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Naturally Hydrophobic

Grades: 9-12
Author: Danielle T. Moore
Source: This material is based upon work supported by the National Science Foundation under Grant No. EEC-1161732.


Abstract

In nature, hydrophobic systems occur all around us. One such natural phenomenon is the hydrophobicity exhibited in roses and their petals. Another is the hydrophobicity of lotus leaves. The naturally non-wetting surface has micro-scale surface layer properties which create a relative high contact angle when contacted with water. Using contact angle measurements, students will investigate different commercial hydrophobic coatings. Students knowledge of surface chemistry and effective use of skills related to observations, measurement, data analysis and critical thinking will be used to design a multi-tiered experimental design. Students will utilize process to make accurate decisions supporting or disproving manufacture claims of product effectiveness.


Objectives

What should students know as a result of this lesson?

  • Science Inquiry and Application
  • All students must use the following scientific processes with appropriate laboratory safety techniques to construct their knowledge and understanding in all science content areas:
  • Identify questions and concepts that guide scientific investigations; (1)
  • Design and conduct scientific investigations; (2)
  • Use technology and mathematics to improve investigations and communications; (3)
  • Formulate and revise explanations and models using logic and evidence (critical thinking); (4)
  • Recognize and analyze explanations and models; (5)
  • Communicate and support a scientific argument. (6)
  • Intramolecular Chemical Bonding
  • Compounds containing carbon are an important example of bonding, since carbon atoms can bond together and with other atoms, especially hydrogen, oxygen, nitrogen and sulfur, to form chains, rings and branching networks that are present in a variety of compounds, including synthetic polymers, fossil fuels and the large molecules essential to life.

What should the students be able to do as a result of this lesson?

  • Students will be able to utilize scientific inquiry processes to make accurate decisions supporting or disproving manufacture claims of product effectiveness after analyzing hydrophobic properties of commercially available synthetic polymer.

Materials

  • Hydrophobic (water repellant) coatings. One coating will be investigated in Part I of the lesson, In Part II three other coatings will be investigated. A superhydrophobic coating is the two part NeverWet liquid repelling treatment from Rustoleum and is suitable for Part I. Rustoleum also makes a one part spray bottle solution. Other choices of water repellants include Scothgard water repellant, Rain-x, Car wax (e.g. Turtle wax). Any of these water repellants may be substituted in Part I. These water repellants can be purchased from on-line retailers or a large discount retail stores (e.g. Walmart, Target, K-Mart)
  • Glass slide
  • Aluminum Foil
  • Camera/Smartphone
  • Protractor/Ruler
  • Metal, Wood, Plastic, etc.

Procedures

Engagement/Assessment

Students will utilize hands-on trouble shooting to coat and test various samples. Students will use active learning to ensure every member of the group participates.

Observations of student participation and accountable conversations as well as written observations can be used as assessments.

Exploration/Assessment

Students will perform research on products creating hydrophobic effect in addition to research on the chemistry of surface structures.

Students will present and/or substantiate effectiveness of product samples.

Explanation/Assessment

Students will provide written evidence of learning throughout the lab process.

Students written observations will be checked for accuracy throughout investigation. Students will also provide verbal explanations when prompted.

Elaboration/Assessment

Students will test various products and materials to determine the variation in surface chemistry among researched materials.


Prerequisites

N/A


Best Teaching Practices

  • Cooperative Learning
  • Writing Across the Curriculum
  • Interactive Learning
  • Accountable Talk
  • Research Based
  • Real World Connections

Alignment with Standards

NGSS Standards:

  • HS-PS1-1. Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms
  • HS-PS1-2. Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
  • Disciplinary Core Ideas: PS1.A: Structure and Property of Matter, PS1.B:Chemical Reactions, PS2.B: Types of Interactions
  • Science and Engineering Practices: Developing and Using Models, Planning and Carrying Out Investigations

Common Core Standards:

  • RST.11-12.3. Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performingtechnical tasks; analyze the specific results based on explanations in the text.
  • WHST.11-12.1. Write arguments focused on discipline –specific content.

Ohio Standards:

  • PHYSICAL SCIENCE: Science Inquiry and Application; Study of Matter: Classification, Atoms, Periodic Trends of the Elements, Bonding and Compounds, Reactions of Matter
  • CHEMISTRY: Science Inquiry and Application; Structure and Properties of Matter; Interactions of Matter

Content Knowledge

Basic understanding of physics and chemistry is needed. Students may integrate smart phone and/or other devices for protractor applications and contact angle measurements.


Safety

Product application should be performed under a fume hood or well-ventilated area. The manufacturer instructions for applying coatings should be followed. Standard lab safety rules apply. Students should thoroughly wash hands after lab and avoid contact with eyes.


Applications

Students' knowledge of hydrophobic properties and investigation will lead to improved consumer choices. Students can also deepen understanding of polymer structure and synthesis to increase knowledge of molecular chemistry for collegiate and/or industrial usage.


Assessment

Completed Lab Worksheets


Other Considerations

Grouping Suggestions: Student groups should contain students of all ability levels. Students may be assigned (or self- select) roles to ensure equal student participation and accountability.

Pacing/Suggested Time: 2 – 40 minute class periods


Printable PDF Worksheets

Naturally Hydrophobic: Investigating Contact Angle Lab Worksheet