Experiment 14Hard Water and Soap （实验14硬质水和肥皂）.pdfVIP

Experiment 14-Hard Water and Soap Tap water in many parts of the country contains minerals that can interfere with the cleaning ability of detergents. Thats why water softeners are popular in these locations. Water softeners remove these minerals. In this experiment, you will make hard water from distilled water, which contains no minerals, and is therefore soft. You can then compare the sudsing ability of a detergent in soft and hard water. Hard water in the shower helps you remove soap from your skin but it causes a build up of insoluble calcium or magnesium soap scale on your shower wall that is hard and difficult to remove, thus the term HARD water. Part A-How Epson Salts (Mg2+) ions Affect the Effectiveness of Soap Materials: 10 milliliters distilled water , 2g (1 teaspoon) epsom salts (magnesium sulfate), 2 empty and cleaned screw-cap 5 mL test tubes or 5 mL test tubes with stoppers, several drops of liquid dishwashing detergent (not the kind for automatic dishwashers), several drops of liquid dishwasher soap Hypothesis: How can you tell if water is soft or hard? How does it affect cleaning? Procedure: Pour 5 milliliters (1 cup) of distilled water into each of the empty test tubes. Add 5g of epsom salts (magnesium sulfate) to one of the test tubes. Stopper or cap and shake the test tube until the epsom salts dissolve. Add a drop of liquid dish detergent to both test tubes. Seal the test tubes with their caps or stoppers. Shake both test tubes. A large amount of suds will form in the test tube without epsom salts. Far fewer suds will form in the test tube containing the epsom salts. The suds formed in this experiment are made of tiny bubbles. The bubbles are formed when air is trapped in a film of liquid. The air is trapped when it is shaken into the water. The film of liquid surrounding each bubble is a mixture of water and detergent. The molecules of detergent form a sort of framework that