Slide 1

Colligative PropertiesEquilibrium Vapor PressureWhen water is heated, it forms water vapor. This hangs over the pot like a cloud, creating pressure.

When the vapor pressure equals atmospheric pressure, the water boils.

BOILING POINT ELEVATIONBoiling point elevation is a colligative property.Doesn't depend on type of substance; only depends on amount of solutes added to the waterWhen a nonvolatile solute is added to water, it takes the water longer to get to the pressure where it will boil. The temp has a chance to rise, so the boiling point of the water is made higher.The more you add to the water, the higher the boiling point will be.FREEZING POINT DEPRESSIONFreezing point depression is a colligative property.When a nonvolatile solute is added to water, it takes the water longer to get to the pressure where it will freeze. The temp has a chance to drop, so the freezing point of the water is made lower.If the freezing point is made lower, the substance must get much colder before it can freeze. This is why PennDot uses salt on the roads in winter (and liquid calcium chloride.)

Water is used to cool down your car engine. It is contained in the radiator of your car.During winter, the water could freeze and crack the radiator. Adding antifreeze (ethylene glycol) lowers the freezing point and prevents the water from freezing.

Ice Cream2 tablespoons sugar1 cup half and half Combine in small bag teaspoon vanilla then seal and put in cup salt Place in large bagIce cubes large bag1 pint size bag1 gallon size bag