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Alkalinity Protocol W Elcome Purpose Scientific Inquiry Abilities to Measure the Alkalinity of a Water Sample Use a Chemical Test Kit to Measure Alkalinity

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Alkalinity Protocol W Elcome Purpose Scientific Inquiry Abilities to Measure the Alkalinity of a Water Sample Use a Chemical Test Kit to Measure Alkalinity Alkalinity Protocol W elcome Purpose Scientific Inquiry Abilities To measure the alkalinity of a water sample Use a chemical test kit to measure alkalinity. Identify answerable questions. Overview Design and conduct scientific Students will use an alkalinity kit to measure the investigations. alkalinity in the water at their hydrology site. The Use appropriate mathematics to analyze exact procedure depends on the instructions in data. Develop descriptions and explanations the alkalinity kit used. Intr using evidence. Student Outcomes Recognize and analyze alternative oduction Students will learn to, explanations. - use an alkalinity kit; Communicate procedures and - examine reasons for changes in the explanations. alkalinity of a water body; Time - explain the difference between pH and 15 minutes alkalinity; Quality Control Procedure: 20 minutes - communicate project results with other GLOBE schools; Level - collaborate with other GLOBE schools Middle and Secondary Pr (within your country or other countries); otocols and Frequency - share observations by submitting data Weekly to the GLOBE archive. Quality Control Procedure: twice a year Science Concepts Materials and Tools Earth and Space Science Alkalinity test kit Earth materials are solid rocks, soils, water Hydrology Investigation Data Sheet and the atmosphere. Making the Baking Soda Alkalinity L Water is a solvent. Standard Lab Guide (optional) A earning Each element moves among different Alkalinity Protocol Field Guide reservoirs (biosphere, lithosphere, Distilled water in wash bottle atmosphere, hydrosphere). Latex gloves Physical Sciences Safety goggles ctivities Objects have observable properties. For Quality Control Procedure, the above plus: Life Sciences - Alkalinity standard Organisms can only survive in - Hydrology Investigation Quality environments where their needs are Control Procedure Data Sheet met. - Quality Control Procedure for Alkalinity Earth has many different environments Lab Guide that support different combinations of A ppendix organisms. Preparation Suggested activities: Practicing Your Protocols: Humans can change natural environments. Alkalinity (e-guide only) All organisms must be able to obtain and use resources while living in a Prerequisites constantly changing environment. Discussion of safety procedures when using chemical test kits GLOBE® 2005 Alkalinity Protocol - 1 Hydrology Alkalinity Protocol – Teacher Support Introduction Advance Preparation Alkalinity and pH are properties of water that are The Practicing Your Protocols: Alkalinity Learning related, but different. Alkalinity is the measure Activity, will help students understand the variables of the pH buffering capacity of the water. pH, on that may affect their measurements. the other hand, is the acidity of water. (refer to pH Protocol). pH is a very important water quality Perform the Quality Control Procedure if it has not parameter. Many plants and animals have very been done within six months. specific pH requirements and are harmed by sudden pH changes or extreme pH values. What Measurement Procedures happens to the pH of your water if acid is added? These kits are based on the technique of adding a The answer depends on how much alkalinity is in pH sensitive color indicator to the sample and then the water and how much acid is added. adding an acid titrant solution drop by drop until a color change is observed. Alkalinity is expressed as the amount of calcium There are a number of techniques the students carbonate (CaCO3) in your water, although other substances can contribute to alkalinity as well. The should follow to take quality data. units of alkalinity are either part per million (ppm) 1. Have the students read the directions or mg/L. These units are equivalent, as 1 ppm = before they begin to make sure they 1 mg/L. understand the procedure. Let us say your water has a high alkalinity. 2. Measure carefully. Read the volume of the When acid is added to the water, the alkalinity sample in the sample bottle at eye level neutralizes the acid. Some of the alkalinity will Read at the bottom of the meniscus. be used up, so that alkalinity will go down. If 3. If using a titrator, make sure that the more acid is added, the alkalinity will continue titrator is being read correctly. Most kits to decrease. Eventually, when the alkalinity is include instructions for the proper use low enough, adding acid will cause the pH to of titrators. Make sure the students are decrease. familiar with the units on the titrator. 4. If the alkalinity kit uses drops, hold the When water has high alkalinity, we say that dropper bottle vertically so that all of the it is well buffered. It resists a decrease in pH drops are the same size. when acidic water, such as rain or snowmelt, enters it. Alkalinity comes from dissolved rocks, 5. During the Quality Control Procedure and actual water testing, be sure to note particularly limestone (CaCO3), and soils. It is added to the water naturally as water comes in the color change that gives the correct contact with rocks and soil. Water dissolves the alkalinity. In many kits, it is an intermediate color change that gives the correct alkalinity CaCO3, carrying it into streams and lakes. Lakes and streams in areas rich in limestone bedrock and not the final color. For kits with an will tend to have a higher alkalinity than those intermediate color (such as a LaMotte kit), in regions with non-carbonate bedrock. if you are not sure when the intermediate color change occurs, read the titrator or If water has an alkalinity below about 100 mg/L write down the number of drops when as CaCO3, it is poorly buffered and pH sensitive. A you think it might be first occurring. For big rainfall or snowmelt event could add enough kits with only one color change during acid to lower the pH in a sensitive system. This titration, add one more drop to see if the could be harmful to the plants and animals that color changes further. If it does not, use the live there, particularly at certain times of the year previous number you wrote down. (e.g., when fish or insect larvae are hatching). GLOBE® 2005 Alkalinity Protocol - 2 Hydrology Quality Control Procedure Alkalinity Kit Precisions W For the Quality Control Procedure, you may Different alkalinity test kits have different elcome make your own baking soda standard (Making precisions. Below are values for the maximum the Baking Soda Alkalinity Standard Lab Guide). acceptable differences for some common test Alternatively, you may purchase a ready-made kits. alkalinity standard solution. Please make sure to note which standard you are using in the Hydrology Quality Control Procedure Data Sheet. LaMotte ± 8 mg/L The alkalinity of the baking soda standard is Hach ± 6.8 mg/L approximately 84 mg/L. It is the sum of the true (Low Range, 0–10 mg/L) Intr alkalinity of the baking soda added (70 mg/L) ± 17 mg/L oduction plus the alkalinity of the distilled water used (High Range, 0-50 mg/L) (usually 14 mg/L or less): 70 mg/L + 14 mg/L = 84 mg/L. If your alkalinity test kit is not listed in the table The purity of distilled water available worldwide above and you are not certain how to determine varies significantly. As a result, its alkalinity is the precision of your kit, please contact your also variable. Unfortunately, most alkalinity GLOBE Country Coordinator or the GLOBE Help test kits are not capable of producing accurate Desk and provide them with the manufacturer measurements for samples of very low alkalinities and model of your kit. (i.e., less than 30 mg/L). As a result, it is very Pr difficult to determine the actual alkalinity of your Safety Precautions otocols distilled water and therefore the alkalinity of • Students should wear gloves when your baking soda standard solution. To account handling chemicals and water that may for this, the actual measurement of your baking contain potentially harmful substances. soda standard should be 84 mg/L ±10 mg/L. If • Students should wear goggles when the alkalinity of your baking soda standard is working with chemicals. measured to be less than 74 mg/L or greater • Local authorities should be consulted on than 94 mg/L, prepare a new standard making the proper disposal of used chemicals. L sure your weights and dilutions are accurate. If A earning you are still off by more than ±10 mg/L, you may Supporting Protocols need to replace the reagents of your test kit. pH: Alkalinity is directly related to pH; waters with higher alkalinity are more resistant to changes Ready-made alkalinity standards have a precisely in pH from the influx of acid. It is, therefore, known alkalinity. During the Quality Control important to collect accurate pH data to compare ctivities Procedure, your resultant measurement should with your alkalinity data. be the actual alkalinity of your standard plus or minus the maximum acceptable difference for Atmosphere: Atmosphere measurements, especially your test kit. precipitation and temperature, are also important for interpreting your alkalinity data. Heavy rain or snowmelt, resulting in an influx of large amounts of freshwater to the system, may decrease your A water’s alkalinity. ppendix In addition, knowing the geology and soil types of your area may be important for interpreting your alkalinity data. GLOBE® 2005 Alkalinity Protocol - 3 Hydrology Helpful Hints • If your students are using multiple kits, mark the items in each kit with a dot of the same color. Use a different color for each kit. This will help avoid kit contamination by exchanging chemicals or titrators between kits. Instrument Maintenance 1. The alkalinity kit should be kept in a dry place away from direct heat. 2. All chemicals should be kept tightly capped. 3. Chemicals in the kits should last a year if they are not contaminated, and are stored in a dry area away from extreme heat.
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