the maximum amount of a substance that can be dissolved Solubility the maximum amount of a substance that can be dissolved

Solubility Solubility is a physical property. Dissolving is a physical change. In a physical change, substances change appearance but remain the same substance. For example, salt dissolved in water becomes saltwater but the salt is still there and the water is still there. They have not become something else.

Solvent The solvent does the dissolving: Water dissolves many substances so we call it the universal solvent. When alcohol is used as the solvent, the resulting solution is called a tincture.

Solute The solute is what dissolves Solvent + Solute = Solution Example: If you want to make iced tea, you need the sugar to dissolve in the water. Sugar = SOLUTE Water = SOLVENT Solvent + Solute = Solution

Making a solution The solute enters the solvent and slowly breaks into pieces. The molecules of the solvent move out of the way to make room for the solute. The solute and solvent mix until the concentration is equal throughout the solution.

Solvent + Solute = Solution Types of Solutions: Solid Solvent + Solid Solute (gold jewelry) Solid Solvent + Liquid Solute (dental filling) Solid Solvent + Gas Solute (gas mask filter)

Solvent + Solute = Solution Liquid Solvent + Solid Solute (salt water) Liquid Solvent + Liquid Solute (rubbing alcohol) Liquid Solvent + Gas Solute (soda)

Solvent + Solute = Solution Gas Solvent + Solid Solute (smoke, air freshener) Gas Solvent + Liquid Solute (fog, humidity) Gas Solvent + Gas Solute (air)

Factors Affecting Solubility The nature of the solute and solvent 200 grams of zinc chloride can dissolve in 100 grams of water but only 1 gram of lead chloride can dissolve in 100 grams of water

Factors Affecting Solubility 2. Temperature An increase in temperature increases the solubility of a solid solute.

Factors Affecting Solubility 2. Temperature For all gases, solubility decreases as the temperature rises. In summer, pond water can get very warm. Warm water holds less oxygen. If the amount of oxygen gets low enough, fish die because they can’t breath!

Factors Affecting Solubility 3. Pressure Changes in pressure have no effect on the solubility of solids and liquids. For gases, an increase in pressure increases solubility and a decrease in pressure decreases solubility.

Solubility of Gases When the cap on a bottle of soda is removed, pressure is also removed, and the dissolved gas bubbles out. Eventually the soda goes flat!

How fast dissolving occurs depends on: 1. The size of the particles: Dissolving only takes place at the surface of each particle. When the total surface area is increased, the solute dissolves more rapidly. Breaking a solute into smaller pieces increases its surface area and its rate of dissolving.

How fast dissolving occurs depends on: 2. Stirring brings fresh portions of the solvent in contact with the solute, thereby increasing the rate of solubility.

How fast dissolving occurs depends on: 3. The amount of solute already dissolved When there is little solute already in solution, dissolving takes place rapidly. As the solution approaches the point where no more can be dissolved, dissolving takes place more slowly.

How fast dissolving occurs depends on: 4. Temperature For liquids and solid, increasing the temperature increases the rate at which the solute will dissolve.

Making a supersaturated solution and creating a precipitate At 25 ⁰C, only 5 g out of 100 g dissolve upon contact. Over time, 91 g become dissolved at this temperature, and the remaining 9 g rests at the bottom. When heated, all of the substance dissolves. Very slow cooling allows all of the substance to remain dissolved even though at this temperature this should not be possible. Supersaturated solutions are unstable. Eventually, the excess solute comes out of solution and falls to the bottom as a precipitate.