissolve in liquids, and not the other way around, powders would dissolve more easily.
Powder is considered a solid, not a gas, nor a liquid. it is actually a solid