MIXTURES : When two or more substances are mixed together but not chemically joined they are called as mixtures. Mixtures are absolutely everywhere you look. Mixtures form for most things in nature. Rocks, air, or the ocean, they are just about anything you find. They are substances held together by physical forces, not chemical. This statement means that the individual molecules enjoy being near each other, but their fundamental chemical structure does not change when they enter the mixture. The methods of separation of mixtures depend on the constituents of the mixtures. The constituents in a mixture can be separated by easy methods like picking, sieving, or winnowing. You can make a mixture of rice, paper, clips and marbles. These can be separated into different piles of rice, paper, clips and marbles. Some mixtures can be separated by evaporation or condensation.