Do Now Explain how you would make a .75 molar solution of Na2CO3, include the actual amount of solute that will be need for this concentration of solution.

Colligative Properties of solution

Essential Question How do colligative properties of a solution differ from the properties of a pure solvent?

Colligative Properties Why do we need salt to make ice cream? Why is antifreeze added to the radiators of cars? Why is salt applied to the roads after a snow fall?

Colligative Properties Colligative properties are properties of a solution that are determined only by the number of solute particles dissolved in a fixed quantity of solvent and not by the identity of the solute particles. The four colligative properties are:- Vapor pressure Freezing point depression Boiling point elevation Osmotic pressure

Vapor Pressure Vapor pressure is the pressure of a vapor or gas over a liquid. When a solute is added to the solvent it will lower the rate of evaporation or the vapor pressure. Depends on the number of particles in the solution

Freezing Point Depression When solute particles are added to a solvent it interferes with the intermolecular forces (hydrogen bonds, London forces) that will allow a solvent to freeze at a certain temperature. When solute particles are added it lowers the freezing point because the solvent molecules cannot bond as quickly because of the interference of the solute molecules. Depends on the number of particles of the solute.

Boiling Point Elevation This is the temperature difference between the boiling point of a pure solvent and a solution, Depends on the umber of particles Particles bond to the water molecules, causing less water molecules to be available for evaporation. Temperature needs to be continually raised in order to break the solute/solvent bond in order for the solution to come to a boil.

Osmotic pressure Osmosis is the movement of a solvent through a semipermeable from the side of lower solute concentration, to the side of higher solute concentration. Osmotic pressure is the external pressure that must be applied to stop osmosis.

Do Now Name four colligative properties of a solution. Why does a solution have a lower vapor pressure than the pure solvent of that solution? Why does a solution have a depressed freezing point and an elevated boiling point compared to the pure solvent? Why does it take more kinetic energy to overcome the attractive forces of the added solute particles?