Stir a teaspoon of table salt into a glass of water, and the salt disappears. However, tasting the water shows the salt is still there. It has dissolved. The crystals of salt have broken down into their individual atoms. These are too small to see and float about freely among the molecules of water. The liquid, known as the solvent, and the salt dissolved in it are together known as a solution.

Stalagmites and stalactites

Limestone is made of calcium carbonate, a mineral (a chemical that makes up rock) that dissolves easily in water. Water dripping from a cave roof leaves a tiny amount of the dissolved minerals behind as it falls.

Shaking salt and sand together produces a mixture. This is different from a solution. In a mixture, substances intermingle but they do not dissolve. Add water to the mixture and the salt dissolves. It is soluble. The sand grains do not dissolve. They are insoluble.

Suspension

With some substances, for example powdered chalk, the particles are small enough to remain floating in a liquid for a short time (producing a cloudy mixture) before sinking to the bottom. This kind of mixture is called a suspension.