You be Forcin’ It

Keith Zeise and Michael Lawton

Abstract:

This is an inquiry-driven lesson with many layers that is structured utilizing the 7 E’s learning cycle approach (elicit, engage, explore, explain, elaborate, evaluate, extend). The concept taught is inter- and intra-molecular forces. The lesson consists of several demonstrations and quantitative experiments where students create their own model about inter- and intra-molecular forces, are formally introduced to the concept, and then apply the model to several new situations.

About the 7 E’s

The 7 E model is a constructivist, inquiry-driven, learning-cycle type approach to teaching. It uses the following steps.

  1. Elicit. Probe the students’ preconceptions about a topic. This can serve as a cognitive anchor with which they can build upon.
  2. Engage. Prick the students’ interest in the topic. This can be a discussion, video, or demonstration that generates curiosity or concern with the topic. Discrepant events work well here.
  3. Explore. The students develop their own cognitive models about the topic. They can do their own research or experiments.
  4. Explain. The teacher presents the concept or model that the students will be working with.
  5. Elaborate. The students use the concept or model in a new situation or situations. They articulate how the model applies.
  6. Evaluate. The students analyze the effectiveness of the model in new situations, and critique their own and/or each others’ processes.
  7. Extend. The students apply their learning and make it relevant in real life situations, or interdisciplinary applications.

7 E’s Lesson Plan

Elicit

Present the students with this question and discuss the justifications for their answers.

When water evaporates by boiling, circle all of the following things that occur.

  1. Water splits into hydrogen and oxygen
  2. Water molecules increase their distance from each other
  3. Air bubbles are produced
  4. Water chemically reacts with air to produce bubbles
  5. Bubbles contain oxygen and hydrogen gas

Engage

Engage the students with any or all of the following discrepant events.

  • Pepper afraid of soap demo: sprinkle pepper on a wide surface of water; add one drop of dish soap and the pepper sprinkles “shoot” to the sides of the water.
  • Floating pins or paperclips: gently rest a few paperclips or pins on the surface of clean water (the more pure the water, the easier it is) and they will float! Using a plastic fork to “rest” them on the surface of the water can help.
  • Lycopodium powder or magic sand: Fill a 250mL beaker 2/3 full with water. Lycopodium powder will float on the surface and you can “dip” your finger in it and your finger will come out dry. “Magic sand” can be ordered from science catalogues, it is a sand that when added to water, will come out dry because it has a nonpolar substance coating it.

Explore

Students will carry out a quantitative experiment measuring the viscosity of several pure liquids.

Chemicals needed: Hexane, propanol, propylene glycol, and glycerol. This list is by no means definitive. These chemicals were chosen for their differences in the number of OH groups. Other chemicals may be chosen based on preference and/or availability.

Materials needed: 10mL pipettes (4 per lab group recommended; any kind of small-diameter passageway will suffice, such as a burette, glass tubing, or test tubes), protractors and books (or any objects to establish a consistent angle), ball bearings, stopwatches.
Procedure:

  1. Place 10mL of each chemical in separate pipettes. Label each one’s contents.
  2. Set the pipettes at a 30° angle using the protractors and other objects. This angel can be increased or decreased to create a more optimal time (not too fast and not too slow).
  3. Drop a ball bearing into each pipette at the same time as starting the stopwatch.
  4. Record the time that it takes each ball bearing to reach the same distance in each pipette.
  5. Repeat trials as time allows, doing each liquid at least twice.

Some technique suggestions:

  • For accurate distance and timing, drop the ball, let it move until a specific mark (either a mL mark, or one you tape on yourself) on the tube, start the stopwatch, and stop at another specific mark.
  • To repeat trials, multiple balls can be used, or the pipette can be tipped back to let the ball return to the top, or a steel ball can be employed to use a magnet to “drag” the ball back to the top. However, steel balls may rust over time.
  • The pipette apparatus can be “permanently” sealed using stoppers, glue, or whatever means, so that students can simply be given the apparatus, and it reused year after year.

Explain

Teacher presents concepts and vocabulary of intermolecular and intramolecular forces. Possible vocabulary introduced includes partial charges, polar, nonpolar, hydrogen bonding, dipole-dipole forces, Van der Waal’s forces. Velcro balls, baseballs and paddles are excellent models to illustrate these concepts kinesthetically. Intermolecular forces attract the Velcro balls to the paddle. Baseballs lack the attractive forces, so they do not stick to the paddle. However, if the Velcro ball is thrown hard enough, it too will bounce off, just like adding enough heat to water so that the particles overcome their attraction and boil.

Elaborate

Students quantitatively measure the evaporation rate of the following substances. They can carry out all steps of the scientific method, including: developing a hypothesis, writing a procedure, collecting, representing, and analyzing data, and writing a conclusion. The chemicals listed are a suggested list, but by no means definitive. They represent several different kinds of forces that will influence their evaporation rate.

  • Hexane (adequate ventilation required)
  • Acetone
  • Ethanol
  • Water
  • Water with different substances dissolved in it.

Suggestions for a procedure:

  • Students can weigh cotton balls, paper, any other absorbent material, or put it on a non-absorbent surface (because an absorbent material may have different degrees of attraction to the different liquids-which itself may be an area to spark discussion) add the liquid, and then weigh them again. They can wait a specified amount of time and re-weigh the items, or time how long it takes for the item to dry.
  • Students can wet an absorbent material a certain distance or diameter, and then measure the distance after an amount of time, or time how long it takes for the entire liquid to dry.

Evaluate

Students will present their findings. Students should come up with data-driven conclusions, address their hypothesis, critique the strengths and weaknesses of their procedure, propose improvements to their procedure, and suggest further research that could be done.

Extend

Students connect intermolecular forces with biochemistry in investigating current research being done on protein folding, DNA structure, and genetics. This research can be done independently and students can present their findings in the form of a paper, poster, or presentation.

Standards Addressed:

This module addresses multiple content standards according to MPS, Wisconsin, and national benchmarks. Specifically, these involve science connections, science inquiry, and the structure of atoms and matter. Below is a thorough list of the standards addressed at these levels.

Science Connections

Milwaukee Public Schools (MPS) Learning Target:

Conduct scientific studies using models, scientific methods, including data collection, analysis, and other research tools to study systems similar to those found in nature or human made.

Wisconsin State Academic Standards:

Science Connections

A12.3Give examples that show how partial systems, modes, and explanations are used to give quick and reasonable solution that are accurate enough for basic needs

A12.5Show how the ideas and themes of science can be used to make real life decisions about careers, work place, life-styles, and use of resources

A12.7Re-examine the evidence and reasoning that lead to the conclusion drawn from the investigations using the scientific themes

National Content Standards:

Unifying Concepts and Processes: systems, order, organization; evidence, models, explanation; change, constancy, measurement; evolution and equilibrium; form and function

Nature of Science

MPS Learning Target:

Explain how scientific knowledge is attained. Describe the ethical problems that may result when doing scientific research. List scientists from various backgrounds and tell about their contributions.

Wisconsin State Academic Standards:

B12.4Show how basic research and applied research contribute to new discoveries, inventions, and applications

B12.5Explain how science is based on assumptions about natural world and themes that describe the natural world

National Content Standards:

G. History and Nature of Science:Science as a Human Endeavor, Nature of Scientific Knowledge, Historical Perspectives

Science Inquiry

MPS Learning Target: Research scientific concepts

Undertake scientific investigations using appropriate scientific methods, technology, and tools. Use computer-based technology, mathematics, and scientific vocabulary to communicate results.

Wisconsin State Academic Standards

C12.1When studying science content, ask questions suggested by current social issues, scientific literature, and observations of phenomena, build hypotheses that might answer some of these questions, design possible investigations, and describe results that might emerge from such investigations

C12.2Identify issues from an area of science study, write questions that could be investigated, review previous research on these questions, and design and conduct responsible and safe investigations to help answer the questions

C12.3Evaluate the data collected during an investigation, critique the data collection procedure and results, and suggest any ways to make any needed improvements

National Content Standard- A. Science as Inquiry:

Abilities to do Scientific Inquiry (Identify Questions and Concepts that Guide Investigations, Design and Conduct Scientific Investigations, Use Technology and Mathematics to Improve Investigations and Communications, Formulate and Revise Scientific Explanations and Models Using Logic and Evidence, Recognize and Analyze Alternative Explanations and Models, Communicate and Defend a Scientific Argument) and Understandings about Scientific Inquiry

Structure of Atoms and Matter

MPS Learning Target:

Diagram the structure, and analyze the chemical reactions of elements. Explain the forces that hold the atom together, and how nuclear interactions change it. Describe the difference between chemical reactions and atomic reactions.

Wisconsin State Academic Standards

D12.1 Describe atomic structure and the properties of atoms, molecules, and matter during physical and chemical interactions

D12.2 Explain the forces that hold the atom together and illustrate how nuclear interactions change the atom

D12.4 Explain how substances, both simple and complex, interact with one another to produce new substances

D12.5 Identify patterns in chemical and physical properties and use them to predict likely chemical and physical changes and interactions