Rainwater Harvesting TechXcite: Discover Engineering

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1 Rainwater Harvesting TechXcite: Discover Engineering Pratt School of Engineering Duke University 1

2 Table of Contents Table of Contents 2 Module Overview 3 TechXcite Program 4 Online Support 4 and Phone Support 4 Using this Guide 5 Activity 1: The Magic of Surface Tension 6 Activity 2: Water on the Rise and Capillary Action 11 Activity 3: Rainwater Collection System 15 Activity 4: Building a Water Filter 18 2

3 Module Overview In this TechXcite: Discover Engineering Module, youth explore rainwater collection systems by looking at how rainwater is collected, how the roof works to protect a home, and water purification systems. They will investigate surface tension, capillary action and how soil filters water. They will use this knowledge to design a roof system for a house to protect it from rainwater damage and collect the water. Finally, they will design a water filter to purify the collected water. Activity 1: Youth explore surface tension and learn where it is found in nature. Activity 2: Youth explore capillary action and learn where it is found in nature. Activity 3: Youth design and build a roof with gutters to protect a cardboard house from the elements and to collect rainwater. Activity 4: Youth design a water filter and test how effective it is in filtering a water sample. Authors (Contributors: Paul Klenk, Ph.D., Gary Ybarra, Ph.D., Rebecca Simmons Editor: Carla Burgess Copyright: Engineering K-Ph.D. Program, Pratt School of Engineering, Duke University 3

4 TechXcite Program TechXcite is a partnership between the Pratt School of Engineering at Duke University, the National 4-H Council/4-H Afterschool and North Carolina 4-H. The program is directed by Drs. Gary Ybarra (PI and Paul Klenk (Co-PI. Over the past 10 years, they have co-created the successful Techtronics afterschool engineering program at Rogers-Herr Middle School and Lowes Grove Middle School in Durham, N.C. The TechXcite: Discover Engineering curriculum is building on this work by creating engineering learning modules in seven theme areas for use in afterschool programs nationwide. Together they have created an engaging, substantive, experiential and inquiry-based curriculum in engineering, technology and applied science for 4-H-supported middle school youth in afterschool programs across the nation. We hope to encourage youth in both rural and urban settings to pursue careers in engineering and technology. This Instructor s Guide is a part of the TechXcite Pilot. If your program is interested in adopting any of the TechXcite: Discover Engineering learning modules, please contact us at techxcite@duke.edu. Online Support The TechXcite Web site ( contains additional material to help you implement this module. There are videos to guide you through facilitating the activities with students. You can download copies of the Instructor's Guide and Youth Handouts. You ll also find a list of sources for any materials you ll need. Finally, there are links to additional resources. and Phone Support If you have questions about any of the material in this curriculum, please do not hesitate to ask. The Duke team is available to support you if you have questions about implementing the modules. Please contact our staff at techxcite@duke.edu. You may also call us anytime at the phone number listed on the Contact Us page on our Web site: 4

5 Using this guide The first portion of this handbook is the Instructor s Guide for all of the activities in the module. It includes this introductory section and also the Instructor s Guide for each activity. This introduction contains general information about the TechXcite curriculum, what to expect in each activity s Instructor s guide and background on tools you will be using. The Instructor s Guide for each activity follows the same format. Below is what you can expect to find in each section. At the beginning, you will find basic information about the activity. This includes: Time Required Materials Group Size This is the suggested number of students per group. Youth Handouts These will need to be copied. Instructor Preparation This describes what you need to do before the activity and approximately how much time it will take you. Learning Objectives Vocabulary Introduction, Procedure and Activity Closure Three sections form the body of the activity: Introduction, Procedure and Activity Closure. The Introduction and Activity Closure sections are scripted. You may read these sections verbatim to students. Instructions that are not to be read to students, as well as answers to questions, are in brackets/italics. The Procedure section is not scripted. It contains step-by-step instructions for facilitating the activity with a group of students. Cleanup This section appears in activities in which cleaning up in a particular way will help reassemble the kit or prepare for the next activity. Following these instructions will keep the kit in proper order. Assessment This section tells you how to assess whether or not students understood the material presented to them in the activity. These assessments are generally based on students answers to questions asked during the Activity Closure section. 5

6 Activity 1: The Magic of Surface Tension Time Required: 45 minutes Group Size: 2 Materials List Each group needs: Penny 2 droppers 2 plastic cups 12 -long section of wax paper 2 glass slides Each class needs: Liquid dish detergent Paper towels (not provided Youth Handouts: None Instructor Preparation (5 minutes Rainwater Harvesting Determine where you will get water for the activity. Gather some paper towels for the activity. Any type will do, such as towels from the restroom dispenser. Learning Objectives After this activity, students should be able to: Explain that surface tension is caused by the attraction between molecules of a liquid. Explain that detergents are surfactants that reduce the surface tension of water and therefore have a very useful role in cleaning. Vocabulary Word Molecules Surface tension Surfactant Definition The smallest unit of a substance with uniform properties. A result of the attraction between liquid molecules. A substance that reduces the surface tension of water. Introduction In this project, you re going to learn about water and about what it means to collect and use rainwater. We call this rainwater harvesting. First we re going to explore a few of the properties of water. Then we ll look at how those properties affect building the roof of a house, collecting rainwater and ultimately using rainwater. 6

7 Today we are going to learn about surface tension. Surface tension is caused by attraction between liquid molecules. For example, in a cup of water, all the molecules of the liquid are attracted to one another, and this attraction helps hold the water together. Surface tension is the reason that rain forms into drops. As each molecule of water vapor in the atmosphere condenses into liquid, it is attracted to other nearby water molecules, forming a drop. When the drop gets large enough, it falls as rain. Have you ever seen a video of astronauts drinking a liquid in space? In space, you see that the water forms a floating sphere and does not easily break into smaller pieces. So what does surface tension do? [It holds liquid molecules together.] Another example of surface tension you may be familiar with is the way certain aquatic insects appear to walk or skate on the surface of the water. This is only possible when the force created by the weight of the bug is less than the attractive force, the surface tension, between water molecules. Can you think of any other everyday examples of surface tension? [Allow students to brainstorm and respond. If you have a board, write down students answers. Examples: Being able to overfill a cup with water, objects able to float even though they have a density higher than water, large rain droplets sliding down a car s windshield, but smaller droplets sticking to the windshield, and liquid droplets forming on nonstick pans, which ensures food does not stick.] The surface tension of water can be reduced and changed for many purposes. Substances that reduce the surface tension of water, such as cleaning solutions and detergents, are known as surfactants. Surfactants make water a more effective cleanser. For example, detergents and dish soaps reduce the strength of water molecules, allowing the water to bond with oils and dirt and essentially pull them from your clothes and dishes. Procedure 1. Place students in pairs. The same partners will work together throughout the project. 2. Remind students that they are not to drink the water in any of the activities. Part A 3. Give each pair of students a piece of wax paper and two droppers. Make sure to have paper towels to clean up as over time the water will go through the wax paper. 4. Tell students to drop several droplets of water on the wax paper and try to make two or more water droplets join together (as shown at right. Ask students why drops of 7

8 water have formed on the wax paper. [As with raindrops, the attraction between the molecules causes them to join together and form a droplet with a spherical shape.] 5. Instruct students to add a couple of droplets of detergent in a dry place on the wax paper. Tell them to place a couple of drops of water near the drops of detergent. 6. Now ask them to try to get two or more of the water droplets to join together. [To do this, they can put a little detergent on the tip of the dropper and use it to try to push two or more water droplets together. It will become harder to drag the water droplets because they lose their form when the detergent touches them.] 7. Tell students to discard the wax paper and wash their droppers. Part B 8. Give each pair of students two glass slides. 9. Give these instructions: Gently rub the slides together and notice whether you feel any resistance. Now place three drops of water on one slide and put the other slide on top. Gently rub the slides together, noting any resistance. Now try to pull the slides apart. Place two drops of water and one drop of detergent on one slide. Put the other slide on top and then gently rub the slides together. Part C 10. Hand out plastic cups and pennies. 11. Instruct the pairs of students to fill each of their plastic cups with water halfway and then add dish detergent to one of them. 12. Challenge students to see how many individual drops of plain water they can put on top of the penny using the dropper. The penny should be lying flat on the work surface, heads up. They should place the drops one at a time, counting as they go. (Note that it can be difficult to count the drops if there are too many bubbles inside the dropper. 13. Record their results on the board for later. 8

9 14. Ask students: What did you notice about the amount of water on your penny? Why do you think the water did not initially spill over the edges of the penny? [The surface of the water formed a cusp on top of the penny caused by surface tension; the attraction between the molecules in the top layer of the water was so great that it kept them from spilling over.] 15. Tell students to dry off their penny and place it back flat on their work area, heads up. 16. Now challenge students to see how many individual drops of the water/detergent mixture they can put on the top of the penny using the dropper. They should place the drops one at a time, counting as they go. Record their results on the board for later. 17. Ask students: What did you notice about the amount of water that stayed on the penny? Why do you think you were able to fit fewer drops of the water/detergent mixture on the penny? [The attraction between the water molecules was weakened when detergent was added, reducing the surface tension.] Activity Closure [Ask students the following questions and allow them time to answer aloud.] 1. Why doesn t water easily run off the top of a penny? [The attractive forces cause surface tension, holding the water molecules together on top of the penny. This is also the reason why you can overfill a cup with water without the water spilling over the cup.] 2. How did surface tension change when you added detergent to the water? [Surface tension was reduced. In the case of the wax paper experiment, water droplets did not form when detergent was added because the detergent interfered with the attraction between the water molecules.] 9

10 Detergent and cleaning solutions are an example of how chemical engineers have used a scientific concept, the surface tension of water, to design a solution that solves a problem. The problem in this case is that dishes, clothes and other items get dirty. Assessment Ask students: What is surface tension and how can you change its strength or bond? [Surface tension is the result of the attraction between liquid molecules. You can change its strength by adding surfactants, such as liquid detergent.] Have students name some common examples of surface tension. [Some examples include water bugs walking across water, raindrops forming, and being able to overfill cups with a liquid without it spilling.] 10

11 Activity 2: Water on the Rise and Capillary Action Time Required: 45 minutes Group Size: 2 Materials List Each group needs: Wooden Coffee stirrer Drinking straw Glass capillary tube Ruler Shallow plastic disposable plate Six sugar cubes Paper towels (Not included Plastic cup Each class needs: Food coloring Masking tape Youth Handouts: None Instructor Preparation (5 minutes Determine where you will get water for the activity. Gather some paper towels for the activity. Any type will do, such as towels from the restroom dispenser. Learning Objectives After this activity, students should be able to: Explain that capillary action is an adhesion force that results as a liquid and solid interface. Identify a few examples of how capillary action is used at home and in nature. Vocabulary Word Capillary action Meniscus Definition The adhesion that results from surface tension when a liquid intersects a solid surface; also, the flow of liquids through porous materials. The curve at the top surface of a liquid caused by adhesion to the walls of its container. 11

12 Introduction Today we are going to learn what capillary action is and what it does. Next time, you ll be designing a rainwater collection system and exploring ways that capillary action might affect the roof of a house. Capillary action is the adhesion that results from surface tension when a liquid intersects a solid surface. For example, in a glass beaker filled with water, the water molecules that touch the walls of the container stick to the glass. This adhesion causes the water molecules touching the wall of the beaker to move uphill against gravity, and a meniscus, or curve, forms at the surface of the water. What do you think affects how far the liquid will rise up the side of the glass? [Allow students to respond. If you have a board, write down students answers. The type of liquid and also the diameter of the container determine the height that the liquid rises to.] You can observe the effects of capillary action in your home and in nature. Paper towels rely on capillary action to wick or soak up liquids. In trees, capillary action enables water in the roots to reach the leaves in the upper branches. Capillary action also describes the flow of liquids through porous materials, so it is very important for helping water move in soil from wet areas to dry areas. Procedure Part A: Paper Towel 1. Put students back with their partners from Activity Distribute plastic cups, coffee stirrer, food coloring and paper towels. 3. Remind students that they are not to drink the water in any of the activities. 4. Have students fill their plastic cups with water, add a few drops of food coloring and stir. 5. Instruct students to fold the paper towel lengthwise several times and touch the tip of it to the water. 6. Ask students why water moves up into the paper towel, defying the force of gravity. [Capillary action causes the water to move quickly through the small pores of the paper towel.] 12

13 Part B: Sugar Cubes 7. Hand out sugar cubes and plates. Remind students not to eat any sugar cubes. 8. Tell students to build a tower of sugar cubes on the plate (see picture. The sugar cubes must be touching one another. 9. Ask students what they think would happen if they poured some water onto the plate around the sugar cubes. Then tell them to pour some of the colored water around the base of the tower and observe what happens. Ask why water moves up into the sugar cubes, defying the force of gravity. [Capillary action causes the water to move quickly upward through the small pores of the sugar cubes.] 10. Explain that with in experiments, capillary action allowed the water to move against gravity. Part C: Straws 11. Collect the plates and distribute drinking straw, glass capillary tube ruler, and marker. Students will keep the cups of colored water. 12. Have students dip their drinking straw into the water. Students should minimize any stirring motion. Remove the straw from the water and draw a line on the straw where the water level is and where the water crept up to. Repeat this step with the coffee stirrer and glass capillary tube. 13. Use the ruler to determine the water rise in each tube and record. Ask them what they think might cause differences in the height of the rise? [This could be caused by differences in the diameter of the tubes.] Did you see any liquid rise in the wooden coffee stirrer? [There was likely a small rise. Water found small pores in the wood, the same as with the sugar cubes. If the rise was imperceptible, it means there weren t enough pores in the wood.] 13

14 Activity Closure [Ask students the following questions and allow them time to answer aloud.] Rainwater Harvesting 1. What did you notice about the shape of the water surface in the tubes with water? [A meniscus, or curved surface, is formed at the top of the water due to the attraction between the water molecules and the solid tube surface.] Then ask students the following questions to connect capillary action back to the module. 2. Does anyone know how shingles on the roof of a house work to keep water off the roof? [Shingles are overlapped so that there are no gaps when water flows down the roof. If shingles overlapped the wrong way, water would flow into the gap in between shingles.] 3. How far do you think one shingle needs to overlap the next shingle on the way down the roof? [It must overlap far enough so that water cannot creep up the roof between the shingles due to capillary action.] This is important when constructing a roof. The roof on your house will last a long time (15 to 30 years if built correctly. Assessment Ask students the following questions: What is capillary action and how can you change its strength? [Capillary action is caused by surface tension when a liquid intersects a solid surface or when liquids flow through porous materials. For water in a tube, the diameter of the tube and also the type of liquid, including properties such as density and viscosity, affects the amount of capillary action. Another factor is whether there are other substances mixed in the water. Water containing detergents, for example, has less surface tension, so capillary action is reduced.] List some everyday examples of capillary action. [Paper towels absorbing liquid spills, water in trees traveling from the roots upward to its leaves, etc.] 14

15 Activity 3: Rainwater Collection System Time Required: 60 minutes Group Size: 2 Materials List Each group needs: Aluminum foil Corrugated cardboard box Additional scrap cardboard Each class needs: Tape Gentle Garden watering can with sprinkler head (Not Included Measuring cup Additional scrap material, if available (Not Included Rainwater Harvesting Youth Handouts: Rainwater Collection System Instructor Preparation: Ask each student to bring a cardboard box from home that is about 1-2 on each side. Gather some extra boxes in case any students forget. Select a location outside where students can test their box roofs. You will be pouring water on the roofs to see how their construction holds up. A site with a gradual slope can be helpful. If there is a slope, make sure to test from the uphill side of the box house. Be sure there s a convenient source of water for the watering can. Learning Objectives After this activity, students should be able to: Explain the purpose of gutters. Explain that collecting rainwater can save water usage from other sources. Explain that in many parts of the country, water is a scarce resource. Use the engineering design process to design a roof and gutter system. Vocabulary Word Definition Aquifer Large, natural underground source of water. Desalinization Process for removing salt. Drought A period of dry weather leading to water shortages and usually reduced crop yields on farms. 15

16 Introduction Where does the water that comes out of your faucet come from? [Give students a few minutes to brainstorm water sources.] It depends on where you live, but generally the water you use at home comes from rivers, lakes or aquifers, which are natural underground reservoirs. Many towns get their water from man-made lakes. What s the problem with using seawater? [It s got salt in it.] To solve this problem, engineers came up with a process to remove salt from seawater called desalination. This is used in places that have access to the ocean but not to local freshwater sources. Removing salt from water uses a lot of energy, so it is an expensive process. It s done only if other freshwater sources are not available. Outside of your home, what are some important uses of fresh water? [Irrigation and power generation are the two biggest by far. Also farming, manufacturing, firefighting, etc. These three links provide some information er.html In some areas of the world, especially in years when there is less rain than normal, water is a scarce resource. When it rains a lot less than normal, that is called a drought. Today you re going to design systems to collect the rainwater that lands on a house. Once collected, that rainwater can be used in place of water from your tap. Procedure 1. Put students back with their partners from the previous activities. 2. Tell students you will be presenting them with an engineering design challenge. Like engineers, they will be solving a problem within certain specifications and constraints. 3. Distribute handouts and go over them with the class. a. Describe the design challenge and review the specifications and constraints. b. Describe the materials they are allowed to use and show students where to find them. They may use any of the scrap cardboard, wax paper and aluminum foil available. You may have other materials you would like to offer, such as disposable utensils, straws or tape. c. Tell them that they will be testing their roofs under a sprinkle from a watering can. 16

17 d. Tell them how much time they have. This project can be done in as little as 30 minutes, but students will produce better, more creative projects if you can give them 45 minutes. e. Remind them not to drink any of the water. 4. Set up a demonstration area outside. Begin by pouring water onto an example cardboard model houses without a roof. The cardboard will be soaked, as you would expect this demonstrates the need for roofing materials that are waterproof. This also shows students how you are going to be pouring the rain onto their roofs. This demonstration should help them understand how to tailor their design. 5. To test the roofs, hold the watering can and pour, such that most of the water hits the roof. It s OK if some lands next to the house, though. You should not pour directly into the collector though. [If it rains the day you want to test the houses, just put the houses out in the rain. The collectors will catch some rain on their own, but that amount should be roughly the same for all of the houses, assuming they are all in the same place. Activity Closure [Ask students the following questions and allow them time to answer aloud.] 1. What are some things you noticed about your houses and catchment systems? 2. Which of your ideas worked well and which ones didn t? 3. Name one way you might improve your design. 4. Did you notice any examples of capillary action during this activity? [They may have noticed that the cardboard walls got wet and that water traveled along the wall via capillary action.] Finally tell students that in the United States, rainwater collectors are generally used for non-drinking uses of water, so the water does not need to be as clean. It still needs to be filtered, as they will find out in the next activity. Ask them, What are some nondrinking uses of water in the home? Examples would include water for washing clothes, showering, flushing toilets, etc. Assessment You should be able to assess how well students understand the design process from their descriptions of how they would improve their designs. Ask students to write why they think somebody would install a rainwater collection system. [To conserve water; more in-depth answers would explain that during droughts, water is less available, so saving drinking water for other uses helps society.] 17

18 Activity 4: Building a Water Filter Time Required: 45 minutes Group Size: 2 Materials List Each group needs: Scissors Two clear plastic cups Measuring cup 20-ounce soda bottle (Not Included Each class needs: Soil (Not Included Gravel (Not Included Sand (Not Included Limestone (Not Included 2-liter soda bottle (Not Included Youth Handouts Building a Water Filter Instructor Preparation: Buy bags of soil, sand and limestone/rock at a home improvement or garden supply store or find them outside. Ask students to bring in empty 20-ounce soda bottles. Obtain an empty 2-liter soda bottle. Learning Objectives After this activity, students should be able to: Design and build a water filter. Explain how a water filter works. Introduction Groundwater is filtered by soil, sand and sediment that it passes through. This filtration is so effective that water from wells is usually clean enough to be consumed without additional treatment. In cities and municipalities, water treatment plants use large filters designed to clean water taken from surface waters such as lakes and rivers. These filters, in combination with chemical treatment, make water safe for drinking and using. 18

19 Procedure 1. Put students back with their partners from the previous activities. 2. Distribute handout and materials. 3. Tell students to cut 2 to 3 inches off the bottom of their bottle with the scissors. They can discard this piece along with the bottle cap. The bottle opening will be the filter drain. 4. Place larger pieces of gravel into the bottle over the drain. 5. Have students fill the bottle chamber with soil samples that will filter the water. Let students design their own unique filter by choosing which materials to use and how to arrange them in their bottle. Each pair of students should record which materials are added, approximate quantities, and the order in which they are added to the bottle. An example might look like the picture on the right. 6. As a class, have students fill a single 2-liter bottle with dirt and water and shake the bottle well. Each pair of students should then fill a plastic cup with dirty water. Everyone s cup should be filled to the same level. 7. Instruct teams to pour the dirty water into their filter and collect the water from the filter in their other plastic cup. 8. Let students compare their clean water samples and discuss the materials and quantities they used to make their filter. They should discuss the approximate amount of time that it took for the dirty water to pass through their filter. 19

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21 Activity Closure [Ask students these questions and allow them time to answer aloud.] 1. What factors affect how clean water will be after it has been filtered? [The filtering effect depends on which materials are used to build the filter and the quantities of those materials. Materials with larger particle sizes will filter out larger contaminants in the water but not finer contaminants. For example, sand is composed of smaller particles than gravel is and therefore it will filter out smaller contaminants from the water.] 2. What factors affect how fast water will pass through a filter? [The amount of time depends on the size of the particles. Materials with smaller particle sizes will filter out smaller contaminants, but it will take longer and the filter may be clogged by the larger contaminants. This reduces the capacity of the filter and slows filtration.] Assessment Ask students these questions: How would you configure your filter to make it as efficient as possible at removing contaminants? [The materials with the largest particles should be at the top of the filter, and the materials with the smallest particles should be at the bottom, near the drain. This configuration ensures that the large contaminants are removed from the water first, and then smaller and smaller contaminants are removed as the water moves through the filter and out of the drain.] If you are designing a water filter for a water treatment plant to make water clean enough to drink, what materials might you add to your filter and how would you change it? 21

22 Youth Handouts Rainwater Harvesting Activity 3: Rainwater Collection System Engineering Design Challenge When engineers create a new design, one of their first tasks is to understand the restrictions that are imposed by the nature of the product and its purpose. For example, when they design a building, it might be necessary for it to withstand certain conditions, such as 100 mph winds. It may also need to shelter people from specific weather conditions, for example, it might be required that the building be able to maintain an indoor temperature of 70 degrees F when it is 0 degrees F outside. Specifications and restrictions are known as design constraints. Engineering Design Problem: Your instructor will give you a cardboard box that represents a house. You must put a roof over the house that will protect it from rain. In addition, you should collect as much rainwater from the roof as possible. Optimize your design within the following design constraints: 1. Water from a watering can will be used to simulate rainwater striking the roof. (If it is raining outside, you may do the experiment in the rain. 2. You must collect the rainwater runoff in a measuring cup placed at least 5 inches from the house. 3. You may use materials provided by your instructor, including tape, cardboard, aluminum foil and wax paper. You may also ask to use some extra types of materials. 4. Testing will be outside. 5. You must work within the amount of time allotted by your instructor. Be sure to spend time planning with your partner before you begin building. 1

23 Youth Handouts Rainwater Harvesting Activity 4: Building a Water Filter Engineering Design Challenge In the last activity, you collected rainwater. Now you must design a way to filter the water so that it will flow smoothly through the plumbing system in your home. Be sure to spend time planning with your partner before you begin. Design Problem: You must create a filter that can be used to remove dirt and other particles from a dirty water sample. The water should be made as clean as possible after it has gone through the filter. In addition, the water needs to move through the filter as quickly as possible. Optimize your design within the following design constraints: 1. The structure of your filter will be a plastic soda bottle with 2-3 cut off the bottom. The bottle will be turned upside down and water will flow in the top and out through the smaller end (see diagram below. 2. Put larger gravel and rocks at the bottom to hold the components of your filter in the bottle. 3. You will use the materials provided by your instructor, which may include, dirt, gravel, sand and/or limestone. You will decide how to arrange these materials in the filter. 4. To test your filter, dirty water will be poured through it. 2