Acids, bases, and solutions Chapter 3 Section 1

Key concepts What are the characteristics of solutions, colloids, and suspensions? What happens to the particles of a solute when a solution forms? How do solutes affect the freezing point of a solvent?

Key terms Solution Solvent Solute Colloid suspension

Main idea of a solution Solution: a well-mixed mixture that contains a solvent and at least one solute Solvent: the part of a solution present in the largest amount. It dissolves the other substances. Solute: the substance that is present in a solution in a smaller amount and is dissolved by the solvent. A solution has the same properties throughout. It contains solute particle that are too small to see. Water is the universal solvent.

apply We have two liquids, A and B. There are 10 ml in liquid A There are 20 ml in liquid B Which substance is the solvent and which is the solute?

Colloids and suspensions Not all mixtures are solutions. Some are colloids or suspensions. Colloid: a mixture containing small, undissolved particles that do not settle out. Suspensions: a mixture in which particles can be seen and easily peparated by settling or filtration. This Photo by Unknown Author is licensed under CC BY-SA

compare Colloids Suspensions A colloid contains larger particles than a solution. Particles are still to small to see. Particles are large enough to scatter a beam of light. Particles will not settle. A suspension does not have the same properties throughout. Contains visible particles Particles will settle out. This Photo by Unknown Author is licensed under CC BY-SA

Particles in a solution When a solution forms, particles of the solute leave each other and become surrounded by particles of the solvent. Ionic and molecular solutes: Positive and negative ions are attracted to the polar water molecules. Sugar and water break into individual molecules. Solutes and conductivity: A solution of ionic compounds in water conduct electricity.

Effects of solutes on solvents Solutes lower the freezing point and raise the boiling point of a solvent. Lowers the freezing point: Crystals form when water freezes The solutes make it harder for water to form crystals. Higher boiling points: In liquid water, molecules are close to each other. Higher temperatures allow these molecules to move faster and escape liquid form. Solutes prevent these molecules from escaping.