Lab / experiment Grade 6 Engineering & Design

Hartsel Reservoir Evaporation Cover Design Lab

A grade 6 engineering lab where students build and test covers to slow evaporation from model reservoirs, then compare water loss to pick the best design.

Grade: Grade 6
Subject: Engineering & Design
Material: Lab / experiment
Time: 2 sessions, ~60 min total
Prep: Moderate prep
Materials: 3 identical clear cups per group, Measuring cup or graduated cylinder marked in mL, Plastic wrap, Aluminum foil or floating beads, Marker, A warm, sunny spot

Standards

MS-ETS1-2 NGSS

Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.

How this material aligns: Students compare two cover designs against a no-cover control and use the water-loss data in questions 4 and 5 to judge which design best meets the goal, the systematic evaluation this standard requires.

All materials for MS-ETS1-2 →

6.RP.A.3 Common Core Math

Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double number line diagrams, or equations, including finding a percent of a quantity and converting measurement units.

How this material aligns: Question 6 has students find what percent of its starting water the open cup lost, applying percent of a quantity to their own measured data, the ratio reasoning this standard targets.

All materials for 6.RP.A.3 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-23.

Objectives

Students will test two cover designs against a control and record water loss in milliliters.
Students will compare the water loss of each design and identify which cover slows evaporation most.

Vocabulary

Evaporation: Evaporation happens when liquid water, often warmed by the sun, turns into an invisible gas called water vapor that rises into the air. It is how water leaves oceans, lakes, and puddles.
Reservoir: A human-made lake, usually created by a dam, that stores water for later. Reservoirs supply cities and farms and help control floods.

Also: cover, control

Teacher overview

In dry summers, a town reservoir can lose a lot of water to evaporation. Engineers sometimes add floating covers to slow that loss. In this lab, students test two cover designs and an uncovered control on model reservoirs made from cups and compare how much water each one loses. The setting is the fictional town of Hartsel, whose reservoir loses water on hot days.

Students measure water loss in milliliters and use the data to pick the best cover. The lab is a simplified model, not a real reservoir, but it shows the same idea: a cover that blocks more of the open surface slows evaporation more.

Hartsel Reservoir Evaporation Cover Design Lab — Grade 6 Engineering & Design

Name: ____________________________ Date: ______________

Procedure

Label three identical clear cups A, B, and C. Pour 200 mL of water into each cup, measured with the measuring cup.
Leave cup A open with no cover. This cup is the control, the one you compare the others against.
Cover cup B fully with plastic wrap so the whole top is sealed.
Cover cup C with a floating layer of beads, or a loose foil lid that does not seal the edges.
Place all three cups in the same warm, sunny spot so they get the same heat and light.
Safety note: do not drink or taste any water in this lab. Ask an adult for help if you use a heat lamp.
After 3 days, pour each cup's water back into the measuring cup one at a time, leaving any beads or foil behind, and record the mL left in the data table.
Find the water lost for each cup by subtracting the mL left from the 200 mL you started with.

Data & Analysis

Record your measurements in the table. If your own test is not finished, use the sample data below the table to answer the questions.

Cup (cover)	Start (mL)	End (mL)	Water lost (mL)
A (no cover)	200
B (plastic wrap)	200
C (floating beads)	200

Sample data, in case your own test is incomplete: cup A ended at 150 mL, cup B ended at 190 mL, and cup C ended at 175 mL.

Using the sample data, how much water did the open cup A lose?
How much water did the fully covered cup B lose?
How much water did the bead-covered cup C lose?
Which cover slowed evaporation the most? Use the water-loss numbers to support your answer.
How many more milliliters did the open cup lose than the fully covered cup?
What percent of its starting water did the open cup lose?
A real reservoir loses water like cup A. Explain why a floating cover could help a town save water in a drought.
If you tested a third cover design, what design would you try, and why might it work better?

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

Answer Key

Answer: 50 mL. Cup A started at 200 mL and ended at 150 mL, so 200 - 150 = 50 mL lost.
Answer: 10 mL. Cup B started at 200 mL and ended at 190 mL, so 200 - 190 = 10 mL lost.
Answer: 25 mL. Cup C started at 200 mL and ended at 175 mL, so 200 - 175 = 25 mL lost.
Answer: Cup B, the plastic wrap. It lost only 10 mL, the least of the three, so the full cover slowed evaporation the most.
Answer: 40 mL. The open cup lost 50 mL and the covered cup lost 10 mL, so 50 - 10 = 40 mL more.
Answer: 25 percent. The open cup lost 50 mL of its 200 mL start, and 50 / 200 = 0.25, or 25 percent.
Answer: A cover blocks the open surface where water escapes as vapor, so less water evaporates and more stays in the reservoir. Accept any answer that links the cover to less evaporation and more stored water.
Answer: Answers vary. Accept any reasonable design, such as a full floating panel or a light-colored cover, with a clear reason tied to blocking the surface or reflecting heat.

Differentiation

Support

Pre-measure the 200 mL for each group and pre-build one demonstration set of cups so students see the setup before making their own. Provide a data table with the start column already filled and a subtraction reminder for the water-lost column.

Extension

Have groups run a second trial that also tests a light-colored cover versus a dark one at the same depth, then write a short comparison of which cover design saved the most water and whether the result was consistent across trials.

ELL supports

Provide picture cards for each cover type, labeled "no cover," "full cover," and "bead cover," and a picture of the measuring cup with a marked line. Allow students to record water loss as a number with the picture rather than a written sentence.