Unit 4 Lesson 7 Hard Water and Soft

Unit 4 Lesson 7 Hard Water and Soft Water

BELLRINGER: Reflection Ø Briefly tell me what you saw in the experiment from yesterday.

VII. Hard Water and Soft Water A. You have probably heard the term “hard water, ” but what exactly is it? 1. Water that comes into our homes was, at one time or another, in a lake stream, or underground reservoir. a. For most people, that water goes through some sort of treatment process before it comes into their home. - The water is filtered to get rid of foreign particles. - Chlorine is usually added to kill the microscopic organisms that thrive in the water. - Most water treatment plants also add flouride to the water for good dental hygiene.

Hard Water and Soft Water b. Many people think hard water is the result of the treatment process. This is not the case. - If you get your water from a freshwater well with no treatment process at all, you are just as likely to have hard water as someone who gets their water from a water treatment plant.

Hard Water and Soft Water 2. Hard water is a result of the sources from which the water is taken. a. Some areas of the world (especially the midwestern United States) have rocks (like limestone) that are rich in certain metal ions like calcium ions. These metal ions are part of ionic compounds that make up the rock.

Hard Water and Soft Water b. What does water do to ionic compounds? - It dissolves them. Water from regions of the world that are rich in limestone and other metalcontaining rocks tends to have lots of metal ions dissolved in it. That’s what hard water is. Hard water – Water that has certain dissolved ions in it – predominately calcium and magnesium ions.

Hard Water and Soft Water B. Problems with Hard Water 1. Just like salt dissolved in water makes water taste bad, calcium ions dissolved in water also affect the taste of water. - Some people who are used to the taste of the water actually think it makes it taste better, but many people don’t like it.

Hard Water and Soft Water 2. The metal ions in hard water react with soap to make a scum. - This reduces the ability of soap to clean things. 3. Hard water tends to build up scales on pipes and fixtures. - These scales are the result of ionic compounds that become undissolved when the water changes temperature. - These scales build up in sinks, bathtubs, and toilets to make the stains referred to as “hard water stains. ” 4. Although the ionic compounds in hard water pose no health risks, most people simply would rather not have them in the water due to the concerns just mentioned.

Hard Water and Soft Water C. Many people get rid of hard water by “softening” it with a water softener. 1. In a water softener, a chemical process called “ion exchange” removes ions like calcium and magnesium from the water. a. However, the calcium and magnesium ions must be replaced with something else, usually sodium ions. b. If you have a water softener, you probably know that in order for the water softener to work, salt must be added to it.

Hard Water and Soft Water 2. Recall that salt is made up of sodium ions and chloride ions. In a water softener, the sodium ions from the salt are exchanged with the calcium and magnesium ions in the water. a. This works very well because out taste buds react differently to sodium ions that they do to calcium and magnesium ions. As a result the funny taste is removed. b. Also sodium ions do not form ionic compounds that result in scales left on pipes and fixtures. c. Finally, sodium ions do not react with soap to make scum, so you feel cleaner when showering.

Hard Water and Soft Water D. Although soft water is more pleasant than hard water, it can pose a minor health risk for some people. Sodium ions can cause heart trouble in certain people. - The amount of sodium ions you get by drinking soft water is relatively small compared to the amount of sodium ions you get from your food. Nevertheless, people who are on strict lowsodium diets should either not soften their water or use more expensive, sodium-free watersoftener salts, like potassium chloride.

BELLRINGER: Question 4. 12 Calcium and magnesium ions are both the result of atoms that lose electrons. Thus they are positively charged ions. Suppose you actually could remove calcium and magnesium ions from water without replacing them with other positive ions. If you slowly started removing only calcium and magnesium ions from the water, you would find that as time went on, removal of the ions would become more and more difficult. Eventually, it would be nearly impossible to remove any more calcium or magnesium ions in the water, even though there might still be ions left. Why?