Which of these is a pure substance and why? A Milk, because every portion of the matter is the same, and its components can only be separated chemically. B Coffee, because every portion of the matter is the same, and its components can only be separated chemically. C Salt water, because every portion of the matter is the same, and its components can only be separated chemically. D Carbon dioxide, because every portion of the matter is the same, and its components can only be separated chemically.

d carbon dioxide

Explanation:

Carbon dioxide is a pure substance that is a compound (two or more elements bonded together).

c- cold periods in earth's history during which glaciers covered much of the surface.

explanation:

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).