To measure the amount of nickel in some industrial waste fluid, an analytical chemist adds sodium hydroxide solution to a sample of the fluid and collects the solid nickel(II) hydroxide product. When no more is produced, he filters, washes and weighs it, and finds that has been produced. The balanced chemical equation for the reaction is:

gas

explanation:

smoke is the matter of a gas

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.