Answers are:
1) It can be separated by physical methods.
2) It can appear different from different sources.
3) It cannot be described by a chemical symbol or formula.
Mixture is composed of at least two substances.
Pure substance is made of only one type of atom (element) or only one type of molecule (compound), mixtures and solutions are made from two or more types of pure substances.
Mixtures can be separeted y physical means, while compounds cannot.
There is a definite recipe to make each mixture, because composition of mixture can vary.