Paper Clip Sailing

This lesson developed by Reach Out!

Guiding Question:

1. Why do some things float on top of water?

2. What is surface tension?

Objectives

Concepts

• Some things can float on top of water because of what we call "surface tension."

Principles:

• Surface tension happens when the water molecules on the bottom are pulling and tugging on the water molecules on top, as though to try and pull them down under with them.
• Surface tension creates something similar to a skin layer on the top of the water.

Facts:

• Some things can float and stay on top of the water because of this skin-like surface caused by surface tension.
• If something happens to disturb these water molecules from tugging on each other, the skin-like surface breaks up.
• When something is floating on the top of water and the surface tension gets interrupted, it will sink.

Skills

• Making Observations
• Making Comparisons
• Documenting Findings
• Communicating Findings

Materials:

1. A clear glass or plastic salad or mixing bowl
2. Water
3. Fork
4. Paper clip
5. Dish Soap

Room Preparation

Need ample elbow room. Spills may happen.

Safety Precautions

None.

Procedures and Activity

Introduction

• Begin by asking, "Why do some things float on top of water?"

  Share ideas, experiences, and examples. Probe possible explanations for why anything would possibly be able to stay on top of water.

• Ask, "What is surface tension?"
  First, talk about the word "surface." Come up with a definition everyone can agree upon. Then, think about "tension." Rub hands together. You can feel tension due to the pressing and movement of the palms of your hand. The result is we can feel heat from the friction created by the rubbing and tension. Introduce the idea of water surface tension and the notion of little water molecules below the surface pulling and tugging, trying to get the water molecules on top to join them underneath.

• Today, we are going to do an experiment to better understand water surface tension. We will see that surface tension is directly related to the ability of some objects to float and stay on top of water.

Activity

1. Fill clear bowls with water.

2. Now comes a balancing act! Hold the fork with one hand and rest the paper clip on the prongs.

3. Slowly and carefully sit the fork into the bowl of water until the paper clip floats off the fork and rests on top of the water. This may take some practice!

4. Why doesn't the paper clip sink? Squat down to get eye level with the bowl of water. Observe what is happening. Can you see how the paper clip is a little bit down in the water? Or does the paper clip totally rest on top? Can you see kind of a surface or skin-like appearance on the very top of the water?

5. We are seeing evidence of water surface tension.

6. Put a drop of dish water soap into the water. Put it in somewhere away from where the paper clip is floating. What do you think will happen?

7. Why does the paper clip sink down into the water? What did the soap do? Share ideas. If no one comes up with it, share that when we added the drop of soap, we interrupted the pull and tug of the water molecules on top and below. This broke up the force and skin-like surface on top, so the paper clip dropped.

8. Repeat experiment and encourage use of terms: water, molecules, surface, and surface tension.

Evaluation

Again, ask the guiding questions:

1. Why do some things float on top of water?

2. What is surface tension?

Listen for evidence that they have come to a better understanding about water, molecules, and surface tension. If possible, have them share this lesson and experiment with others. When we "teach" something, we definitely come to understand it! This is a fun experiment to share with friends.

• It is fun to use paper clips and make more complicated sailing vessels! Try different designs and see if they will float.

• Research and learn about the flotation design of other boats or a seaplane. Learn more about surface tensions by gathering information about these vessels.

• Look up information about water striders and other insects that float on water surfaces. How are they built so they will float?

Careers Related to Lesson Topic

• Aeronautical Occupations
  • Tour- Michigan Insitute of Aeronautics

  • Presentation- Michigan Insitute of Aeronautics

  • Tour- Yankee Air Museum

• Chemist
  • Wizard- Uldis Krolls "Whiz Bang Chemistry"

• Naval Architecture and Marine Engineering
  • Tour- Virtual Reality Lab

  • Tour- Marine Hydrodynamics Laboratory

  • Career Presentation- University of Michigan Navy ROTC

• Naval Science and Nuclear Engineering
  • Career Presentation- University of Michigan Navy ROTC

Prerequisite Vocabulary

Molecules

The smallest amout or unit of a substance, like water, that still has all the parts of the origial substance.

Surface Tension

When the molecules of water inside the bowl attract and pull on the molecules of water on the top surface. This is called "surface tension." It is as though the water molecules below the surface are pulling and tugging on the water molecules at the top.

Water

The liquid that comes from clouds as rain and creates the streams, rivers, lakes and oceans on our Earth.