I.A.3 What Happens When Water Invades Sand?

Concepts: How water is absorbed by sand, how it moves through soil and why scrub is a good water storage, recharge, and purification area.
Skills: Cooperative learning, observation, scientific method, and discussion.
Time needed: Part One: approximately 15 minutes. Part Two: approximately 15 minutes.
Best time of year: Anytime
Sunshine State Standards: LA.A.1.2.4, LA.A.2.2.5, LA.B.2.2.1, MA.A.1.2.1, MA.B.1.2.1, MA.B.1.2.2, MA.B.2.2.1, MA.B.2.2.2, MA.B.3.2.1, SC.A.1.2.1, SC.A.1.2.4, SC.C.1.2.1, SC.C.1.2.2, SC.C.2.2.3, SC.C.2.2.4, SC.D.1.2.3, SC.H.1.2.1, SC.H.1.2.2, SC.H.1.2.3, SC.H.1.2.4, SC.H.1.2.5, SC.H.2.2.1, SC.H.3.2.2, SC.H.3.2.4, SS.B.2.2.2, VA.A.1.2.2.

This two-part activity explores the strange relationship between sand and water and demonstrates the importance of drainage. During Part One, students will explore how water moves sand. During Part Two students will compare how quickly water drains through different soil types.

I.A.3 Part One—Sand Under Water

Materials:
Each team of 4 students needs:

  • Clear plastic storage container with approximately 2-3 inches (5-7 cm) of damp sand (Boxes from Part Two of the first activity can be used.)
  • Container of water (approximately 1 cup)
  • Funnel
  • Moist sponge
  • Pencil (for making burrows)
  • Waterproof marker or crayon
  • 12 dried navy beans or other small bean
Instructions for the teacher:
  1. Read The Background Scoop on Sand.

  2. Additional background information:
    When water occurs as a surface film on sand grains, it binds them together as seen in Part Two of I.A.1. When more water is added, however, the relationship changes dramatically. Once water fills all the spaces between the sand grains, the sand no longer holds together like a solid. At this point—when sand grains are in a liquid instead of having liquid sticking to them—the very wet sand begins to move like a liquid again. The sand grains actually displace some of the surrounding water, which means the sand grains are partially supported by the water (just like a person is partially supported by the water while swimming). This not only makes it tough for the sand grains to stick together, but also keeps the force of gravity that collapses burrows from being quite so strong. This is important for the animals that make burrows in the sand—as you will see.

  3. Distribute all the materials. Have each student use a pencil to make 3 vertical burrows next to one side of the box so they can see inside. Each side of the box will have three burrows. (Several replications are important in the scientific method.)

  4. Using a waterproof marker or crayon, students should initial or personalize 3 dried beans and drop one in each burrow.

  5. After students make their burrows, go around to each team’s box and gently, slowly move the box back and forth on the table two or three times to see what happens to the burrows in moist sand.

  6. Tell the students that enough water will be added to each box to cover the sand. The water will be added to the middle of the box, away from the burrows. Give the teams five minutes to discuss what they think will happen to the burrows when the box is flooded.

  7. Write each team’s hypothesis on the board or overhead projector. Explain that a hypothesis is a statement about what you think might happen. A hypothesis is used to work on an experiment and is not to show how much a person knows.

  8. Instruct students to put the moist sponge on top of the sand in the middle of the box. (The sponge prevents the water from creating a large hole in the sand when pouring out the funnel spout.) Students should then place the funnel over the sponge and slowly add water until the box is flooded. What happens to the burrows?

  9. Have a team member gently and slowly move the box back and forth on the table so students can see how water moves sand.

  10. For added discussion, consider the fate of the "animals" in their burrows. Have your students suggest all the ways animals might be able to survive the flood and write their answers on the chalkboard or overhead projector. For example, some animals might leave right away. Some might wait, then dig out. Some might be able to withstand flooding (many insects have this ability). Most species of insects, reptiles, and mammals can swim if they have to. Students may think of more creative solutions. Whatever they come up with, some animal probably does it!

In many scrub areas of Florida, there are seasonal wetlands adjacent to scrub habitat, so it is not unusual for species at the edge of scrub to have water invade their burrows.

Results
After completing Part One of this activity, students should:

  • Understand how sand behaves in water.
  • Understand the importance of drainage.
  • Understand that flooding can occur in Florida scrub during the wet season and how burrowing animals might respond.
I.A.3-Part 1    Part 2
A. Physical Properties of Sand     I.A.1     I.A.3
B. Animal Tracks in the Sand     I.B.1
C. Glossary     D. Questions for Student Evaluation