Date: November 4, 1999

Grade Level(s): 3

Subject(s):

• Science/Environmental Education

Description: Using a conceptual change model, students will make a connection between soil erosion by water and the effects it has on the rain forests.

Goals: Students will identify the relationship between soil erosion by water and the destruction of the rain forests.

NSES content standards: Science as inquiry; physical science: erosion

Objectives: Students will:

1. observe that soil erosion occurs when the water washes the soil away from the trays.
2. record their data.
3. construct a general scientific understanding that plants hold soil in place via roots and help prevent soil erosion by water.
4. conclude that soil erosion by water increases with the destruction of the rain forests.

Materials:

• bins (containing soil; water; graduated cylinders; 5 trays: 1 tray with grass growing in soil, 2 with just soil, 2 empty; ruler; paper towels; rubber bands)
• text book by Churchill, E., Loeschnig, L., and Mandell, M. (1998). 365 More Simple Science Experiments with Everyday Materials
• Rain Forest journals
• overhead projector
• markers and pencils

Instructional Method:

Divide class into groups of 4. Students will be given the question : Which container (the container with grass and soil or the container with just soil) will displace the greatest amount of soil when the same amount of water is poured on to each one. Students will first individually hypothesis what container will displace the greatest amount of soil and why. Students will then perform the experiment. They will determine whether the soil displaced is high, medium, or low. Students will respond to the following questions in their journals: What happens when soil erosion occurs by water?

Scientific Explanation:

The central scientific question to be answered by students is: What occurs when rain falls on to soil that contains no plants? Why does this happen? Soil erosion occurs when unprotected soil is washed away by rainfall. Plants prevent soil erosion by stabilizing the soil with their root systems.

Focus Phase:

The students will draw and describe in their journals what they think will happen when we pour a cup of water on a tray of soil with plants and a tray of soil without plants. Then the students will share their hypothesis with their groups and then the class. We will chart the hypothesis on board. This will be called “our best thinking so far.”

Challenge Phase:

Tray A will have the soil w/ the grass and Tray B will have the tray w/ only soil.
Tilt both trays with their science books so that one end is higher than the other.
Both trays need to be tilted the same.
Next, stretch a paper towel around the tops of the empty containers.
To hold paper towels in place secure them with rubber bands.
These will filter the water from the dirt as it is displaced.
Set the filter at the bottom of the container holding the grass and just the soil.
Students must KEEP ALL WATER, DIRT, AND MUD INSIDE THE BIN.
Pour water into Tray A .
After water has filtered out and just left the dirt on the paper towel have the students draw what they see using labels.
Do the same with Tray B .
The students will answer the following questions in their journals.
Which tray displaced the most soil? Why do you think this happened?
Students will also record their information on a data table provided by the teacher using the following categories.

Amount of Soil Displacement

A high level of soil displacement will be represented by a handful of soil.
A medium level will be half a handful of soil and low levels will be represented by a pinch of soil.

Concept Introduction:

Refocus students by asking what is the term used to describe what just happened with the soil?
Erosion. How does erosion occur?
The water pushes the unstable soil.
Soil erosion occurs when unprotected soil is washed away by rainfall.
Why was there less soil eroded from the container with the grass?
Plants prevent soil erosion by stabilizing the soil with their root systems.
The roots grab a hold of the soil. As a class, we will write a general scientific understanding.

Concept Application:

First have the students hypothesis what they think will happen when we do the problem below and why.
Problem: Build a hill made out of soil and then pour a cup of water on it and write in our journals of what happened. Also in our journals we will respond to the following by using our scientific understanding of erosion: Imagine this is a hill in the rain forest. What is a way to prevent a land slide from occurring?

Assessment:

In students’ journals they will develop a hypothesis of what would happen to the land and the animals of the rain forest when the trees are cut down and destroyed? Why? The students will have time to share their ideas with the class.