INTRODUCTION: Water that contains calcium and magnesium ions is called "hard water" because calcium and magnesium ions can combine with other ions and compounds to leave a hard scale on the surfaces they touch. Hard water may be a troublesome in household water supplies. Fortunately, there are simple solutions to hard water problems. Hard water can be softened by the removal of metallic ions responsible for the hardness. This is known as water softening. Softened water is desirable in the bathtub, lavatory, kitchen sink, and laundry room, but is undesirable as drinking water.
This lab activity will demonstrate the different characteristics between hard and soft water. MATERIALS AND METHODS: Part I: Three test tubes labeled "A", "B", and "C" were needed. Test tube "A" was filled half way with Deionized water. Test tube "B" was half way filled with Tap water, and test tube "C" was half way filled with Hard water. A solid soap chip was added to each of these tubes and they were mixed well. Observations were recorded for each tube.
Part II: Test tubes were rinsed thoroughly, and were still labeled "A", "B", and "C." All three test tubes were filled with Tap water, and a solid soap chip was added to each tube. 4-5 drops of Calcium chloride solution were added to test tube "A." 4-5 drops of Magnesium chloride solution were added to test tube "B." Nothing was added to test tube "B", which will serve as a control. Each tube was mixed well and observations were recorded. Part III: Once again, test tubes were rinsed thoroughly and the labels "A", "B", and "C" were still visible. Test tubes "A" and "B" were filled half way with Tap water. A level plastic spatula full of Calcium sulfate was added to each tube.
2-3 drops of Soap solution was added to tube "A", and it was shaken well. A level plastic spatula of Sodium carbonate was added to test tube "B." Tube "B" was shaken and then 2-3 drops of Soap solution were added to it. The tube was shaken as before. Observations were recorded. RESULTS: In Part I, Tube "A" containing the water without any ions of calcium or magnesium formed a lot of lather at the top and the rest remained clear at the bottom.
Tube "B", containing the Tap Water and soap formed a little lather, but not as much as the deionized water. Tube "C", the hard water formed no lather at all, it formed a white scum at the top of the tube and clear water at the bottom. In Part II, when we compared Tube "C" (control), to tubes "A" and "B", we noticed the difference that the ions of Calcium and Magnesium made to the water. Tubes "A" and "B" formed immediately a big amount of white scum at the top of the tube, while the control tube, made a little lather and was a bit cloudy at the bottom. In Part III water reacted differently with other additives. Tubes "A" and "B" remained evenly cloudy with some lather at the top.
This water showed to be softened. DISCUSSION: The interaction of soap and different types of water was observed in Part I, showing the characteristics of hard and soft water. The addition of Calcium and Magnesium ions made water harder in Part II. There are various methods for water softening today.
For example the problem could be solved adding lots of soap, boiling the water, precipitating ions of Calcium and Magnesium out of the solution and replacing ions of Calcium or Magnesium with Sodium, as in Part III of the activity. A mayor reason why hard water is objectionable is because it leaves mineral deposits inside steam furnaces, hot-water heaters, hot-water pipes, and tea coffee pots. The scale formed in boilers and hot-water heaters is a poor conductor of heat and causes a waste of fuel. Household hard water problems can be solved with the installation of a water softener.
Water softeners usually consist of a tank containing an ion-exchange material such as resin beads. When water passes through, calcium and magnesium ions are exchanged for sodium ions. Further investigations will be conducted about this matter.