Solutions

Solutions A mixture that appears the same throughout and is mixed at the molecular level. Solutions can be liquids, gases or solids. Alloys are SOLID solutions.

Classifying Matter - Overview

In the Mix: Solute – Substance being dissolved. Solvent – Substance doing the dissolving. (Usually the larger quantity.) Water is the “universal solvent”.

How Dissolving Happens Water molecules are polar – they have a (+) end and a (-) end. Water molecules cluster around the solid molecules with their negative ends attracted to the positive ends of the solid. Water molecules and solid molecules spread out and mix evenly to form a solution.

Solubility Solvation – process of surrounding solute particles with solvent particles to form a solution The rule for dissolving solutions is “like dissolves like” Polar substances will dissolve in polar solvents Non polar substances will dissolve in non polar solvents Non polar will NOT dissolve in polar and vice versa

Increasing the Rate of Solvation Agitation (Stir, Shake) Increasing Temperature Increasing Surface Area (Crush)

Agitation Increases the speed of the particles speeds up the dissolving process when dissolving solids into liquids. Decreases the dissolving process in gases.

Increasing Temperature More collisions of particles as temperature increases.

Particle Size (Increasing Surface Area) Smaller particles dissolve faster than larger particles. more surface area Sugar cube vs. ½ teaspoon sugar (Teaspoon will dissolve faster)

Rate of Dissolving for gases Pressure (gases) – Increase in pressure causes more to dissolve. Ex: soda

Effects of temperature on solubility of a gas Increasing temperature decreases gas solubility Think of drinking a coke…what’s fizzier, a cold coke or a hot coke?

Effects of pressure on solubility of a gas Increasing pressure, increases gas solubility Think of a coke bottle…What will happen if you leave the lid off?

Solubility and Concentration Solubility – The amount of substance that can dissolve in a solvent. Concentration – Depends on the amount of substance dissolved. Concentrated – large amount of solute in solvent. Dilute – small amounts of solute in solvent.

Types of Solutions Saturated – Contains all the solute it can hold at a given temperature. Unsaturated – Able to dissolve more solute at a given temperature. Supersaturated – Contains more solute than a saturated one at the same temp. These are unstable solutions made by raising the temp of a saturated solution then adding more solute.

Other Solutions Electrolytes – Solution of ions that conduct electricity. Nonelectrolytes – Solution that forms no ions in water and cannot conduct electricity. Suspension – Solution in which solid particles are in a liquid. (Particles settle.) Colloid – Homogeneous solution – large particles, light cannot shine through.

Reading Solubility Graphs According to the graph above, about how many grams of KBr are needed to make a saturated solution in 100 g of water at 30° C? 70 grams KBr

Reading Solubility Graphs According to the graph above, what kind of solution would you have if you dissolved 10 g of KCl in 100 g of water at 0°C? Unsaturated

Some Solubility Curves How many grams of KNO3 can be dissolved in 200g of water at 50oC? 160g