Akron Global Polymer Academy Lesson Plans

Exploration of Bone as a Natural Composite Material

Grades: 9-12
Author: Danielle Donaldson
Source: Original - This material is based upon work supported by the National Science Foundation under Grant No. EEC- 1542358.

Abstract

Growing up we were told to drink our milk so that our bones could grow to be strong. Milk and other food products provide us with the calcium our bones need for strength. In fact, about 99% of our body's calcium is found in bones. However, our bones also need a structural protein called collagen in order to provide added strength and flexibility. Bone can be thought of as a composite material; something made out of two materials with different properties, which when brought together produce a new material with new properties. In this laboratory you will play the role of a polymer scientist and explore the techniques that engineers use to test the strength properties of a composite material.

Objectives

What should students know as a result of this lesson?

• Students should be able to identify the significance of calcium and collagen to bones
• Students should be able to define what a composite material is
• Students should be able to understand the importance of both collagen and calcium to the overall mechanics of a bone
• Students should be able to identify the rule of mixtures and explain how engineers use this rule when making composites
• Students should be able to relate the mechanics testing done in this activity to that which is done by engineers in a laboratory setting

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

• Students should be able to make measurements and record observations about the three chicken bones
• Students should be able to construct testing apparatus and effectively use it to conduct bending test
• Students should be able to report their findings and draw conclusions about the importance of collagen and calcium to the bone
• Students should be able to relate data collected in the laboratory to the rule of mixtures
• Students should be able to follow all safety instructions

Materials

• Chicken Bones (leg, cleaned) 3 per student/group
• Vinegar
• Oven
• 5 gallon bucket
• S hook or carabiner
• 2-3 feet of chain link
• 5 pound weights (at least 10 of them); or some equivilent weight material such as water, sand, bricks, gravel, etc.
• Electronic mass
• Ruler
• Duct tape
• Permanent Marker
• Student Worksheet

Procedures

Engagement

Show students the youtube clip: https://www.youtube.com/watch?v=WRIm6AXBK34 "Bone Strength: More Than Just Calcium" and ask students if they know what polymers are. Have a discussion with students about composites and discuss the connection between composites and bones. Tell students that you will be looking at strength properties of bones in a way that an engineer would.

Introduction

Growing up we were told to drink our milk so that our bones could grow to be strong. Milk and other food products provide us with the calcium our bones need for strength. In fact, about 99% of our body's calcium is found in bones. However, our bones also need a structural protein called collagen in order to provide added strength and flexibility. Bone can be thought of as a composite material; something made out of two materials with different properties, which when brought together produce a new material with new properties. In this laboratory you will play the role of a polymer scientist and explore the techniques that engineers use to test the strength properties of a composite material.

Composites

Composites can be found everywhere in our lives. Some examples of engineered and natural composite materials are:

• Concrete
• Plywood
• Fiberglass
• Bone
• Teeth
• Wood
• Shells

For polymer engineers making composite materials can be beneficial because they often times have properties more valuable than the materials they are made out of. Engineers often use mechanical tests to gain information about the the properties of a material. In this lab you will be conducting stress tests on bones that have had either the calcium or the collagen removed and compare the properties of these bones to a normal chicken bone.

Exploration

Procedures

1. Place the "calcium deficient bones" in a beaker of vinegar so that the vinegar is covering all parts of the bone. Let this soak for at least 3 days.
2. Place the "collagen deficient bones" on a baking tray and bake at 250 °F for 3 hours.
3. After treatments are complete, measure the three bones (control, calcium deficient, and collagen deficient) and use a permanent marker to make a mark on the middle part of the bone.
4. Observe properties of the three bones and record information in Table 1.
5. Set up the loading area as follows (this can be done as a whole class or per group depending on materials) for the untreated bone:
   1. Move two tables together so that they are 2-inches apart.
   2. Using either an S-hook or carabiner, hook a chain to the bucket handle.
   3. Place the bone across the gap in the tables and secure each side with duct tape.
   4. Hook the chain the bucket around the bone, making sure it is over the middle part of the bone.
   5. Add weight carefully in 5 lb. increments to the bucket. Make sure to pause for at least 30 seconds in between each weight to assess for bone breaking.
   6. Continue to add weight unless the bone cracks or breaks.
   7. Record the breaking weight in the data table.
6. Repeat this procedure for the vinegar and baked bones. Record results in the Table 2.

Explanation

Have students answer and discuss the following analysis questions:

Analysis

1. What differences did you see between the treatments?
2. Why is having both calcium and collagen important to bones? How does this relate to the Rule of Mixtures? What is another composite material and what is it used for?
3. Bioengineers are currently researching ways to make artificial bones or bone scaffolds to repair fractures or damages to the bone. What are some important properties that the artificial bone must have in order to function?
4. What are some other ways that engineers would have to test an artificial bone other than the setup we created in order to see if it would be successful?

Elaboration

Extension

For physics or engineering students, elastic modulus of the bone could be calcuated. In addition, students could explore the challenges in making an artificial bone by either doing research or using polymers to make a strong yet lightweight material.

Prerequisites

Students should be able to follow directions, follow safety instructions, and work together with partners. Students should be able to make measurements and collect data. Students must have some algebra abilities to work with the rule of mixtures equation.

Best Teaching Practices

• Teaching for Conceptual Change
• Hands on/Minds on Learning
• Real Life Situations and Problem Solving
• Learning Cycle

Alignment with Standards

NGSS Standards:

• HS-LS1-1. Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.
• HS-LS1-2. Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.
• HS-ETS1-1. Analyze a major global challenge to specify qualitative and quantitative criteria and constraints for solutions that account for societal needs and wants.
• HS-ETS1-2. Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering.
• HS-ETS1-3. Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics, as well as possible social, cultural, and environmental impacts.

Ohio Standards:

• Identify questions and concepts that guide scientific investigations;
• Formulate and revise explanations and models using logic and evidence (critical thinking);
• Design and conduct scientific investigations;
• Communicate and support a scientific argument

Content Knowledge

Collecting Scientific Measurements and Data

Laboratory Safety

Engineering Design

Safety

• Students should wear gloves when handling the bone, as some tissue material might still be on them
• Students should wear goggles to protect from bone fragments
• Use proper disposal procedures for all materials

Applications

Most students understand that calcium is needed in our diet to keep our bones strong, but most do not realize the importance of flexibility in order for bones to bear a load. This lesson connects a material that students are familiar with to the rule of mixtures that engineers use when creating a composite material. Students will also gain experience in material testing and understand the things that engineers need consider when testing materials for many types of applications (construction, biomedical, electronics, etc.)

Assessment

Laboratory report can be collected for summative assessment of lesson content.

Other Considerations

Grouping Suggestions:

• Since materials are limited it is best that students are put into groups of 2-4 students
• Cooked chicken bones or raw can be used for this experiment; but raw is preferred
• Untreated chicken bone can be tested as a whole class in order to save class time/materials

Pacing/Suggested Time:

• Bones must soak in vinegar for a couple of days so it would be best to start this experiment on a Friday and let them soak over the weekend. Plan accordingly to allow the bones to soak for at least 3 days.

Printable PDF Worksheets

• Exploration of Bone as a Natural Composite Material Worksheet

Safety Disclaimer