Waterproof that Roof!
Lesson focuses on how structural engineers have improved the designs of building — specifically roofing — over the years to improve the quality of homes and life. Teams of students work together using simple materials to design a roof that will keep the contents of a plastic house dry during a water test.
- Learn about structural engineering.
- Learn about materials engineering.
- Learn how engineering can help solve society’s challenges.
- Learn about teamwork and problem solving.
Age Levels: 8-18
Build Materials (For each team)
Required Materials
- Plastic storage container or planter insert (at least 10 x 25 cm)
Optional Materials (Trading/Table of Possibilities)
- Leaves, grass, cotton balls, paper towels, string, paper clips, cardboard, tape, newspaper, wooden dowels, branches, shells, nuts, pipe cleaners, non-water proof fabric, wax, oil.
- Pieces of Foil or Plastic wrap (no larger than 4 square cm)
Testing Materials
- Large bin or sink
- 1 liter of water per team
- Measuring cup
Materials
- Large bin or sink
- 1 liter of water per team
- Measuring cup
Process
Place each of the designs one-by-one inside a bin (test outside, if weather allows). Pour 1 liter of water onto the roof. Wait 10 minutes, then remove the roof and use a measuring cup to measure the amount of water (if any) that leaked into the plastic house. Use the following scoring process.
Scoring
Use the rankings below to score each roof based on the amount of water which leaked into the plastic house:
No water = 5 points
¾ liter of water = 4 points
½ liter of water = 3 points
¾ liter of water = 2 points
1 liter of water = 1 point
Design Challenge
You are a team of engineers given the challenge of creating a waterproof roof for a small plastic house. You may use any materials provided to you and will have to devise a frame and covering that will prevent water from entering the interior. You can expect a rainstorm containing a liter of water!
Criteria
- Must build a frame and covering that can withstand a “rainstorm” consisting of 1 liter of water
Constraints
- Use only the materials provided
- Teams may trade unlimited materials
- Break class into teams of 2-3.
- Hand out the Waterproof that Roof! worksheets, as well as some sheets of paper for sketching designs.
- Discuss the topics in the Background Concepts Section.
- Review the Engineering Design Process, Design Challenge, Criteria, Constraints and Materials.
- Instruct students to start brainstorming and sketching their designs. Before students begin brainstorming ask them to consider (use the Background Concepts section as a resource):
– The different shapes and materials used in the roofs they see in your community.
– How roof shapes need to change to suit different climates, for example, a flat roof is not a good choice for an area that received a great deal of snow as the weight of snow is more likely to collapse the roof structure.
– What is the hydrophobic effect? - Provide each team with their materials.
- Explain that students must design a roof structure to protect a plastic house and its contents from a simulated rainstorm. The roof must be able to withstand a “rainstorm” of 1 liter of water. Each team should identify their “house” with a name or number.
- Announce the amount of time they have to design and build (1 hour recommended).
- Use a timer or an on-line stopwatch (count down feature) to ensure you keep on time. (www.online-stopwatch.com/full-screen-stopwatch). Give students regular “time checks” so they stay on task. If they are struggling, ask questions that will lead them to a solution quicker.
- Students meet and develop a plan for their structure. They agree on materials they will need, write/draw their plan, and present their plan to the class. Teams may trade unlimited materials with other teams to develop their ideal parts list.
- Teams build their designs.
- Test the roof designs using the 1 liter of water inside a bin or tub.
- Teams should calculate their score based on how much water leaked into the plastic house.
- As a class, discuss the student reflection questions.
- For more content on the topic, see the “Digging Deeper” section.
Student Reflection (engineering notebook)
- What aspect of the design of the package that had the best overall score do you think lead to its success?
- What was the best aspect of your design? Describe one part of your design that you think worked the best.
- If you had a chance to do this project again, what would your team have done differently?
- How do you think your roof would have held up to 10 liters of water? How about 100 liters of water?
- If you could have selected some building materials which were not made available to you, what would you have selected? Why?
- If your roof design were used on a real building, do you think it would require frequent maintenance? Why?
- Do you think your roof design might be considered “green?” Why or why not?
- Do you think this project worked better because you were part of a team, or do you think you could have done a better job working alone?
- Do you think that engineers work alone, or in a team when they are developing new materials, processes, or products?
Time Modification
The lesson can be done in as little as 1 class period for older students. However, to help students from feeling rushed and to ensure student success (especially for younger students), split the lesson into two periods giving students more time to brainstorm, test ideas and finalize their design. Conduct the testing and debrief in the next class period.
Roofing Materials
The primary job of a roof is to keep water out of a structure. These structures can range from something as simple as a bird house or mailbox to a sports stadium. Of course, roofs also protect against wind, cold, and heat, and also keep unwanted animals and pests out. The pitch (or angle) of a roof is usually proportional to the amount of precipitation the building anticipates. Houses where there is low rainfall may have flatter roofs than areas where large rain or snowfall levels are anticipated. In these areas, steeply pitched roofs with efficient gutter systems are prevalent.
History
With the involvement of engineers, much of the innovations and changes in roofing have taken place in the last 200 years, but of course roofs have been important to society for much longer. The Greeks and Romans were believed to be the first to experiment with different roofing styles. The Romans introduced slating and tiling as early as 100 BC. Thatched roofs made of woven grasses were introduced around 735 AD, and have been used extensively in many parts of the world. Thatch is roofing made of plant stalks in overlapping layers. In most of Europe and the United Kingdom, thatch was the preferred roofing material in the countryside — and also in some villages — until the late 1800s. Wooden shingles and clay tiles became more popular and spread to mass-production of roofing materials. Concrete tiles are a more recent development. Now, a variety of engineered materials are used to improve water resistance and also increase the lifespan of a roof. Thatched roofs, for example, may require frequent maintenance, while some more recent materials can last up to thirty years without maintenance. But performance isn’t the only attribute valued in a roof. Thatch roofs once looked in danger of dying out, and considered a symbol of poverty, but a thatching revival is under way as people look to these designs for their charm in spite of high maintenance.
Roofing Materials
The materials used in a roof may be determined by a variety of factors including local laws, material availability, climate, cost, and frequency of required maintenance. Materials can be just about anything, from wheat straw, sea grass, banana leaves, laminated glass, aluminum sheeting, slate, ceramic tile, cedar panels, plastic or rubber sheets, asphalt and asbestos shingles, galvanized steel, and fiberglass sheets, to precast concrete. Newly engineered materials, and advances in solar panels and sun roofs have also had an impact on what roofs look like and how they perform over time.
What is Nanotechnology?
Imagine being able to observe the motion of a red blood cell as it moves through your vein. What would it be like to observe the sodium and chlorine atoms as they get close enough to actually transfer electrons and form a salt crystal or observe the vibration of molecules as the temperature rises in a pan of water? Because of tools or ‘scopes’ that have been developed and improved over the last few decades we can observe situations like many of the examples at the start of this paragraph. This ability to observe, measure and even manipulate materials at the molecular or atomic scale is called nanotechnology or nanoscience. If we have a nano “something” we have one billionth of that something. Scientists and engineers apply the nano prefix to many “somethings” including meters (length), seconds (time), liters (volume) and grams (mass) to represent what is understandably a very small quantity. Most often nano is applied to the length scale and we measure and talk about nanometers (nm). Individual atoms are smaller than 1 nm in diameter, with it taking about 10 hydrogen atoms in a row to create a line 1 nm in length. Other atoms are larger than hydrogen but still have diameters less than a nanometer. A typical virus is about 100 nm in diameter and a bacterium is about 1000 nm head to tail. The tools that have allowed us to observe the previously invisible world of the nanoscale are the Atomic Force Microscope and the Scanning Electron Microscope.
How Big is Small?
It can be hard to visualize how small things are at the nanoscale. The following exercise can help you visualize how big small can be! Consider a bowling ball, a billiard ball, a tennis ball, a golf ball, a marble, and a pea. Think about the relative size of these items.
Scanning Electron Microscope
The scanning electron microscope is a special type of electron microscope that creates images of a sample surface by scanning it with a high energy beam of electrons in a raster scan pattern. In a raster scan, an image is cut up into a sequence of (usually horizontal) strips known as “scan lines.” The electrons interact with the atoms that make up the sample and produce signals that provide data about the surface’s shape, composition, and even whether it can conduct electricity. Many images taken with scanning electron microscopes maybe viewed at www.dartmouth.edu/~emlab/gallery
What is the Hydrophobic Effect?
Hydrophobic comes from the word hydro (water) and phobos (fear). It can be demonstrated by trying to mix oil and water. And, also is evident if you look at some leaves and flower petals that repel water in droplets after a rainstorm. For the leaves, the water repellant can sometimes be a waxy coating on the leaves, or can be the existence of tiny hairlike projections off the surface of the leaf which causes a buffer of air between the hairs — the air keeps the water away.
Superhydrophobic Surfaces
Superhydrophobic surfaces such as the leaves of the lotus plant have surfaces that are highly hydrophobic, or very difficult to wet. The contact angles of a water droplet exceeds 150° and the roll-off angle is less than 10°. This is referred to as the Lotus effect.
Fabric Applications?
Scientists and engineers who were aware of the hydrophobic effect decided to apply nanotechnology to the surfaces of fabrics to make them waterproof too! The waterproof feature often also helps protect fabrics from staining because liquid cannot easily soak into the fabric fibers. A good example is the work done by a company called Nano-Tex. The company adds nano “whiskers” to cotton fibers in the same way that some leaves have little “hairs” on their surface. Creating the effect for fabric is a little tricky — a cotton fiber is shaped like a round cylinder, and Nano-Tex adds tiny nano “whiskers” all around the cylinder so it has a fuzzy surface. The fabric doesn’t appear any different or feel any different, but it does repel liquids. And, because liquids do not soak into the fabric, the process also helps the fabric resist staining too. Nano-Tex utilizes nanotechnology to: 1) design molecules with specific performance attributes; 2) engineer the molecules to assemble on the surface of textile fibers with extreme precision, and 3) ensure that they permanently attach to the fibers through patented binding technology. If the molecules were not permanently attached then the fabric might lose its ability to push water away after several machine washings. Over 80 textile mills worldwide are using Nano-Tex treatments in products sold by more than 100 apparel and commercial interior brands. This is just one example of an industry applying nanotechnology to solve problems.
- Criteria: Conditions that the design must satisfy like its overall size, etc.
- Engineers: Inventors and problem-solvers of the world. Twenty-five major specialties are recognized in engineering (see infographic).
- Engineering Design Process: Process engineers use to solve problems.
- Engineering Habits of Mind (EHM): Six unique ways that engineers think.
- Hydrophobic Effect: It can be demonstrated by trying to mix oil and water together.
- Iteration: Test & redesign is one iteration. Repeat (multiple iterations).
- Nanotechnology: The ability to observe, measure and even manipulate materials at the molecular or atomic scale.
- Prototype: A working model of the solution to be tested.
- Scanning Electron Microscope: A special type of electron microscope that creates images of a sample surface by scanning it with a high energy beam of electrons in a raster scan pattern.
- Waterproof: Resistance to water
Internet Connections
Recommended Reading
- Nanotechnology For Dummies (ISBN: 978-0470891919)
- Nanotechnology: Understanding Small Systems (ISBN: 978-1138072688)
- Smart Guide: Roofing: Step by Step (ISBN: 978-1580114806)
- Materials for Architects and Builders (ISBN: 978-0815363385)
- Knack Treehouses: A Step-by-Step Guide to Designing & Building a Safe & Sound Structure (ISBN: 978-1599217833)
Writing Activity
Write an essay or a paragraph about how technology has improved the reliability and durability of roofs in the past ten years. Or, write an essay about green roofing techniques and their impact on the environment.
Alignment to Curriculum Frameworks
Note: Lesson plans in this series are aligned to one or more of the following sets of standards:
- U.S. Science Education Standards (http://www.nap.edu/catalog.php?record_id=4962)
- U.S. Next Generation Science Standards (http://www.nextgenscience.org/)
- International Technology Education Association’s Standards for Technological Literacy (http://www.iteea.org/TAA/PDFs/xstnd.pdf)
- U.S. National Council of Teachers of Mathematics’ Principles and Standards for School Mathematics (http://www.nctm.org/standards/content.aspx?id=16909)
- U.S. Common Core State Standards for Mathematics (http://www.corestandards.org/Math)
- Computer Science Teachers Association K-12 Computer Science Standards (http://csta.acm.org/Curriculum/sub/K12Standards.html)
National Science Education Standards Grades K-4 (ages 4-9)
CONTENT STANDARD A: Science as Inquiry
As a result of activities, all students should develop
- Abilities necessary to do scientific inquiry
- Understanding about scientific inquiry
CONTENT STANDARD B: Physical Science
As a result of the activities, all students should develop an understanding of
- Properties of objects and materials
CONTENT STANDARD D: Earth and Space Science
As a result of their activities, all students should develop an understanding of
- Properties of earth materials
CONTENT STANDARD E: Science and Technology
As a result of activities, all students should develop
- Abilities of technological design
- Understanding about science and technology
- Abilities to distinguish between natural objects and objects made by humans
CONTENT STANDARD F: Science in Personal and Social Perspectives
As a result of activities, all students should develop understanding of
- Science and technology in local challenges
CONTENT STANDARD G: History and Nature of Science
As a result of activities, all students should develop understanding of
- Science as a human endeavor
National Science Education Standards Grades 5-8 (ages 10-14)
CONTENT STANDARD A: Science as Inquiry
As a result of activities, all students should develop
- Abilities necessary to do scientific inquiry
- Understandings about scientific inquiry
CONTENT STANDARD B: Physical Science
As a result of their activities, all students should develop an understanding of
- Properties and changes of properties in matter
CONTENT STANDARD E: Science and Technology
As a result of activities in grades 5-8, all students should develop
- Abilities of technological design
- Understandings about science and technology
National Science Education Standards Grades 5-8 (ages 10-14)
CONTENT STANDARD F: Science in Personal and Social Perspectives
As a result of activities, all students should develop understanding of
- Populations, resources, and environments
- Risks and benefits
- Science and technology in society
National Science Education Standards Grades 9-12 (ages 14-18)
CONTENT STANDARD A: Science as Inquiry
As a result of activities, all students should develop
- Abilities necessary to do scientific inquiry
- Understandings about scientific inquiry
CONTENT STANDARD E: Science and Technology
As a result of activities, all students should develop
- Abilities of technological design
- Understandings about science and technology
CONTENT STANDARD F: Science in Personal and Social Perspectives
As a result of activities, all students should develop understanding of
- Personal and community health
- Science and technology in local, national, and global challenges
CONTENT STANDARD G: History and Nature of Science
As a result of activities, all students should develop understanding of
- Science as a human endeavor
- Nature of scientific knowledge
- Historical perspectives
Next Generation Science Standards Grades 2-5 (Ages 7-11)
Matter and its Interactions
Students who demonstrate understanding can:
- 2-PS1-2. Analyze data obtained from testing different materials to determine which materials have the properties that are best suited for an intended purpose.
Students who demonstrate understanding can:
- 3-ESS3-1. Make a claim about the merit of a design solution that reduces the impacts of a weather-related hazard.
Engineering Design
Students who demonstrate understanding can:
- 3-5-ETS1-1.Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.
- 3-5-ETS1-2.Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.
- 3-5-ETS1-3.Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.
Next Generation Science Standards Grades 6-8 (Ages 11-14)
Engineering Design
Students who demonstrate understanding can:
- MS-ETS1-2 Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.
- MS-ETS1-3. Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.
Standards for Technological Literacy – All Ages
The Nature of Technology
- Standard 1: Students will develop an understanding of the characteristics and scope of technology.
- Standard 2: Students will develop an understanding of the core concepts of technology.
Technology and Society
- Standard 4: Students will develop an understanding of the cultural, social, economic, and political effects of technology.
- Standard 5: Students will develop an understanding of the effects of technology on the environment.
- Standard 6: Students will develop an understanding of the role of society in the development and use of technology.
- Standard 7: Students will develop an understanding of the influence of technology on history.
Design
- Standard 8: Students will develop an understanding of the attributes of design.
- Standard 9: Students will develop an understanding of engineering design.
- Standard 10: Students will develop an understanding of the role of troubleshooting, research and development, invention and innovation, and experimentation in problem solving.
Abilities for a Technological World
- Standard 11: Students will develop abilities to apply the design process.
The Designed World
- Standard 20: Students will develop an understanding of and be able to select and use construction technologies.
Industrial Engineering
Computer EngineeringWaterproofing Challenge
You are part of a team of engineers who have been given the challenge to develop a new process for waterproofing clothing. You have been provided with several pieces of cotton along with many possible materials you might decide to use for your waterproofing technique. For the purposes of your challenge, “waterproof” means that water should not be absorbed by the fabric, but will bead up on the fabric instead. You may try two or three different solutions and see which works best!
Planning Stage
Meet as a team and discuss the problem you need to solve. Use the box below to describe your solution and list the materials you think you’ll need to meet the challenge. Explain why you think your solution will solve the problem!
|
Fabric A Your plan and hypothesis:
Materials Needed:
|
|
Fabric B Your plan and hypothesis:
Materials Needed:
|
|
Fabric C Your plan and hypothesis:
Materials Needed:
|
Manufacturing Stage
Execute each of your plans (be sure to mark each piece of fabric, so you know what process you applied to it).
Investigation Stage
If you have access to a microscope, examine each of your pieces of fabric and in the box below describe what you see, noting both what you see and how they differ from the other fabric samples. You’ll have a chance to examine a sample of fabric that has been altered at the nano level too! Consider whether the fabric surfaces appear smooth, bumpy, convex, concave, or have other characteristics.
| Surface Observations | |||
| Fabric A | Fabric B | Fabric C | Nano Fabric |
|
|
Testing Stage
Over a wash basin or sink pour water over your fabric and see if it beads up or is absorbed. If your teacher agrees, you may wish to use a colored water or juice to more easily see if the water is absorbed at all. Mark your observations below.
| Water Test Observations | |||
| Fabric A | Fabric B | Fabric C | Nano Fabric |
|
|
Evaluation Phase
Complete the following questions as a group:
1) Did any of your fabrics prove to be waterproof?If yes, which procedure do you think was the best, and why?If no, why do you think your procedures did not work?
2) What solution of another team do you think worked best? Why?
3) What do you think would happen if you washed and dried your fabric? Would it retain the waterproofing?
4) What was the most surprising observation during the microscope comparison (if you completed that part of the activitiy)?
5) How did the nano treated fabric compare to your most successful fabric in the water test?
6) How did the nano treated fabric compare to your most successful fabric under the microscope?
7) If you had to do it all over again, how would your team have approached this challenge differently? Why?
8) Do you think that materials engineers have to adapt their original ideas during product testing? Why might they?
9) Did you find that there were many different solutions in your classroom that met the project goal? What does this tell you about how engineering teams solve problems in the real world?
10) Do you think you would have been able to complete this project easier if you were working alone? Explain…
11) What other applications can you think of where a surface might be changed at the nano scale to improve function or performance? One idea is coating windshields so water flows off faster…..what can you think of?
Downloadable Student Certificate of Completion
