Which of the following is a substance?
A. Sea water
B. Brass
C. Tape water
D. Graphite
E. Sand
In chemistry, a substance refers to a matter which has specific composition and specific properties which do not change. A substance can be an element or a compound. A substance typically has a constant composition, which can not be separated by physical methods. Seawater and sand are not substances, because they have varied compositions and their components can be separated by physical methods.