Pepper Scatter (Athena Meltzer)

Author

Athena Meltzer

Principle(s) Illustrated

• Surface tension is the result of the strong attraction between molecules in a liquid. Water has an unusually high surface tension compared with most other liquids because water molecules are very strongly attracted to each other. This strong attraction allows you to slightly overfill a glass with water and some insects to skate on its surface. Water molecules on the surface pull away where you add detergent.

• NGSS Science & engineering standards

  • Developing and Using Models

    • Modeling in 6–8 builds on K–5 and progresses to developing, using and revising models to describe, test, and predict more abstract phenomena and design systems.

• • • • Analyzing and Interpreting Data

• NGSS Cross-cutting concept standards

  • Patterns

    • Macroscopic patterns are related to the nature of microscopic and atomic-level structure. (MS-PS1-2)

  • Cause and Effect

    • Cause and effect relationships may be used to predict phenomena in natural or designed systems. (MS-PS1-4)

• NGSS Disciplinary core idea standards

  • • PS1.A: Structure and Properties of Matter

  • Substances are made from different types of atoms, which combine with one another in various ways. Atoms form molecules that range in size from two to thousands of atoms. (MS-PS1-1)

    • Each pure substance has characteristic physical and chemical properties (for any bulk quantity under given conditions) that can be used to identify it. (MS-PS1-2),(MS-PS1-3)

Questioning Script

Prior knowledge & experience:

• When soap detergent is added to water it will help clean the dishes by cutting the grease.

Root question:

• Prediction: What will happen to the pepper when I touch the middle with my finger?

• Prediction: What will happen to the pepper when I tough the middle with a drop of detergent?

• Question: Why did the pepper not move when I touched my finger to it but when I touched the water with a Q-tip covered with detergent the pepper all moved to the sides of the container?

Target response:

• The motion results from the reduction in the water's surface tension when detergent is added.

• detergent molecules are attracted to water, but not nearly as strongly as water molecules are attracted to each other. This is why detergents reduce the surface tension of water.

• Could also ask kids about animals they know that rely on surface tension and how adding detergents to the water might affect their ability to survive in their environment.

Common Misconceptions:

The detergent will actually mix with the water to form bubbles and the molecules of water and detergent will combine.

Worksheets:

Surface Tension

Photographs and Movies

Pepper Scatter

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References

Surfing Scientists

Pepper Scatter Lesson Plan