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8.1: Investigating Static Forces in Nature: The Mystery of the Gecko

Created by: CK-12

Slide 2

How do the spatula-shaped tips of the setae come into close contact with the surface?

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Slide 3

How is the gecko seta similar to the transparent tape example?

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How is the gecko seta different than the transparent tape example?

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Slide 5

1. What is the effect of placing a negatively charged player (red dot) close to the path of the positively charged soccer ball (blue dot)?

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2. What is the effect of placing a positively charged player (blue dot) close to the path of the positively charged soccer ball (blue dot)?

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3. What are your thoughts about the gecko seta surface and the ceiling surface as they relate to charges?

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Slide 6

Exploring Attractive Intermolecular Forces Animation

Each object represents a molecule. The green molecules are non-polar, which means they have no charge. The red/blue molecules are polar meaning one end is positive and the other is negative (like a bar magnet).

Below are three illustrations of weak attractions between molecules as shown in the animation. Identify the illustration that shows:

  1. The attraction between two polar molecules. _____________________________
  2. The attraction between two non-polar molecules. _________________________
  3. The attraction between a polar and non-polar molecule. __________________

View the animation. The dashed lines represent an attraction.

4. What makes you think that these attractions are weak?

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5. Are these permanent or temporary attractions? How long do they last?

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How do you think two non-polar (neutral) molecules attract since they have no charge? Let’s find out!

Slide 7

  1. What is the overall charge of each atom in this diagram? ______________________
  2. In the diagram, what side of the atom is more negative? _______________________
  3. Not including the nucleus, what side of the atom is less negative? ____________
  4. Would the two atoms attract or repel? ________________________

Explain

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Slide 8

1. What is the overall charge of each atom in this diagram?

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2. Would the two atoms attract or repel?

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Explain your answer

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Slide 10

1. Which molecule has the most contact with the green molecule?

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Explain your answer

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2. Explain how shape affects the number of attractions between the object and the surface.

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3. Which molecule acts most like the gecko seta?

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Explain your answer

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Slide 11

1. Describe the number and strength of forces involved in gecko adhesion.

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2. What part of the atom moves in response to momentary charge rearrangements?

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3. Describe this interaction between the electrons of each atom. Describe the overall charge and how long the attraction lasts.

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4. Looking at the Adhesion Methods Debrief Chart from Lesson 5, which adhesive method matches most closely with what you have learned?

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Essay Assessment: Demonstrate Your Understanding

Write a short essay in response to the prompt below. Base your essay on what you have learned about gecko adhesion throughout the module. You may refer to your journal to help you plan your response; however, the writing in the essay should be distinct from your journal and be written in your own words (i.e., no copying). Your response to the prompt should not exceed one page. You may use diagrams to illustrate concepts; however, the diagrams should reinforce your written explanations not replace them.

Writing Prompt

Explain how the gecko can adhere to a ceiling. Your written explanation should include the following:

  • Describe (with words and/or drawings) the surface-to-surface interactions between gecko “setae” and a ceiling. Be sure to address the characteristics of both the setae and the surface. Include the shape, number, and size of setae in contact with the surface.
  • Describe the variables affecting adhesion: the surface area, the surface contact, and the type of surface.
  • Explain how a lot of tiny adhesive forces overcome the force of gravity.
  • Describe the electrical forces and their role in gecko adhesion (i.e., interactions of charged particles between atoms of the spatula and the ceiling surface).

Refer to the instructional rubric on the next page to learn of the criteria that will be used to evaluate your writing.

Instructional Rubric for Essay Assessment
Criteria Advanced (4) Proficient (3) 'Partially Proficient (2) Novice (1)
Writing Style and Mechanics Concise, clear, and engaging explanations with flawless spelling, punctuation, and grammar. Concise and clear explanations with minor errors that do not interfere with communication. Appropriate writing format. Writer does not appear to have carefully proofread. Demonstrates little or no attention to the writing format. Has great difficulty communicating.
Understanding of Content
  • Explanations are complete* and detailed, demonstrating a sophisticated understanding of surface-to-surface interactions and forces affecting adhesion.
  • Writes in own words using common & scientific language.

^*Responses include answers to all four bullet points in the prompt.

  • Explanations are complete* demonstrating an understanding of surface-to-surface interactions and forces affecting adhesion.
  • No clear inaccuracies or misconceptions.
  • Mostly writes in own words using common & scientific language.

^* Responses include answers to all four bullet points in the prompt.

  • Explanations demonstrate a basic understanding of surface-tosurface interactions and forces affecting adhesion.
  • May contain inaccurate or incomplete information.
  • Writes using scientific language only, not always writing in own words.
  • Explanations are missing important information.
  • Does not demonstrate a basic understanding of surface interactions and forces affecting adhesion and/or contains inaccuracies.
  • Writing is not in own words.

Investigating Static Forces in Nature: The Mystery of the Gecko

Lesson 8: How Can a Gecko Walk on a Ceiling?

Student Journal

© 2009 McREL

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Feb 23, 2012

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Dec 11, 2013
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