hard water experiment

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Family-Style Homeschooling

Hard Water Experiment

This exploration is for all ages, as the colored smilies show. You can do the hard water experiment with your whole family together!

The hard water experiment is a chemistry experiment from Layers of Learning Unit 4-11 about the chemistry of air and water. Layers of Learning has hands-on experiments in every unit of this family-friendly curriculum. Learn more about Layers of Learning .

Hard water just means water that has minerals in it.  The minerals usually include calcium, magnesium, and others that are dissolved in the water.  You can’t usually see whether or not you have hard water just by looking at it, but you’ll probably be able to tell other ways.  One way people quickly notice is that they tend to get “ring around the tub” and other mineral deposits in their sinks and bath tubs.  You can also tell if you have hard water by how it lathers.  Water with a lot of minerals won’t bubble up as much when soap is added.  You can easily see the difference by comparing plain water with hard water that you mix yourself in this hard water experiment.

Step 1: Library Research

Before you begin experimenting, read a book or watch a video about water. Here are some suggestions, but if you can’t find these, look for books at your library or videos online about the properties of water. The colored smilies above each book or video tell you what age level they’re recommended for.

As Amazon affiliates, the recommended books and products below kick back a tiny percentage of your purchase to us. It doesn’t affect your cost and it helps us run our website. We thank you!

A Drop of Water

by Walter Wick

Properties of Water

by Amoeba Sisters

Water: A Polar Molecule

by Bozeman Science

Step 2: Hard Water Experiment

For this experiment you will need 2 plastic cups, a permanent marker, 2 straws, water (either already run through a water softener or distilled water), plaster of Paris, and dish soap.

Begin by labeling one cup “plain” and the other “hard” and then put soft or distilled water in each of the two cups.  Stir a spoonful of plaster of Paris (calcium sulfate) into the cup labeled hard.  It’s not entirely soluble, but that’s okay.  It’s fine for some to sink down to the bottom of the cup.  By adding calcium to the water you are creating your own hard water to test.

Add a few drops of dish soap into each cup and stir it in.

 Now put a straw into each cup and begin gently blowing air into the water.  Both will bubble up somewhat, but the soft water will produce more bubbles.

You can’t exactly tell from the pictures, but Tyler, with the hard water, worked much harder than Elizabeth to get his bubbles going.

The plain, soft water clearly suds more successfully.

Step 3: Show What You Know

Record the results of your experiment and write about what you’ve learned about water in your science notebook.

Additional Layers

Additional Layers are extra activities you can do or tangents you can take off on. You will find them in the sidebars of each Layers of Learning unit . They are optional, so just choose what interests you.

Fabulous Fact

Water molecules are strongly attracted to each other, also because of the positive and negative charges on opposite ends of the molecule.

This strong attraction between molecules creates surface tension and allows a paper clip to float on the surface.

Additional Layer

Most people prefer soft water for cleaning, but hard water for drinking.  In the laundry, when doing dishes, when cleaning the bathroom, and even when cleaning ourselves, soft water is best.  It works well with soap and doesn’t leave a nasty residue.  However, most people prefer the taste of hard water.  Try to drink distilled water.  You probably won’t like it.  It’s the minerals within water that make them taste good to us.  

A lot of people have favorite brands of bottled water for this reason.  You might think, “It’s just water.  It’s all the same.”  But that’s actually not true.  It’s not the actual H2O flavor that we like in the bottled water; it’s the minerals within it.  

Try doing a blind taste test of several brands of bottled water and see which you prefer.

Things like calcium, dissolve easily in water because water is polar.

The negative and positive charges on each water molecule rip other ionic molecules apart.

Water is as close to a universal solvent (something that dissolves everything) as we’re likely to find.

Think about all the ways this dissolving power of water is useful in the natural world and in our bodies. Brainstorm a list together.

Free Samples

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3 thoughts on “Hard Water Experiment”

Thanks for sharing this experiment. I’ve noticed a huge difference in the amount of soap I need in the washer after getting a softener installed.

I noticed you mentioned that many people prefer hard water for drinking. Here in OKC the hardness of the tap water makes it unbearable to drink!

I much prefer the taste of soft water from the tap, but then again I also run my drinking water through my Brita before it hits my lips so perhaps that improves the taste of the soft water.

Thanks for taking the time to read my comment 😉

I like this test

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Hardness of Water

Overview Background Pre-lab work Experimental Post-lab work

In this experiment, you will determine the “hardness” of a water sample by complexometric titration.

Learning Objectives

• Apply concepts of complexation chemistry to determine the calcium concentration of a hard water sample.

To cite this lab manual : “Hardness of Water”. A Manual of Experiments for Analytical Chemistry. Department of Chemistry at UW- Madison, Summer 2024.

Visual Abstract

Hard Water refers to water containing a considerable number of cations, which form precipitates with anions such as sulfate, carbonate, and soap. Because of its polarity and unique hydrogen-bonding properties, water is an excellent solvent. As water sits in contact with mineral solids found in other materials, such as pipes, reservoirs or simply the earth, metals such as aluminum, manganese, iron, and zinc are dissolved. The major cations involved in water hardness are Ca 2+ and Mg 2+ . These ions are universally found dissolved in water.

The Madison area struggles with the problem of water hardness. Mineral deposits are formed by ionic reactions with cations in solution resulting in the formation of insoluble precipitates. For example, when hard water is heated, Ca 2+ ions react with bicarbonate (HCO 3 ¯) ions to form insoluble calcium carbonate (CaCO 3 ). This precipitate, known as scale, coats the vessels in which water is heated, producing the mineral deposits on your dishes and in water pipes. In small quantities, these deposits are not harmful, but they may be frustrating to try to clean. More serious situations can occur in systems that boil water to produce steam. Hard water can cause deposits to build up inside pipes, eventually reducing or even blocking the flow of gas, building pressures inside the system to a dangerous level. Equally important—hard water can be blamed for bad hair days, as the soap complexes with these cations before it can get to the dirty deposits in your hair!

Hardness is numerically expressed in ppm CaCO 3 , even though other metal ions contribute to the measured hardness. This is due to tradition and to the fact that Ca is 95% the contributor. Generally, it is agreed that water containing less than 40 ppm CaCO 3 is soft and that containing more than about 150 ppm CaCO 3 is hard. Characterizing the gray area in-between depends on if you are in the business of selling water conditioners or fashionable mineral water.

The EDTA Titration

EDTA (Ethylenediaminetetraacetic acid) and its sodium salts is a complexing agent used to quantitatively determine metal ions in the first two columns of the periodic table. The procedure is faster and more convenient than by gravimetric analysis, and results are typically more precise than spectroscopic or electrochemical techniques. However, instrumental methods tend to be more sensitive in detecting concentrations of specific metals present, as well as detecting low concentrations of cations. Thus, the titration procedure described in this lab, is limited to non-specific analysis of metals at fairly high concentrations.

EDTA can exist in both acidic and basic forms, depending on the pH of the system. Figure 1 shows the structure of EDTA and the six active sites of the compound. We use the basic form Y 4- for the complexation reaction. For this reason, the experiment is carried out at a basic pH. Choosing the appropriate pH can be tricky business, however, since at basic pH, some anions are forced out of solution by precipitation. You will explore this further in the prelaboratory exercises.

You will use calmagite indicator solution to detect the endpoint of the titration. Calmagite is an a,a’-dihydroxyazo dye and exists as a wine-red color in complexed form with calcium and magnesium ions at a pH of around 10.

Notice in the procedure that a small amount of Mg-EDTA solution is added to the titration sample. This is done to sharpen the endpoint of the titration. Calmagite is a wine-red color when it is bound to metal cations. At the beginning of the titration, the sample (with only a small amount of EDTA added with the Mg cations) contains only free Ca 2+ and metal complexed calmagite. As the titration progresses both Ca 2+ and Mg 2+ become captured by the EDTA added to solution. Once all free metal cations are bound, EDTA begins to compete with the metals bound to the calmagite indicator. The formation constant for Ca-Indicator is very weak ( K f =4.4 × 10 3 ) and as a result the color change observed with only Ca 2+ in solution is very small. However, the Mg-indicator formation constant is much stronger, with K f reported to be around 5 × 10 5 . The final color change to a beautiful sky blue, with no hint of red or purple, is a result of the following reaction:

This reaction provides a sharp change of color. At the endpoint, calmagite is hydrolyzed:

The hydrolysis reaction occurs rapidly, so visually observing the intermediate clear color is not possible. Thus, the endpoint is detected colorometrically by the change from wine-red to clear blue. Adding a small amount of Na 2 MgY ensures a sharp endpoint for this titration.

Lab Concept Video

Write down your observations or notes from the video in your lab notebook.

Pre-lab Work

Review these lab skills videos prior to lab.

Key Takeaways

• Accurate and precise measurements are necessary to quantify the ‘hardness’ of water in this lab!

Extra Resources:

• Finding Property Data

Prelaboratory Exercises

• You must prepare 0.01 M EDTA titrant at least one laboratory period beforehand. EDTA is slow to dissolve but eventually does so after a few hours. Calculate the amount of dihydrated disodium salt of EDTA (MW = 372.24 g/mol) needed to prepare 1 L of titrant.
• You will have to standardize the EDTA titrant by preparing a standard calcium solution. Analyzed reagent grade powdered CaCO 3 is a good primary standard. It is also extremely hydrophilic and must be dried for 1-1.5 hours at 110 °C. Dried CaCO 3 can be stored in your desiccator. You are asked in the procedure to weigh out 1.000 g of CaCO 3 and dilute to a total volume of 1.000 L. What is the concentration of this solution? Report the answer in molarity.
• Write out the titration reactions for this experiment. What is the ratio of analyte/titrant?
• While performing the lab, your lab mate notices a systematic decrease in the amount of EDTA to reach the endpoint of the titration with CaCO 3 . Find a data table of those results below. Propose one reason why this may be happening and how to avoid it. Consider this: EDTA is a heavy molecule and acts slightly hydrophobic in solution. Its slow solubility is why you’re asked to make to EDTA standardizing solution the day before. A good explanation will consider the qualities mentioned, as well as the structure of EDTA in explaining why the solution of EDTA seems to change over the course of the experiment.

Before You Take The Quiz on Canvas

• Understand chelation and how EDTA reacts with metal cations.
• Understand the displacement titration technique, including how and why it is used in the experiment.
• Understand how EDTA is standardized using calcium carbonate.
• Be able to calculate the precise concentration of EDTA from a set of titration data—mass of calcium carbonate and the volume required to reach the end point.
• Be able to calculate the hardness of water from a set of raw data—precise concentration of EDTA and the volume required to reach the end point.

Experimental

• Prepare 1 L of 0.01 M standard EDTA titrant. Dissolve an accurately measured amount of the EDTA salt in DI water and mix well in a 1 L plastic (polyethylene) bottle. Because the titrant extracts hardness-producing cations from soft-glass containers, EDTA solution should not be stored in glass. This step should be done well before you’re ready to perform the experiment, since EDTA is slow to dissolve. You will standardize this solution against CaCO 3 , prepared in step 2.
• Prepare a standard calcium solution. Use reagent grade, dried CaCO 3 . Weigh 1.000 g of the anhydrous calcium carbonate into a beaker or weighing dish. Do not attempt to transfer the dry reagent directly into the flask. Instead, slurry it first with about 5 mL of deionized water and transfer it with the help of the wash bottle and a funnel set into the neck of a 500 mL Erlenmeyer flask. Do not use excessive amounts of water for the transfer; otherwise, the CaCO 3 will not dissolve rapidly. Add 6 M HCl, a little at a time, until the CaCO 3 has dissolved. Do not use more than 10 mL. Add 200 mL deionized water and air sparge for a few minutes to expel CO 2 . Add a few drops of methyl red indicator and adjust to the intermediate orange color by adding 3 M NH 4 OH or 1 M HCl, as required. Transfer quantitatively to a 1000 mL volumetric flask and fill to the mark with deionized water. This standard solution is equivalent to 1.00 mg /1.00 mL. PRO TIP : You’re adding a base (NH 4 OH) that is half as concentrated as the acid used to dissolve the solid. The point of this step is to get the standard CaCO 3 solution to a neutral pH. This way the buffer will be more impactful at holding the pH at 10 while you titrate. Expect you will use double the volume of HCl added. Add HCl using the principle “as much as necessary but as little as possible” will help with neutralizing the acid in the second step.
• Pipet 25 mL of standard calcium solution into a 250 mL Erlenmeyer flask.
• Add 1 to 2 mL buffer solution. (This is used to set the pH of the mixture to 10. 0 to 10.1.)
• Add 10 drops of Mg (II) – EDTA reagent.
• Add 1 to 2 drops of the calmagite indicator.
• Perform your titrations by adding the standard EDTA titrant slowly, with continuous stirring, until the last reddish tinge disappears from the solution, adding the last few drops at 3 to 5 second intervals. At the end point, the solution is a crisp blue with no hue of wine red or purple. Daylight or a daylight fluorescent lamp is highly recommended; ordinary incandescent lights tend to produce a reddish tinge in the blue at the end point. Do not extend duration of titration beyond 5 min, measured from the time of the buffer addition. The absence of a sharp color change at the endpoint of the titration usually means that an inhibitor must be added at this point in the procedure, or that the indicator has deteriorated. Make sure you do three titrations; specify the indicator.
• Determine the hardness of an unknown sample. Give your laboratory instructor a clean 10 oz. plastic bottle properly labelled with your name and section number. When you receive your water sample, quantitatively transfer to a 250 mL volumetric flask and dilute to the mark with deionized water. Mix thoroughly. Pipet a 50 mL aliquot of unknown sample into a 250 mL Erlenmeyer flask and titrate as in Step 3.  Adjust the procedure accordingly. Titrate two more 50 mL aliquots and calculate the “hardness” in ppm (mg/L) of CaCO 3 . Make sure you do three titrations.

Post-Lab Work Up

Results/Calculations

Fill out the answer sheet for this experiment completely. Use the answer sheet as a cover sheet to your notebook pages. This lab has an “accuracy” component of 10 points, thus pay attention to mixing all your solutions thoroughly, and check each other’s buret readings in lab to ensure you’re reading the burets correctly.

Challenge Questions

Challenge questions are designed to make you think deeper about the concepts you learned in this lab. There may be multiple answers to these questions. Any honest effort at answering the questions will be rewarded.

• A few drops of a Mg-EDTA reagent are used in this experiment to sharpen the endpoint. Suppose you were working with a lab partner, who misread the instructions to the experiment and accidentally pipetted 10 mL of this reagent to the solution. Must you start over with a new sample? If you must start over, explain what sort of error (systematic or random) you believe will be introduced to the measurement based on the mistake and what shift, if any, might result in the measured hardness of water of the sample.

Lab Report Submission Details

Submit your lab report on Canvas as 1 combined PDF file.  This submission should include:

• The completed answer sheet .
• Your lab notebook pages associated with this lab, which should include answers to the post-lab questions and challenge questions.

The grading rubric can be found on Canvas.

References :

• Yappert, M. C., DuPre,’ D. B., J. Chem. Ed. , 1997 74 p. 1422-142
• Harris, D. C. & Lucy, C. A. Quantitative Chemical Analysis, 10 th ed.; W. H. Freeman: New York, NY, 2020

UW Madison Manual of Experiments for Analytical Chemistry Copyright © by Chem 327/329 Team. All Rights Reserved.

37 Water Science Experiments: Fun & Easy

We’ve curated a diverse selection of water related science experiments suitable for all ages, covering topics such as density, surface tension, water purification, and much more.

These hands-on, educational activities will not only deepen your understanding of water’s remarkable properties but also ignite a passion for scientific inquiry.

So, grab your lab coat and let’s dive into the fascinating world of water-based science experiments!

Water Science Experiments

1. walking water science experiment.

This experiment is a simple yet fascinating science experiment that involves observing the capillary action of water. Children can learn a lot from this experiment about the characteristics of water and the capillary action phenomenon. It is also a great approach to promote scientific curiosity and enthusiasm.

Learn more: Walking Water Science Experiment

2. Water Filtration Experiment

A water filtering experiment explains how to purify contaminated water using economical supplies. The experiment’s goal is to educate people about the procedure of water filtration, which is crucial in clearing water of impurities and contaminants so that it is safe to drink.

Learn more: Water Filtration Experiment

3. Water Cycle in a Bag

The water cycle in a bag experiment became to be an enjoyable and useful instructional exercise that helps students understand this idea. Participants in the experiment can observe the many water cycle processes by building a model of the water cycle within a Ziplock bag.

4. Cloud in a Jar

The rain cloud in a jar experiment is a popular instructional project that explains the water cycle and precipitation creation. This experiment is best done as a water experiment since it includes monitoring and understanding how water changes state from a gas (water vapor) to a liquid (rain) and back to a gas.

Learn more: Cloud in a Jar

5. The Rising Water

The rising water using a candle experiment is a wonderful way to teach both adults and children the fundamentals of physics while also giving them an exciting look at the properties of gases and how they interact with liquids.

6. Leak Proof Bag Science Experiment

In the experiment, a plastic bag will be filled with water, and after that, pencils will be inserted through the bag without causing it to leak.

The experiments explain how the plastic bag’s polymer chains stretch and form a barrier that keeps water from dripping through the holes the pencils have produced.

Learn more: Leak Proof Bag Science Experiment

7. Keep Paper Dry Under Water Science Experiment

The experiment is an enjoyable way for demonstrating air pressure and surface tension for both adults and children. It’s an entertaining and engaging technique to increase scientific curiosity and learn about scientific fundamentals.

Learn more: Keep Paper Dry Under Water Science Experiment

8. Frozen Water Science Experiment

The Frozen Water Science Experiment is a fun and engaging project that teaches about the qualities of water and how it behaves when frozen.

You can gain a better knowledge of the science behind the freezing process and investigate how different variables can affect the outcome by carrying out this experiment.

9. Make Ice Stalagmites

10. Bending of Light

A fascinating scientific activity that explores visual principles and how light behaves in different surfaces is the “bending of light” water experiment. This experiment has applications in physics, engineering, and technology in addition to being a fun and interesting method to learn about the characteristics of light.

11. Salt on a Stick

This experiment is an excellent way to catch interest, engage in practical learning, and gain a deeper understanding of the characteristics of water and how they relate to other substances. So the “Salt on Stick” water experiment is definitely worth trying if you’re looking for a fun and educational activity to try!

Learn More: Water Cycle Experiment Salt and Stick

12. Separating Mixture by Evaporation

This method has practical applications in fields like water processing and is employed in a wide range of scientific disciplines, from chemistry to environmental science.

You will better understand the principles determining the behavior of mixtures and the scientific procedures used to separate them by performing this experiment at home.

13. Dancing Spaghetti

Have you ever heard of the dancing spaghetti experiment? It’s a fascinating science experiment that combines simple materials to create a mesmerizing visual display.

The dancing spaghetti experiment is not only entertaining, but it also helps you understand the scientific concepts of chemical reactions, gas production, and acidity levels.

14. Magic Color Changing Potion

The magic color-changing potion experiment with water, vinegar, and baking soda must be tried since it’s an easy home-based scientific experiment that’s entertaining and educational.

This experiment is an excellent way to teach kids about chemical reactions and the characteristics of acids and bases while providing them an interesting and satisfying activity.

15. Traveling Water Experiment

In this experiment, you will use simple objects like straws or strings to make a path for water to pass between two or more containers.

Learn more: Rookie Parenting

16. Dry Erase and Water “Floating Ink” Experiment

The dry-erase and water “floating ink” experiment offers an interesting look at the characteristics of liquids and the laws of buoyancy while also being a great method to educate kids and adults to the fundamentals of science.

Learn more: Dry Erase and Water Floating Ink Experiment

17. Underwater Candle

In this experiment, we will investigate a connection between fire and water and learn about the remarkable factors of an underwater candle.

18. Static Electricity and Water

19. Tornado in a Glass

This captivating experiment will demonstrate how the forces of air and water can combine to create a miniature vortex, resembling a tornado.

Learn more: Tornado in a Glass

20. Make Underwater Magic Sand

Be ready to build a captivating underwater world with the magic sand experiment. This experiment will examine the fascinating characteristics of hydrophobic sand, sometimes referred to as magic sand.

21. Candy Science Experiment

Get ready to taste the rainbow and learn about the science behind it with the Skittles and water experiment! In this fun and colorful experiment, we will explore the concept of solubility and observe how it affects the diffusion of color.

Density Experiments

Density experiments are a useful and instructive approach to learn about the characteristics of matter and the fundamentals of science, and they can serve as a starting point for further exploration into the fascinating world of science.

Density experiments may be carried out with simple materials that can be found in most homes.

This experiment can be a great hands-on learning experience for kids and science lovers of all ages.

22. Super Cool Lava Lamp Experiment

The awesome lava lamp experiment is an entertaining and educational activity that illustrates the concepts of density and chemical reactions. With the help of common household items, this experiment involves making a handmade lava lamp.

Learn more: Lava Lamp Science Experiment

23. Denser Than you Think

Welcome to the fascinating world of density science! The amount of matter in a particular space or volume is known as density, and it is a fundamental concept in science that can be seen everywhere around us.

Understanding density can help us figure out why some objects float while others sink in water, or why certain compounds do not mix.

24. Egg Salt and Water

Learn about the characteristics of water, including its density and buoyancy, and how the addition of salt affects these characteristics through performing this experiment.

25. Hot Water and Cold-Water Density

In this experiment, hot and cold water are put into a container to see how they react to one other’s temperatures and how they interact.

Sound and Water Experiments

Have you ever wondered how sound travels through different mediums? Take a look at these interesting sound and water experiments and learn how sounds and water can affect each other.

26. Home Made Water Xylophone

You can do this simple scientific experiment at home using a few inexpensive ingredients to create a handmade water xylophone.

The experiment demonstrates the science of sound and vibration and demonstrates how changing water concentrations can result in a range of tones and pitches.

Learn more: Home Made Water Xylophone

27. Create Water Forms Using Sound!

A remarkable experiment that exhibits the ability of sound waves to influence and impact the physical world around us is the creation of water formations using sound.

In this experiment, sound waves are used to generate patterns and shapes, resulting in amazing, intricate designs that are fascinating to observe.

28. Sound Makes Water Come Alive 

These experiments consist of using sound waves to create water vibrations, which can result in a variety of dynamic and captivating phenomena.

29. Water Whistle

The water whistle experiment includes blowing air through a straw that is submerged in water to produce a whistle.

This experiment is an excellent way to learn about the characteristics of sound waves and how water can affect them.

Water Surface Tension Experiments

You can observe the effects of surface tension on the behavior of liquids by conducting a surface tension experiment.

By trying these experiments, you can gain a better understanding of the properties of liquids and their behavior and how surface tension affects their behavior.

30. Floating Paperclip

In this experiment, you will put a paper clip on the top of the water and observe it float because of the water’s surface tension.

31. Water Glass Surface Tension

Have you ever noticed how, on some surfaces, water drops may form perfect spheres? The surface tension, which is a characteristic of water and the cohesive force that holds a liquid’s molecules together at its surface, is to blame for this.

32. Camphor Powered Boat

The camphor-powered boat experiment is a fun and fascinating way to explore the principles of chemistry, physics, and fluid mechanics. In this experiment, a miniature boat is used to travel across the water’s surface using camphor tablets.

33. Pepper and Soap Experiment

The pepper in a cloud experiment is a simple and interesting activity that explains the concept of surface tension. This experiment includes adding pepper to a bowl of water and then pouring soap to the mixture, causing the pepper to move away from the soap.

Learn more: Pepper and Soap Experiment

Boiling Water Experiments

Experiments with boiling water are an engaging and informative way to learn about physics, chemistry, and water’s characteristics.

These investigations, which include examining how water behaves when it changes temperature and pressure, can shed light on a variety of scientific phenomena.

It’s important to take the proper safety measures when performing experiments with hot water. Boiling water can produce steam and hot particles that are dangerous to inhale in and can result in severe burns if it comes into contact with skin.

34. Make It Rain

This experiment can be accomplished using basic supplies that can be found in most homes, make it an excellent opportunity for hands-on learning for both kids and science lovers.

Learn more: Make it Rain

35. Fire Water Balloons

Learning about the fundamentals of thermodynamics, the behavior of gases, and the effects of heat on objects are all made possible by this experiment.

36. Boil Water with Ice

The Boiling Water with Ice experiment is an engaging and beneficial approach to learn about temperature and the behavior of water. It can also serve as an introduction for further discovery into the wonderful world of science.

37. Boil Water in a Paper Cup

The “boil water in a cup” experiment is an easier but powerful approach to illustrate the idea of heat transmission by conduction. This experiment is often used in science classes to teach students about thermal conductivity and the physics of heat transfer.

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Water hardness

Meta Description

Learning Objectives

To get familiar with the different classifications of water.

To be able to understand the role of soap in distinguishing hard from soft water.

To understand how water hardness can be removed.

A powder of magnesium sulfate

Water has a relatively high amount of minerals, mainly magnesium and calcium carbonates which make it difficult for lather to form.

A chalky hard white substance mainly of calcium carbonate (CaCO3)

Permanent hardness

The hardness that will not be removed by boiling. Consist of chlorides, nitrate and sulfates of calcium and magnesium.

Temporary hardness

Hard water that is easily turned into soft water by boiling. It consists of dissolved magnesium and calcium ions.

Water that has no calcium or magnesium salts dissolved.

Fill the bottles with equal amounts of distilled water.

To one of the bottles add 2 teaspoons of Epsom salts. Seal the bottle with the cap and shake vigorously for a few seconds.

Remove the cap from the bottle and add a few drops of dishwashing detergent to each bottle.

Seal both bottles with their caps and shake them both vigorously for a few seconds.

Place both bottles on the table and observe what happens.

Try different amounts of Epsom salts in each bottle and see how that affects the amount of lather produced.

Try leaving the bottles of Epsom salts to settle for different times before adding the soap and shaking, do you see any difference in the amount of lather produced?

Ensure the caps are on tightly before you shake the bottles

Avoid touching your face while doing this experiment, if you get soap in your eye, wash face with lukewarm clean water.

Have you ever been on holiday or a different area and drank a glass of water, to notice that it tastes different to what you are used to? This might be due to the minerals which are dissolved in the water, as a result of the geology and rocks that the water had passed through during the water cycle, also known as “Hard water”. You decide to try and make a cup of tea with the water, and you slowly notice that some grey crust is developing inside of the kettle. This is the dissolved minerals in the water leaving solution and settling on the kettle. But is there a way to determine if the water is hard or soft without tasting it?

What is the difference between soft and hard water? Hard water has minerals such as magnesium and calcium ions while soft water does not.

Name the two types of water hardness. Temporary and permanent hardness

What is the difference between temporary and permanent water? One consists of dissolved calcium/magnesium hydrogen carbonate and one of calcium/magnesium sulfate respectively.

How to remove temporary hardness? By boiling the water to form a layer of limescale.

How to remove permanent hardness? By ion exchange resin

How is soap helpful in distinguishing between the two? Soap form lather in soft water and a cloudy solution in hard water.

Have you ever noticed that sometimes lather does not seem to form when you are cleaning with soap?

This is because of the hardness characteristic of water, the difference between hard and soft water is determined by the amount of mineral content dissolved within the water, mainly calcium and magnesium. When present in water, these minerals combine with soap and prevent any lather from forming. Therefore, soap only lathers in hard water once it has reacted with all of the calcium and magnesium ions, in other words, when the water becomes soft.

To distinguish between hard and soft water, the lack of lather formation from detergent can be a quick and easy test.

After the experiment, the difference between the two bottles should be very clear. The bottle which had the Epsom salts was added to it will have less bubbles compared to the bottle without Epsom salts.

Hard water is produced when magnesium or calcium ions are dissolved in the water. Initially the water is distilled, meaning that the water is pure and would have no additional solutes present, however, when you add Epsom salt and shake the water, you are dissolving magnesium ions into the water. These magnesium ions react with the detergent added to form lime soaps or soap scum which is insoluble. Lime soaps will prevent lather from forming and also is not useful in the washing process. This means that hard water requires a larger amount of soap to form any lather. In addition to this, the use of hard water can also reduce the effectiveness of appliances that use water, due to the formation of scale. Soft water does not contain magnesium or calcium in any significant amounts that would hinder the function of the detergent. http://www.water-research.net/index.php/water-treatment/tools/hard-water-hardness

M2+ + 2C17H35COONa (sodium stearate/ soap) ==== (C17H35COO)2 M (soap scum) + 2Na+

Where M is either Mg or Ca

There are two types of water hardness, temporary and permanent hardness. Temporary hardness happens when the water has dissolved bicarbonate minerals as calcium hydrogen carbonate Ca(HCO3)2 and magnesium hydrogen carbonate Mg(HCO3)2, which can be removed by the addition of washing soda or simply by boiling to form limescale (CaCO3).

Permanent hardness has dissolved calcium sulfate in the water and is relatively more difficult to remove. Boiling the water will not be enough, instead, an ion exchange resin is needed to reduce this type of water hardness. Ion-exchange resin consists of sodium ions that exchange their place with the calcium ions present in the hard water. The resin has to be charged over a period of time.

http://www.bbc.co.uk/schools/gcsebitesize/science/triple_ocr_gateway/chemistry_out_there/hardness_of_water/revision/1/

Applications

Water is an essential resource that obviously has a wide range of applications, in domestic, industrial, and even agricultural function. However, hard water can be problematic in the industry as it increases the chance of breakdowns in boilers and cooling towers. https://en.wikipedia.org/wiki/Hard_water It is important to monitor water hardness used in industrial processes, as low calcium levels in water can result in cause corrosion of metal equipment, which would eventually need to be resurfaced. On the other hand, high calcium levels result in limescale to build up in pipes and plumbing, which can cause blockages. http://www.lamotte.com/en/blog/test-factors/75-measuring-water-hardness

Water treatment technologies focus on removing undesired contaminants from water, such as metal and minerals. Bioremediation technology is a developing process in which the contaminants are eliminated in an eco-friendly manner by biological catalyzes, like fungi. The organisms bind with the metal ions and eliminate them from the water. In such studies, the influence of pH, calcium concentration, and the temperature was investigated to determine the optimum conditions for toxic metals removal by three different fungal species. http://oaji.net/articles/2017/2154-1489116400.pdf

Try it with different types of water as rainwater, tap water, and seawater, and see if there is a difference in the number of bubbles produced.

Boil some tap water and compare the hardness between boiled and unboiled tap water. Boiled water should have some of its hardness removed hence form more lather than unboiled tap water.

Add more Epsom salt and notice the difference. The more one adds the fewer bubbles are formed.

Preparation: 2 mins

Conducting: 5 mins

Clean Up: 2 mins

Number of People

1 participant

2 empty plastic bottles with caps Epsom salts Dish washing liquid Distilled water

Contributors

Chemistry for engineers page 83 by Dr. B.K. Ambasta

To Test for Water Hardness, Soap Test

Hard vs Soft Water Soap Test

Hard & Soft Water | Environmental Chemistry | Chemistry | FuseSchool

Learn How To Turn Hard Water Into Soft Water | Environmental Chemistry | Chemistry | FuseSchool

IonExchange

Additional Content

Hard water  (Beginner)

Hard & Soft Water | Environmental Chemistry | Chemistry | FuseSchool  (Intermediate)

Water Softening  (Advanced)

Cite this Experiment

Spiteri, C., & Styles, C. (2020, September 17). Water hardness. Retrieved from http://steamexperiments.com/experiment/water-hardness/

First published: September 17, 2020 Last modified: September 17, 2020

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• Experiments

Water hardness

Find out the difference between permanent and temporary hardness of water

• Calcium chloride
• Sodium hydrogen carbonate
• Put on protective gloves and eyewear.
• Conduct the experiment on the tray.
• Place the stove on the cork hot pot stand. Do not touch the stove after the experiment - wait until it cools down.
• Remove protective gloves before lighting the candle.
• Do not allow chemicals to come into contact with the eyes or mouth.
• Keep young children, animals and those not wearing eye protection away from the experimental area.
• Store this experimental set out of reach of children under 12 years of age.
• Clean all equipment after use.
• Make sure that all containers are fully closed and properly stored after use.
• Ensure that all empty containers are disposed of properly.
• Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
• Do not replace foodstuffs in original container. Dispose of immediately.
• In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
• If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
• In case of inhalation: Remove person to fresh air.
• In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
• In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
• In case of injury always seek medical advice.
• The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
• This experimental set is for use only by children over 12 years.
• Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
• The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
• The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
• Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

Solution in the flask doesn’t get cloudy after step 6..

Probably, the solution in the flask hasn’t yet heated up enough. Wait for 5 min. longer.

Step-by-step instructions

• Pour water into a flask up to a "40" mark.
• Add there all the 0.2M calcium chloride CaCl 2 solution from a vial.
• Take a fuel tablet stove and place a candle onto it. Remove protective gloves and light the candle. Set a flame diffuser onto the stove, as shown.
• Put the flask onto the flame diffuser. Wait 15 min.
• Pour all the 0.3M sodium hydrocarbonate NaHCO 3 solution from a vial.
• Water in the flask will turn cloudy.

Dispose of solid waste together with household garbage. Pour solutions down the sink. Wash off with excess of water.

Scientific description

What is water hardness.

Water hardness is a value that reflects the amount of dissolved calcium, magnesium, and iron salts in water. There is temporary hardness (that can be removed) and permanent hardness. Temporary hardness is caused by calcium and magnesium bicarbonates (Ca(HCO 3 ) 2 and Mg(HCO 3 ) 2 ), and permanent harness – by their sulfates ((CaSO 4 and MgSO 4 ) and chlorides (CaCl 2 and MgCl 2 ).

Thus, hard water is water that contains a lot of calcium, magnesium, and iron salts simultaneously.

What happens upon water heating?

When we heat water, fairly soluble calcium bicarbonate turns into poorly soluble carbonate:

Ca(HCO 3 ) 2 → CaCO 3 ↓ + CO 2 ↑ + H 2 O

White coating observed on the bottom and walls of the flask is calcium carbonate.

How to soften water?

Water containing low amounts of calcium and magnesium salts is called soft. And the process of removing water hardness is softening.

The easiest way to soften water, as it is demonstrated in our experiment, is boiling. Upon heating, calcium and magnesium bicarbonates (Ca(HCO 3 ) 2 and Mg(HCO 3 ) 2 ) undergo thermal decomposition:

Mg(HCO 3 ) 2 → MgCO 3 + CO 2 ↑ + H 2 O

MgCO 3 + H 2 O → Mg(OH) 2 ↓ + CO 2 ↑

Boiling (thermal softening) is the most ancient method to soften water for domestic needs. Of course, this process only removes temporary (carbonate) hardness. Permanent hardness persists, as we can observe in the first part of our experiment: water saturated with calcium chloride CaCl 2 leaves no precipitate upon boiling.

Distillation is closely connected with boiling. During distillation, evaporated liquid is consequently condensed on a cooled surface and, thus, is collected in form of drops. Water purified via such process is called distilled water and doesn’t contain any metal ions. Because of low mineralization, distilled water is not suitable for drinking, as it “washes out” minerals from the body. However, distilled water is widely used in science and industry.

Below you may find more information about modern methods for water softening.

Obviously, boiling is one of the easiest ways to soften water. However, such process has significant disadvantages – namely, low efficiency and high energy consumption.

Another way to soften water is to use reagents. They transfer magnesium and calcium ions into insoluble form by adding certain chemical substances – for example, calcium hydroxide Ca(OH) 2 (the process is called lime softening):

Ca(OH) 2 + Ca(HCO 3 ) 2 → 2CaCO 3 ↓ + 2H 2 O

Mg(HCO 3 ) 2 + 2Ca(OH) 2 → Mg(OH) 2 ↓ + 2CaCO 3 + 2H 2 O

Similarly to boiling, lime softening only removes carbonate hardness. In order to remove permanent (non-carbonate) hardness, deeper water softening is necessary, so in addition to slaked lime, they use sodium carbonate Na 2 CO 3 :

Ca 2+ + Na 2 CO 3 → CaCO 3 ↓ + 2Na +

Mg 2+ + Na 2 CO 3 → MgCO 3 ↓ + 2Na +

MgCO 3 + Ca(OH) 2 → Mg(OH) 2 ↓ + CaCO 3 ↓

For an even more effective removal of calcium and magnesium ions from water, they use “big guns” – sodium phosphate Na 3 PO 4 :

3Ca 2+ + 2Na 3 PO 4 → Ca 3 (PO 4 ) 2 ↓ + 6Na +

3Mg 2+ + 2Na 3 PO 4 → Mg 3 (PO 4 ) 2 ↓ + 6Na +

A drawback of this water softening method is the necessity to dose the reagents very precisely.

In industry, the most widely used technique for water softening involves ion-exchange resins . Water is passed through a special filter that withholds calcium Ca 2+ , magnesium Mg 2+ , iron Fe 2+ , and manganese Mn 2+ ions. These “caught” ions are replaced with potassium K + , sodium Na + or hydrogen H + ions released into a solution.

This method is very efficient for water softening. Advantages of this technique are low cost of reagents and absence of complex procedures, such as sedimentation and removal of a precipitate. By the way, this method is exactly how water is softened in a dishwasher. For filter to last longer, they pour salt NaCl in a dishwasher, so that it replaces calcium and magnesium in there and saturates the filter with sodium ions.

In a laboratory, they often use another water treatment process called reverse osmosis. Besides, this method is sometimes even used in homes. Water is passed through a membrane that doesn’t let metal salts go through. Importantly, reverse osmosis can only accept water that has already been preliminarily treated. A membrane is very thin and delicate: it may be damaged with high concentrations of salts. Reverse osmosis is a very expensive water treatment process, but in turn, it is relatively fast and convenient.

That’s interesting!

Which water is better for you: hard or soft.

The answer is simple: everything is good in moderation. An ideal option for everyday household use is medium hard water that contains some amount of calcium, magnesium, iron, and manganese salts. The right balance is always the way to harmony.

First of all, let’s find out why it is a problem when water is too hard. Consuming hard tap water on a regular basis may contribute to formation of kidney and bladder stones. There are no other medically proven potential hazards to human health from drinking it. Using hard water for bathing or face washing may often cause skin irritation, especially in children. Further speaking, hard water may cause some inconvenience in household activities: calcium and magnesium salts responsible for water hardness can form insoluble compounds with fatty acids contained in soap. Not only it increases soap consumption — in some regions, due to water hardness, up to 35 % of soap is spent to soften water, and then only 65 % is used for hygienic purposes. Sadly, it also leads to precipitation of insoluble calcium and magnesium salts (stearates) in sewer lines, thus, settling there soap scum. Today, most detergents, unlike regular soap, contain synthetic additives that do not react with hardness salts. Hence, nowadays the “soap problem” of hard water is passing away. Unfortunately, another problem arose: in hard water, laundry machines and dishwashers heating elements gradually deposit a layer of limescale and eventually stop working because of that. In a household, hard water causes some inconvenience, but on an industrial scale, it can create a real trouble. Even a millimeter-thick layer of limescale deposited on inside of equipment dramatically lowers its heat exchange efficiency. Not only it increases consumption of electricity for a process itself, but it can also damage the equipment. Imagine a huge kettle that consistently grows a thick layer of limescale on the bottom. Sooner or later, it will fail! And in industry, they use setups and instruments much more sophisticated than a kettle. Thus, both heating and cooling systems require careful consideration of supplied water.

Processes involving chemicals also demand thorough water treatment. For instance, textile dying is only possible with the use of extra soft water because some dyes may form insoluble compounds with calcium, magnesium, manganese, and iron ions. With hard water, that process with certain dyes could be very complicated.

Now, let’s consider advantages and drawbacks of using soft water.

Consuming soft water on a regular basis may cause issues with teeth and bones, as with drinking water we usually receive a considerable amount of necessary minerals. Luckily, the problem isn’t that huge, since the need in calcium, magnesium, and manganese consumption may be satisfied with healthy nutrition.

In soft water, soap foams much more effectively than in hard water. However, it takes considerably more soft water to rinse off a detergent than it does with hard water.

Moreover, water piping suffers from extra soft water: upon heating, water with low concentration of salts may gradually dissolve metal constructions. In chemical industry, they often use water that is more than just softened — it is distilled. Not only distilled water is very soft — it is also free of numerous impurities that do not at all affect water hardness, such as sulfates (SO 4 ) 2- , chlorides Cl - , and sodium Na + and potassium K + ions.

Distilled water: can’t get any softer

Distilled water is water that has been purified via a complex process called distillation. Distilled water contains almost no impurities. Interestingly, distilled water can be overcooled below the freezing point or overheated above the boiling point! Distilled water is normally used in chemical laboratories and in chemical industry where purity of prepared solutions is very critical. Besides that, distilled water is employed in food processing (to create certain drinks), in automotive industry (to prepare electrolyte for batteries), in medicine and color printing.

There is also water that has been purified via distillation twice — so-called double-distilled, or bidistilled, water. In composition, it is very close to chemically pure water. Is there a method to obtain water of even higher purity? Producing such water requires use of gamma-radiation followed by bubbling with inert gas — argon Ar.

Indeed, regular water contains many impurities invisible to the eye: salts, dust particles, minerals, and organic compounds. A complete opposite of regular water would be chemically pure water that contains only water H 2 O molecules.

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Experiment Total Water Hardness Experiments​

Total water hardness.

Experiment #14 from Water Quality with Vernier

Introduction

When water passes through or over deposits such as limestone, the levels of Ca 2+ , Mg 2+ , and HCO 3 – ions present in the water can greatly increase and cause the water to be classified as hard water. This term results from the fact that calcium and magnesium ions in water combine with soap molecules, making it “hard” to get suds. In Test 13, Calcium and Water Hardness , an Ion-Selective Electrode was used to determine calcium hardness, in mg/L as CaCO 3 . In this test, total hardness will be determined. Total hardness is defined as the sum of calcium and magnesium hardness, in mg/L as CaCO 3 . In addition to total hardness, the test described here will allow you to determine the concentration of Mg 2+ , in mg/L.

High levels of hard-water ions such as Ca 2+ and Mg 2+ can cause scaly deposits in plumbing, appliances, and boilers. These two ions also combine chemically with soap molecules, resulting in decreased cleansing action. The American Water Works Association indicates that ideal quality water should not contain more than 80 mg/L of total hardness as CaCO 3 . High levels of total hardness are not considered a health concern. On the contrary, calcium is an important component of cell walls of aquatic plants, and of the bones or shells of aquatic organisms. Magnesium is an essential nutrient for plants, and is a component of chlorophyll.

• Determine the total water hardness in a stream or lake.

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This experiment is #14 of Water Quality with Vernier . The experiment in the book includes student instructions as well as instructor information for set up, helpful hints, and sample graphs and data.