Lab / experiment Grade 2 Science

Hard Ground or Grassy Ground? A Grade 2 Runoff Test

A grade 2 lab where students compare rainwater runoff collected from a foil-lined tray and a soil-filled tray to see which surface absorbs more water.

Grade: Grade 2
Subject: Science
Material: Lab / experiment
Time: 45 min
Prep: Moderate prep
Materials: 2 shallow trays or foil pans, Aluminum foil, enough to line one tray completely, Potting soil or mulch, about 2 cups, for the second tray, 2 collection cups, 1-cup measuring cup, for pouring, A measuring cup marked in fluid ounces, for measuring runoff, Paper towels, Water, about 2 cups total

Standards

K-2-ETS1-3 NGSS

Analyze data from tests of two objects designed to solve the same problem to compare the strengths and weaknesses of how each performs.

How this material aligns: Students record and compare runoff data in ounces between the foil-lined Tray A and soil-filled Tray B designs in Steps 5 through 7 and the Data & Analysis table, analyzing test data from two designs solving the same rainwater problem exactly as this standard requires.

All materials for K-2-ETS1-3 →

2.OA.A.1 Common Core Math

Use addition and subtraction within 100 to solve one- and two-step word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using drawings and equations with a symbol for the unknown number to represent the problem.

How this material aligns: Analysis questions 2 and 6 have students subtract within 100 to find how many more ounces one tray collected than the other and how many ounces did not run off, the compare and take-from word problems this standard specifies.

All materials for 2.OA.A.1 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-16.

Objectives

Students will compare runoff data from two ground-surface designs to determine which lets more rainwater soak in.
Students will measure each tray's runoff in ounces and subtract within 100 to compare the two results.

Vocabulary

Key words: runoff, soak in, surface, predict

Teacher overview

Hazel Bend's playground has one section of hard, paved ground near the entrance and one grassy section near the fence. When rain falls, which surface lets more water soak in, and which lets more of it run off? This investigation has students build two small test trays, one lined with foil to represent a hard surface and one filled with soil to represent grassy ground, then pour the same amount of water over each and compare how much runs off. The comparison mirrors the same question engineers ask when deciding how much of a real playground or parking lot to pave.

Hard Ground or Grassy Ground? A Grade 2 Runoff Test — Grade 2 Science

Name: ____________________________ Date: ______________

Procedure

Step 1. Your teacher will cut a small notch in the low end of each tray so water can pour out into the cup. Tilt each tray a little. Put a cup at the low end of each tray. The cup will catch water that runs off.

Step 2. Line Tray A with foil. Press it flat. Foil stands for a hard surface. Water cannot soak into it.

Step 3. Fill Tray B with soil. Use about 1 inch of soil. Soil stands for grassy ground. Water can soak into it. Safety note: wash your hands after you touch the soil.

Step 4. Write a prediction first. Which tray will have more runoff, A or B? Write one sentence to explain your guess.

Step 5. Pour 1 cup of water on Tray A. Pour it slowly and evenly. Wait 30 seconds. Pour the water from Tray A's cup into the measuring cup. Read the ounces. Write the number in the data table.

Step 6. Empty and dry the collection cup. Now test Tray B the same way. Pour 1 cup of water on Tray B. Wait 30 seconds. Measure the runoff. Write the number in the table.

Step 7. Compare your two numbers in the data table.

Data & Analysis

Tray	Surface type	Runoff collected (oz)
A	Foil (hard surface)
B	Soil (grassy ground)

Which tray had more runoff, A or B?
How many more ounces did Tray A collect than Tray B? Show your subtraction.
Was your guess from Step 4 correct? Use your results to explain.
Which surface lets more rain soak in: pavement or grass?
Hazel Bend wants to turn part of its paved yard into grass. Would runoff go up or down? Explain why.
You poured 8 ounces into Tray A. How many ounces did not run off? Show your subtraction.

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: Any result is acceptable as long as it matches the student's own recorded data; most groups will find that Tray A, the foil-lined tray, collects more runoff than Tray B, since foil does not let water soak in.
Answer: The difference equals Tray A's recorded amount minus Tray B's recorded amount. Accept any subtraction that correctly matches the student's own two numbers; most groups should find a positive difference of several ounces in Tray A's favor.
Answer: Answers will vary based on the student's own prediction and results; accept any response that compares the prediction to the actual data with a clear explanation.
Answer: Grass. Most groups' data should show that Tray B, the soil-filled tray, collected less runoff, meaning more of the poured water soaked into the ground instead of running off.
Answer: Down. Less rainwater would be expected to run off, because grassy ground soaks in more water than a paved surface does, based on the lower runoff amount most groups measured for Tray B.
Answer: 8 ounces (the amount poured) minus the student's own recorded Tray A runoff amount equals the ounces that did not run off; for example, if Tray A collected 7 ounces of runoff, then 8 - 7 = 1 ounce did not run off.

Differentiation

Support

Pre-build one demonstration pair of trays as a class before groups build their own, and read each step aloud while groups work.

Extension

Have students test a third tray filled with gravel instead of soil or foil, predict where its runoff amount will fall compared to Trays A and B, and explain their prediction using what they observed.

ELL supports

Provide picture cards showing each surface, foil and soil, labeled with its name, and allow students to record their runoff numbers on the data table without needing to write full sentences for every analysis question.