SOLUTIONS

WHAT IS A SOLUTION? When a substance dissolves, it goes into a solution, a mixture in which one substance is evenly mixed with another substance. The substance that dissolves in a solution is called the solute. The solvent is the substance in which a solute dissolves. A substance that dissolves in another substance is soluble in that substance.

Particles in a Solution - Understanding Solutions Particles in a Solution When a solution forms, particles of the solute leave each other and become surrounded by particles of the solvent.

UNIVERSAL SOLVENT Water is called the universal solvent. This is because many types of substances dissolve in water.

How can you change the rate at which substances dissolve? Stirring the solution will make the solute dissolve faster. Temperature of the liquid solvent affects how fast a solid dissolves. Increasing heat will make the solute dissolves faster. Surface Area affects the rate at which a solid solute dissolves. Smaller size particles can help dissolve solids faster.

WHAT IS THE CONCENTRATION OF A SOLUTION? Dilute solutions are weak solutions that contain a small amount of solute. Concentrated solutions are strong solutions with large amounts of solute in the solution. You can dilute a strong solution by adding more solvent. Usually adding more water. Unsaturated solutions can hold more solute at a given temperature.

Saturated solutions contains all the solute it can hold at a given temperature. Adding more solute to a saturated solution will go to the bottom of the solution. Precipitate is the undissolved solid at the bottom of a saturated solution. Supersaturated solutions hold more solute than it can normally hold at a given temperature. Making rock candy is an example of a supersaturated solution,

A. Concentration UNSATURATED SOLUTION more solute dissolves no more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form concentration

B. Solubility Solubility maximum grams of solute that will dissolve in 100 g of solvent at a given temperature varies with temperature based on a saturated solution

Temperature and Solubility - Concentration and Solubility Temperature and Solubility The solubility of the compound potassium nitrate (KNO3) varies in water at different temperatures.

Solubility Solubility Curve shows the dependence of solubility on temperature

HOW DO SOLUTES AFFECT FREEZING AND BOILING POINT? The amount of solute dissolved in a solvent affects the freezing point of the solvent. Adding solute lowers the freezing point of a solvent. Throwing salt on an icy sidewalk is an example of lowering the freezing point of water. The boiling point of a liquid solvent is increased by adding a solute. Adding salt to water is and example of increasing the boiling point of water .

Effects of Solutes on Solvents - Understanding Solutions Effects of Solutes on Solvents At 0ºC, pure water freezes, but water mixed with a solute does not. Solutes lower the freezing point of a solvent. Liquid water solution Solid (frozen) water