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Chemistry

Solutions

Dissolving table salt in waterDissolving table salt in water 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 large grains or 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 substance that dissolves, usually a crystalline solid like table salt, is called the solute. The substance it dissolves in, usually a liquid such as water, is the solvent. The solute in the solvent is known as a solution. When no more solute can be dissolved, the solution is said to be saturated.



The Dead Sea, a saturated salt solutionThe Dead Sea, a saturated salt solution

Ions

When substances dissolve, their atoms or molecules usually gain or lose electrons. For example table salt, sodium chloride (NaCl), dissolves and breaks apart into its atoms of sodium (Na) and chlorine (Cl). Sodium loses an electron and becomes positive, while chlorine gains an electron and becomes negative. Atoms which are positive or negative are known as ions. Many solutes form ions.


Men panning for goldMen panning for gold

Mixtures

Fizzy, or carbonated, drinks are all based on solutions of carbon dioxide in water. The bubbles are not the dissolved gas, but small pockets of carbon dioxide that are released from solution. The dissolved gas itself is not visible.

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