Visualized How Hard Is Your Water?

δ Name: ________________ Period: ____ Water Hardness: Visualized How Hard is Your Water? Hardness and salinity are two properties of water that are partially considered in determining the quality of that water. Although a water’s hardness and its salinity are measures of two different things, they refer to very similar concepts. Hardness refers to the amount of calcium, magnesium, and some other trace metal ions (metal ions that are present in relatively small amounts) in water. Calcium and magnesium are two of the three metals that are typically most abundant in water, so some definitions of water hardness only include those two elements: Calcium and magnesium. The harder any sample of water is, the more calcium and magnesium are present in that water. If a sample has very little calcium or magnesium (which can be accomplished through some filtration methods or by drawing from a water source that is naturally low in calcium and magnesium), that water is said to be soft water. Water that is hard is often referred to as hard water. Despite its name, there is nothing physically “hard” about hard water. Ca Limescale and soap scum are two indicators of hard water. Limescale is a buildup of calcium Calcium carbonate, a salt of calcium and carbonate (which is derived from carbon dioxide that has dissolved in water), that deposits on pipes and other surfaces on which hard water CaCO3 frequently comes into contact. Over time, limescale buildup can shrink the diameter of pipes Calcium Carbonate (like in the pipe pictured at the top of the worksheet). On surfaces like faucets, bathtubs, plates and drinking glasses, hard water will form white “stains” that look almost like dust. These white specks, pictured below, are calcium carbonate that has been left behind on a surface after the water that carried the calcium carbonate has evaporated. The harder any sample of water, the more salts like calcium carbonate and magnesium carbonate are dissolved in it. Soap scum is a chemical relative of limescale, and it forms when calcium or magnesium from hard water react with the chemicals in soap. Soap scum forms on surfaces where hard water and soap interact, like in sinks and bathtubs. Soap scum, like limescale, leaves white, “stain-like” deposits and can be difficult to remove from the surfaces it forms on. Hard water stains on glass Salinized soil, from water with high salinity Water’s salinity refers to the amount of sodium in that water. Sodium, along with chlorine, is one of the elements that makes up table salt. The higher the salinity of a sample of water is, the more sodium (and salt, essentially) is in that water. Salinity isn’t a problem in the same ways that hardness is a problem. Because salts that include the element sodium in them are very easy to dissolve, water with high salinity doesn’t form deposits that block off pipes like hard water does. High-salinity water does, however, taste salty, and can cause problems for agriculture. If high-salinity water is used repeatedly to water crops, the salts in that water can build up in the soil over time (shown above) and eventually make the soil inhospitable to commercial crops. Joanis - 5/26/2020 δ After reading the passage above, answer each question using full sentences. The more developed/detailed your answer, the better. If you don’t know how you would respond to a question, write about why you can’t answer it and what extra information you would need in order to develop an answer. 1. What are two indicators of hard water, and where would you expect to find them? 2. What is salinity, and what is one way it can be detected? 3. Survey your own home – look in some of the places that you suspect may show evidence of hard water, and rank them in terms of how much evidence you found. Fill in the table below with your evidence. Description of evidence Location (What do you see?) Most evidence of hard water Least evidence of hard water (but still some evidence) δ 4. What is the difference between hardness and salinity? 5. If water is not hard, it is said to be soft instead (soft water). Do you think it is possible, based on the definitions and explanations given in the passage above, that water can be both soft, and have a high salinity? Explain why or why not. 6. See how much calcium, magnesium and sodium are really in your water! In order to do this you will need: Quick Method Slow Method A saucepan/small pot A bowl (or a cup) Tap water Tap water Stovetop/hotplate A lot of free time Vinegar (optional, for cleanup) Vinegar (optional, for cleanup) For the quick method, fill up a saucepan with tap water. Then, boil all of the water off. Refill the saucepan, and boil all of the water off again. Repeat this a number of times, and you should start to see a white, chalky residue start to form around the bottom of the saucepan. This is all of the calcium, magnesium, and sodium salts that were inside the water – you can even taste it to see how salty it is. The limescale and sodium salts that were formed at the bottom of the saucepan can be cleaned up very easily by splashing it with vinegar and scrubbing. Cleanup can be done without vinegar, but it will likely take more effort and be harder to completely remove. For the slow method, fill up a bowl or cup with tap water. Then, wait for all of the water to evaporate away. Refill and repeat until limescale and sodium salts start to form. On the back of this sheet of paper, describe the appearance of the bottom of your saucepan/bowl after its contents were boiled off/evaporated for the 5th time. Describe the color, shape, texture, amount, or even the taste (you are not required to check the taste) of the residue. Also, reflect on whether you think your house has hard water or soft water. Explain your reasoning. .

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