Aim: How can we describe solutions? Do Now: Take out a calculator and reference tables. If a there are 0.0934g of CO2 in 100mL of water, how many ppm are there?

Answer to the do now

Some vocabulary A solution is a homogeneous mixture (made of two or more substances). The solute is a substance that dissolves (eg. salt or sugar). The solvent is the substance that the solute is dissolved in. The solvent is usually a liquid (eg. water). If the solvent is water, the solution is said to be aqueous (aq). The amount of solute in a solution determines its concentration. More solute means more concentrated. Less solute means dilute(d).

Types of solutions (besides liquid) Alloys – Metals are mixed to form a solution. The solution becomes a solid. Example: Brass which is made of zinc and copper. Air – A solution where gases are dissolved in other gases.

Characteristics of liquid solutions Solutions are homogeneous mixtures. Solutions are clear and do not disperse light. Solutions can have color. Solutions will not settle on standing. Solutions will pass through a filter (in other words, they cannot be separated by passing through a filter).

Some More Vocabulary Solubility – how much of a substance will dissolve in a certain amount of solvent at a specific temperature. Soluble – materials with a high solubility are said to be soluble. Insoluble – materials with a low solubility are said to be insoluble.

Factors that affect solubility Polarity When an ionic substance such as salt dissolves in water, it does so because the ions that make it up are attracted to the positive and negative poles of the water. Example: NaCl

What about nonpolar substances? Nonpolar substances such as fats do not dissolve in water because there aren’t strong attractive forces between the fat and water molecules. Fat will dissolve in nonpolar solvents because the forces holding the nonpolar molecules to each other are weak. In other words, “like dissolves like”. Example: Why do we need soap to wash grease off our hands?

Factors that affect solubility 2. Temperature As temperature increases, most solids become more soluble in water. s temperature rises, solubility of gases decreases.

Factors that affect solubility 3. Pressure Pressure doesn’t really affect the solubility of solid or liquid solutes. Pressure does affect the solubility of gases in liquid solutions. As pressure increases, the solubility of gases in liquids increases. Example: A can of soda.

Factors that affect solubility 4. Surface area of a solid Solids with a larger surface area take longer to dissolve than those with a small surface area. Example: Sugar cubes v granulated sugar.

How can we tell the amount of solute a solution can hold? Reference Table G shows solubility curves for several ionic salts. The curve shows the number of grams of each substance that can be dissolved in 100g of water between 0°C and 100°C. Most lines show that solubility increases as temperature increases. The three exceptions are _____________, __________, and __________ which are all gases.

Reading the solubility curves The curve shows the maximum amount of solute that will dissolve at a specific temperature in 100g of water. This is when the solution is known to be saturated. Points below the line are known as unsaturated. Points above the line are known as supersaturated. This is a temporary condition that occurs when the solution is cooled. These solutions are unstable. The only way to make a supersaturated solution is to cool a saturated solution in which there are no crystals or impurities, such as dust, present.

Examples: How many grams of the compound KCl must be dissolved in 100g of water to make a saturated solution at 60°C? _______________ How many grams of the compound SO2 must be added to 100g of water at 20°C to make a saturated solution? ____________________ How many grams of the compound KNO3 must be added to 200g of water at 70°C to make a saturated solution? _____________________ How many grams of HCl must be added to 50g of water at 45°C to make a saturated solution? _______________________

Activity/Homework # Review Book page 123 – Copy #13-23.