Which of the following provides evidence that a chemical change has taken place? a). the original substance can be recovered by physical processes b). a gas is formed when tow liquids are mixed c). some pieces of substances get smaller or disappear d). one substance dissolves in another

Answer : Option B) A gas is formed when two liquids are mixed.

Explanation : In this example a gas is forming as a result of mixing two liquids, so, changing of state can be clearly noticed, also there is a new substance which is produced and the reaction is also irreversible (i.e. it cannot be easily recovered to the starting reactants by any physical process). Hence, Option B is correct answer.

i belive it is water