Chicken Tonight

Location:

Concepts Shown:

iron-carbon diagram, strength, toughness, ductility, hardness

Equipment:

6 chicken bones. Try to find ones with similar dimensions, one bottle of vinegar, one glass or plastic container. It must be large enough to hold bones and have them completely submerged. A large drinking up or a clean peanut butter jar works well.

Procedure:

  1. Boil bones to remove excess fat or skin. Do not boil for extended periods of time (greater than 30 minutes).
  2. Dry bones with paper towel.
  3. Place 2 bones in a plastic bag. Label and set bag in a cool, dry place.
  4. Place 4 bones n container.
  5. Fill container with vinegar until bones are completely submerged.
  6. Check bones every 24 hours. Bones will start to become flexible. When you can squeeze the end of the bone and it compresses, remove two of the bones. Note the time it took. Rinse bones with water, dry, and place in labeled bag.
  7. Check bones every 24 hours. When last two can be bent back and forth rather easily, remove last two bones. Note the time it took. Rinse bones with water, dry and place in labeled bag. Pass out bones and let students feel the physical difference between the different bones. Discuss diagram included.
Science:

The following properties can be used to describe materials: strength, hardness, toughness, and ductility. Bone is made up of approximately 67% calcium. The calcium is removed when the bones are placed in acidic vinegar. The bone is stronger and less hard when calcium is present. It is less ductile and more tough with calcium in bone. Along those same lines, iron is stronger and less hard when carbon is present. It is less ductile and more tough with carbon in iron. Strength: Critical stress to produce failure Hardness: Resistance to penetration Toughness: A measure of the energy required for mechanical failure Ductility: Total permanent strain prior to fracture. When students touch the samples the bones without calcium will feel softer and will be bent easily. Bones with calcium will feel hard and cannot be bent. Comments: The experiment will take approximately 6 days to complete. It will proceed quicker if the bones are thin and the vinegar is strong. This demonstration is excellent in helping students understand the properties involved with the iron-carbon diagram. It lets the student actually feel the changes that occur in a material and helps them visualize concepts that tend to be confusing (tough, hard, strong). [eq].

References:

Author:
Marcia Muller
Credits:


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