Assuming it's a perfect gas, we have PV=nRT hence if T goes down, V goes down up. The volume will decrease.
Filtration
distillation
crystallization
chromatography
The answer is (4) synthesis. Synthesis reaction means that two or more reactants combine directly to one production. Substitution or single replacement means that one element of a compound is replaced by another element. Double replacement means that two ionic reactants exchange ions to form two new productions.
Chemical equations are to be balanced to be able to follow the law of conservation of mass where it says that mass cannot be created or destroyed. Reactions should be that the mass of the reactants is equal to the mass of the products.
