Chapter 7, Section 1& 2 Pages 256-267 Understanding Solutions

What is a Solution?? A solution is a uniform mixture that contains a solvent and at least one solute. Example-> A household cleaner like windex is a solution. Solvent: The part of a solution that is present in the largest amount. It dissolves the other substances. Solute: The part of the solution that is present in the smallest amount. It has been dissolved by the solvent. Figure 1, pg. 257.

Colloid A mixture that contains small, undissolved particles that do not settle out. A colloid contains larger particles than a solution but the particles are still too small to be seen easily. Example-> Milk is a colloid. Figure 2, pg. 258.

Suspension A mixture in which particles can be seen and easily separated by settling or filtration. A suspension does not have the same properties throughout. It contains visible particles that are larger than the particles in solutions or colloids. Example-> Italian salad dressing is a suspension.

Effects of Solutes on Solvents Solutes lower the freezing point and raise the boiling point of a solvent. Example->If you add salt (a solute) to water (a solvent), then try to freeze it, the temperature will have to be a lot colder (less than 0 degrees Celsius) than if you were trying to freeze pure water (freezes at zero degrees Celsius). Figures 4 & 5, pg.’s 260-261.

What happens when you add salt to boiling water? As the temperature of water rises, the water molecules get energy and escape in the form of steam. Adding salt to the water will force the water molecules to get hotter to escape, causing the water to have a higher temperature. Why does adding salt to boiling water decrease the amount of time it takes to cook food?

How is Concentration measured? To measure concentration, you compare the amount of solute, to the total amount of solution. ->[solute/solution] x 100% Example: [10g/100g] x 100%= 10% A concentrated solution has a lot of solute dissolved in a certain amount of solvent. A dilute solution has only a little solute dissolved in a certain amount of solvent.

What is Solubility? Solubility is a measure of how much solute can dissolve in a solvent at a given temperature. If more solute can dissolve, you have an unsaturated solution. If you’ve added so much solute that no more dissolves, you have a saturated solution. A supersaturated solution has more dissolved solute than is predicted by it’s solubility at a given temperature.

What factors affect the solubility of a substance? 1. Pressure: Increasing the pressure increases the solubility of gases. Opening a soda after it has been shaken will produce a spray as dissolved gas comes out of the soda solution.

What factors affect the solubility of a substance? 2. The type of Solvent: Ionic and polar compounds will dissolve in polar solvents. Like dissolves like! Nonpolar and polar compounds will not form solutions with each other! Oil and vinegar will never mix because they are polar opposites!! 3. Temperature: Solubility increases as the temperature increases. The hotter the water, the easier salt will dissolve in it.

Questions??? Complete the notes, including your summaries and questions.