Water Purification: Differences in density and miscibility Water is polar. –Recall polar = having poles, + and -. Non-polar substances do not dissolve in polar ones--Like dissolves like. Non-polar and polar substances are immiscible--they do not mix. If you let a mixture of oil and water settle, they will separate. Which layer is on top? –(hint--think of salad dressing)

Water Purification: Filtration Filtrate = liquid collected after filtration Sand filter = Traps and removes larger solid impurities Charcoal = Adsorbs foreign substances in water. Adsorb = To attract and hold impurities Removes substances that cause bad taste, odor or cloudy appearance Used in fish aquariums

Percent Yield Percent yield = Remaining amount x 100% Starting amount Example: If you start with 100 ml of water and have 80 ml left after purification, what is the percent yield? Percent yield = 80 ml x 100% =.80 x 100 = 80% 100 ml

Data Analysis: Histograms

Purification: Distillation Distillation is used to separate mixtures based on differences in boiling points. Liquid with lower boiling point evaporates first. The evaporated liquid condenses as it passes through the cool condensation tube. The condensed liquid drains into the clean container below.

Properties of solutions and mixtures A solution that contains ions will conduct electricity. –Recall that an ion is an element or compound which has gained or lost electron(s). Electrical conductivity can be measured with a conductivity meter. –Any circuit that will indicate passing of electricity can serve as a qualitativie conductivity meter. The Tyndall effect is the incidence of light passing through a mixture due to particles being large enough to reflect light.

Hard Water Chemistry in the Community, by the ACS, W.H. Freeman and Co., 2002 Excess of Ca 2+, Mg 2+, and/or Fe 3+ dissolved in water results in “hard” water. In nature, as groundwater flows over limestone, chalk and other minerals containing calcium, magnesium, and iron, these ions may be dissolved Man-made pollutants may also cause hard water Hard water does not form a soapy lather easily, therefore interfering with the desired cleaning action of soap. In hard water, soap reacts with hard water ions to form insoluble compounds: Soap scum or bathtub ring