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Lesson plan Grade 6 Engineering & Design

Aridell Fog Catcher Water Harvest Design Lesson

A grade 6 engineering lesson where students size and compare fog-catcher mesh designs for a dry village, using area and unit rates to predict daily water harvest.

Objectives

  1. Students will calculate the water a fog catcher harvests using mesh area and a yield rate.
  2. Students will compare two fog-catcher designs and justify a choice using the numbers.

Vocabulary

Condensation
Condensation is when water vapor in the air cools down and turns back into tiny liquid water droplets. It is how clouds form and why a cold glass gets wet on the outside on a warm day.

Also: fog catcher, yield, square meter

Teacher overview

Some dry places get little rain but plenty of fog rolling in from the coast. A fog catcher is a tall panel of fine mesh. When fog drifts through the mesh, the tiny water droplets stick, join together, and drip down into a gutter and a tank. This lesson uses that idea to turn area and unit-rate math into a real water-supply design for a fictional dry village.

Students size a mesh panel, predict its daily harvest, and compare two mesh designs. A common misconception is that a taller panel always collects more water no matter what. The lesson keeps the yield rate per square meter separate from the total area, so students see that both the size of the panel and the mesh quality matter.

Procedure

Hook (5 min): Show a photo or sketch of fog moving past a screen door with drops forming on it. Ask students where the water comes from if it is not raining. Guide them to name fog as tiny water droplets already in the air.

Water cycle and condensation (10 min): Connect the fog catcher to the water cycle. Fog forms when water vapor cools and condenses into droplets. On the mesh, those droplets meet a surface, join, and grow heavy enough to drip. Name this step condensation and collection.

Model area and yield (8 min): Using a sample panel different from the handout, model the two-step method. First find area: a 3-meter by 3-meter panel has an area of 9 square meters. Then apply a yield rate: at 2 liters per square meter, that panel harvests 9 times 2, or 18 liters, on a foggy day. This is teacher modeling, not a handout answer.

Student handout work (18 min): In pairs, students complete the Aridell handout. They find panel area, scale it to daily and yearly harvest, size the design to a target, and compare two mesh designs. Circulate and confirm pairs multiply area by the yield rate rather than adding them.

Design comparison and share (6 min): Two pairs present which mesh design they would recommend for Aridell and why. The class checks that each choice names the yield per square meter that supports it.

Exit ticket (3 min): Students answer one question on a card: "Explain in one sentence what happens on the mesh that turns fog into water you can collect." Collect and scan before dismissal.

Aridell Fog Catcher Water Harvest Design Lesson — Grade 6 Engineering & Design
Name: ____________________________ Date: ______________

Student Handout

Use these facts about the village of Aridell, a fictional dry village. A fog catcher's mesh harvests 3 liters of water for each square meter of mesh on a foggy day. Aridell has about 100 foggy days each year.

  1. A mesh panel is 2 meters wide and 4 meters tall. What is its area in square meters?
  2. At 3 liters per square meter on a foggy day, how much water does the 8-square-meter panel harvest in one foggy day?
  3. Over 100 foggy days, how much water does one panel harvest?
  4. A family needs 15 liters of drinking water per day. How many days would 2,400 liters last that family?
  5. The village wants 720 liters on a foggy day. Each 8-square-meter panel harvests 24 liters that day. How many panels are needed?
  6. Design A mesh harvests 3 liters per square meter. Design B harvests 4 liters per square meter. On an 8-square-meter panel, how many more liters does Design B harvest on a foggy day?
  7. Write the two unit rates from problem 6 and name which design harvests more water per square meter.
  8. Fog is made of tiny water droplets in the air. Explain what happens at the mesh that turns fog into liquid water the village can collect.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key

Handout questions are keyed 1 to 8 in order.

  1. Answer: 8 square meters. Area = 2 meters x 4 meters = 8 square meters.
  2. Answer: 24 liters. 8 square meters x 3 liters per square meter = 24 liters.
  3. Answer: 2,400 liters. 24 liters per foggy day x 100 foggy days = 2,400 liters.
  4. Answer: 160 days. 2,400 liters / 15 liters per day = 160 days.
  5. Answer: 30 panels. 720 liters / 24 liters per panel = 30 panels.
  6. Answer: 8 liters. Design B harvests 8 x 4 = 32 liters; Design A harvests 8 x 3 = 24 liters; 32 - 24 = 8 liters more.
  7. Answer: Design B. Design A is 3 liters per square meter and Design B is 4 liters per square meter, so Design B harvests more per square meter.
  8. Answer: The droplets stick to the mesh and join. Fog droplets hit the mesh, stick, and join into larger drops that grow heavy and drip down into the gutter and tank.

Differentiation

Support

Give students grid paper so they can draw the panel and count square meters before multiplying. Provide the two-step reminder on a card: first find area, then multiply by the yield rate. Allow a calculator for the larger products in questions 3 and 5.

Extension

Ask students to design a panel that harvests at least 600 liters on a foggy day using Design A mesh. They must choose panel dimensions, show the area and harvest math, and explain one reason a village might still prefer many small panels over one large one.

ELL supports

Pre-teach "fog," "mesh," and "yield" with a labeled sketch of a fog catcher showing the mesh, gutter, and tank. Provide a sentence frame for question 8: "Fog turns into water on the mesh because ___."