 Good day! Welcome to the second lesson of JSE physical science in a series of two lessons. The topic of this lesson is hard and soft water. The objectives of this lesson are to evaluate soft and hard water in terms of the ease with which they form a leather with soap. Identify hard water as containing dissolved salts of calcium and magnesium. Describe the removal of scale from a kettle by reaction with dilute acid. Let's switch over to hear what Jason and Susie are doing. So, how was your holiday in Sumi? It was okay. It's just like I didn't like the water. You didn't like the water? That's kind of funny. Every living thing needs water. It's not a matter of choice. Yes, but it's just that the water was hard. What do you mean the water was hard? Let's go to Ms. Thompson to ask her what is the meaning of hard water. Okay, let's go. This is Thompson. Good morning, you two. Ma'am, Susie said that the water of Tume is different from our water here. The water there does not leather when you use soap and a white scum forms. Can we conduct an investigation to see why this water is different? So, we thought we could use different types of water to see whether the water samples form layer with soap or not. That is an excellent idea. Water that requires a lot of soap to leather is called hard water and water that lathers easily is called soft water. Have a seat, you two. The hardness and softness of water is caused by the presence of different ions. I think we can design an experiment so that we can taste the hardness of the different samples of water. And here we have the equipment for the experiment. We've got the test tubes, the measuring cylinder, the distilled water, tap water, the borehole water, calcium sulphate, magnesium sulphate, calcium hydrogen carbonate, magnesium hydrogen carbonate. We've got liquid soap, a spatula, a medicine dropper, and a ruler. Susie, please measure out 10 cubic centimeters of distilled water and pour it into the first test tube. And then, Jason, will you now add 10 drops of liquid soap to the test tube? Insert the rubber stopper and shake the tube 10 times. Thank you, Susie. What do you notice? Wow, it forms a layer of foam. Let me measure the layer of foam. Okay. Can you please hand me the ruler? 26 millimeters. I think we can definitely say that distilled water levels when soap is added. Does that mean that distilled water is soft? That's right, Susie. Now before we continue our investigation, I think it would be a good idea to record our results and conclusions in a table. So now that we have seen what happens when liquid soap is added to distilled water, let's follow the same process for other samples and solutions. I think you two should test these other samples too. Okay, now we're going to mix the tap water with the liquid soap. Okay, Susie. While you do that, I will get the liquid soap ready so long. After we're done with the testing, let me quickly measure the height of foam on the tap water. Okay. I'm back, you two. So I've seen you've done with the test. Shall we do the observations? Yes, ma'am. So show me what you guys have observed. Yes, ma'am. We've noticed that the height of the tap water differs to the one of distilled water because the tap water is 10 millimeters high and the distilled water is 26 millimeters high. So can we say that this tap water is also soft? That's correct. What else did you guys observe? The samples of borehole water, calcium-sourified solution, magnesium-sourified solution, calcium-hydrogen carbonate solution did not form leather but scum. And if you look closely at the surface of these samples, you can see white scum forming here. So I think these solutions are all examples of hard water. That's an excellent conclusion. Have you recorded your results in a table too? Yes, we have recorded all our results into one table. Distilled water and the sample of tap water is soft water because it forms a leather. But borehole water, calcium-sourified solution, magnesium-sourified solution and calcium-hydrogen carbonate solution are hard water because they form scum. The hardness in water is caused by dissolved calcium and magnesium ions. The scum forms because the calcium and magnesium compounds react with soap, giving an insoluble product that floats under water. If we have hard water, can we change it into soft water? What about boiling the water? You're right, Suzie. Hard water can be turned into soft water by boiling the water, but this only works in certain cases. When water changes from hard water to soft water due to boiling, we call this temporary hardness. When water does not change from hard water to soft water, when boils, we call this permanent hardness. Let's investigate what happens to this solution of calcium-hydrogen, carbonate, when I boil it. Now, Jason, would you get me the following apparatus in the storeroom? Here is the apparatus you asked for, Mrs. Thompson. Thank you, Jason. Remember when we tested this solution with liquid soap? It did not leather but formed a white scum on the surface. And so we concluded that it was hard water. Now, Suzie, I want you to heat 10 cubic centimeters of this solution till it boils. And Jason, while she is measuring, I want you to light the spirit burner. After the solution has cooled at 10 drops of dishwashing liquid, now that the solution has cooled down, Jason put 10 drops of liquid soap to it and shake it. Okay, seven, eight, nine, ten. What do you notice? Hey, look, it forms a layer of foam on the surface of the solution. So does that mean that the solution of calcium-hydrogen carbonate is an example of temporary hardness? That's right, Suzie. But remember that not all samples of hard water have temporary hardness. Some hard water samples remain hard even after boiling. For example, if we boil a solution of calcium sulfate and test it with liquid soap, no leather will form. This is an example of permanent hardness. Are there other examples of temporary and permanent hardness that we could investigate? Or does this only happen in solutions of calcium ions? That's an excellent question, Jason. Remember we said earlier, hardness in water is caused by the presence of calcium ions and magnesium ions. Yes, so does that mean that magnesium-hydrogen carbonate will be an example of temporary hard water while magnesium sulfate will be permanently hard? Yes, that's a great prediction, Suzie. Let's try it. Now, Jason, boil a sample of magnesium sulfate in a test tube. And Suzie, you boil a sample of magnesium-hydrogen carbonate. So now that the samples have cooled, you two can put in the liquid soap and see what happens. Okay, remember it should be 10 drops. Five, so far. Seven, eight, nine, ten. What do you observe? Suzie's prediction was correct. The magnesium sulfate did not form a leather but still formed a scum. The sample of water is still hard. Yes, I see that and notice that my sample of magnesium-hydrogen carbonate does form a leather. So by boiling the water, it has become soft. Does that mean that the magnesium-hydrogen carbonate has only temporary hardness? That's correct. Well done, you guys. To summarize our results, we can draw up a simple table. Calcium sulfate and magnesium sulfate solutions did not form leather after boiling, so they are permanent hard water. While the magnesium-hydrogen carbonate solution and calcium-hydrogen carbonate solution formed leather after boiling, so they are temporary hard water. I've been thinking, does that mean that a person will use more soap in areas where there's hard water when doing their washing? Yes, Jason, you will use a lot of soap in areas with hard water. Hard water has some other disadvantages as well. Scale forms inside kettles in areas where there is hard water. And notice that in the kettle at Tuma Beach, really, they don't look good. That's true, but the scale can be removed quite easily from the kettle by adding some vinegar, which is a weak acid, and boiling it. You should also know that hard water has a lot of advantages too. The calcium ions in hard water are good for bones and teeth. Some people also prefer the taste of hard water, and some brewers even believe hard water makes better beer. This was a very interesting experiment. Thank you, now I understand why the water was different in Tuma. It's been a pleasure, you two. So next time you're visiting some friends in another-