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Elements Of Chemistry: When Carbon Combines Elements-Of-Chemistry-When-Carbon-Combines?

  • Subject: Physical Science
  • |
  • Grade(s): 9-12
  • |
  • Duration: 3 class periods

Lesson Plan Sections

Student Objectives


  • Predict what happens to the glue and water solution when a borax solution is added.
  • Describe the properties of the new substance.
  • Develop a definition of polymers.

Materials


  • Elements of Chemistry: When Carbon Combines video
  • Computer with Internet access
  • Paper and pencils


  • For each group:

  • 20 ml of 55% Elmer's glue solution in water
  • 10 ml of 4% borax solution
  • Two cups
  • Stirring sticks
  • Several plastic bags that close securely

Procedures


  1. Begin the lesson by asking students to write what a polymer is and note familiar examples. If students don't know, tell them not to worry. Have them to put away the papers until the end of the lesson.
  2. Tell students that they will conduct an experiment to illustrate the properties of polymers. They will combine a solution of Elmer's glue and water with a borax solution, observe what happens, and explain their results.
  3. Before students proceed, allow time to watch the videoElements of Chemistry: When Carbon Combines . It will give important background information about carbon, hydrocarbons, and polymers.
  4. Divide students into groups of three. Make sure each group has the necessary materials. First ask the groups to predict what they think will happen when they combine a solution of Elmer's glue with a solution of borax. Encourage students to write a reason for their predictions. Then have them put their predictions away until later in the lesson.
  5. Give each group a few minutes to read the directions for the investigation, which are listed below.

    Safety Note: Unless instructed to do so, do not sniff, taste, touch, or mix any of the materials.
    • Pour 20 ml of the Elmer's glue solution into a cup.
    • Add 10 ml of the borax solution.
    • Use the stirring stick to mix the two solutions.
  6. Ask students to observe what happens to the two solutions as they are combined.(They become solid enough to form a ball.) Then ask students if they know why this happens.(The borax solution added to the Elmer's glue solution forms additional links between the covalent bonds, causing the material to become more rigid. The more links, the stronger the material becomes.)
  7. Ask one person in each group to bring the new material home; have some put it in the refrigerator or freezer for 10 minutes. Tell those students to come to class prepared to discuss what happened to the materials.
  8. During the next class period, ask volunteers to describe their observations of what happened to the material. Students should have observed that the material becomes more elastic after being refrigerated for a brief period. But it will shatter in the freezer, demonstrating that it is sensitive to temperature.
  9. Conclude the lesson by asking students to review their original ideas about polymers. Ask them these questions: Is the material you created a polymer? If so, why?

    Develop a definition of polymers that includes the following key points:
    • A polymer is a large molecule that forms when monomers, or smaller molecules, form covalent bonds.
    • In the material created, the monomers are made of hydrocarbons.
  10. Finally, encourage students to think of other examples of polymers, such as plastics, rubber, nylon, and fiberglass. Point out that these are all synthetic polymers designed for specific purposes. For example, nylon is a synthetic fiber much like silk, and fiberglass is lighter than metal and does not rust.

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Assessment


Use the following three-point rubric to evaluate students' work during this lesson.
  • 3 points:  Students easily predicted what happens when the glue and water solution was mixed with the borax solution; demonstrated a clear understanding of how to conduct the experiment; and made significant contributions to the definition of polymers.
  • 2 points:  Students predicted what happens when the glue and water solution was mixed with the borax solution; demonstrated a satisfactory understanding of how to conduct the experiment; and made some contributions to the definition of polymers.
  • 1 point:  Students did not or could not predict what happens when the glue and water solution was mixed with the borax solution; demonstrated a weak understanding of how to conduct the experiment; and made few or no contributions to the definition of polymers.

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Vocabulary


carbon
Definition: An element with the unique ability to form many compounds, largely because it can form four covalent bonds as well as chains and ring-shaped groups
Context: Carbon is found in more than two million compounds.

covalent bond
Definition: A bond between two or more nonmetals in which two atoms share electrons
Context: Carbon has the property of being able to form four covalent bonds, meaning that all four of its electrons can bond with other elements.

hydrocarbon
Definition: Compounds containing only hydrogen and carbon
Context: Two types of hydrocarbons are natural gas and petroleum, materials formed from the remains of living things found deep within Earth.

monomer
Definition: Subunits that form polymers, or long chains of molecules
Context: Most polymers are made of the same kind of monomer that is repeated in a pattern.

polymer
Definition: A large complicated molecule formed when chemical bonds link monomers in a pattern
Context: Natural polymers include cellulose and the silk in spider webs; plastic and fiberglass are synthetic polymers.

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Academic Standards


National Academy of Sciences
The National Science Education Standards provide guidelines for teaching science as well as a coherent vision of what it means to be scientifically literate for students in grades K-12. To view the standards, visit this Web site: http://books.nap.edu/html/nses/html/overview.html#content.
This lesson plan addresses the following national standards:
  • Physical Science: Chemical reactions; Structure and properties of matter
Mid-continent Research for Education and Learning (McREL)
McREL's Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education addresses 14 content areas. To view the standards and benchmarks, visithttp://www.mcrel.org/compendium/browse.asp.
This lesson plan addresses the following national standards:
  • Science ? Physical Sciences: Understands the structure and properties of matter
  • Language Arts ? Viewing: Uses viewing skills and strategies to understand and interpret visual media

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