EVERYDAY SCIENCE

Detailed explanation-1: -In simplest terms, a chemical change (or chemical reaction) occurs when two substances are mixed together and transform into a third substance. Not all substances react chemically when mixed together, however. For example, some substances, when mixed together, remain simply a mixture of those two substances.

Detailed explanation-2: -A compound is a substance that contains two or more elements chemically combined in a fixed proportion. The elements carbon and hydrogen combine to form many different compounds. One of the simplest is called methane, in which there are always four times as many hydrogen atoms as carbon atoms.

Detailed explanation-3: -A combination reaction is a reaction in which two or more substances combine to form a single new substance. Combination reactions can also be called synthesis reactions. The general form of a combination reaction is: A+B→AB. One combination reaction is two elements combining to form a compound.