Can You Find the Difference?


Students will create their own balance to determine a difference in the weight (and composition) of cents made in different years.

Coin Type(s)

  • Cent

Coin Program(s)

  • Circulating Coins


  • Students will create a balance to compare the weight of different cents (pennies).
  • Student will divide the cents into categories based on weight.
  • Students will make observations about the cents in each category.
  • Students will hypothesize why there are differences in the cents.

Major Subject Area Connections

  • Science


  • 3rd
  • 4th
  • 5th
  • 6th
  • 7th
  • 8th

Class Time

  • Sessions: One
  • Session Length: 45 minutes
  • Total Length: 0-45 minutes


  • Whole group
  • Small groups

Terms and Concepts

  • Density
  • Fulcrum
  • Simple Machines
  • Weight



  • Research changes in the composition of circulating U.S. cents using the links listed under Materials.
  • Bookmark sites for student research if desired.

Lesson Steps

  1. Tell the students that they will be working in groups to discover a secret about cents. Separate the students into groups of 4.
  2. Give each group a bag of one cent coins. Explain that there is something different about the cents in the bag that the students need to find out.
  3. Have each group create a balance using an index card and a ruler. Have them fold the index card in half to act as the fulcrum, then balance the ruler on the index card to find the balance point of the ruler.
  4. Have the students take one cent and place it on one end of the ruler, then place each of the remaining cents on the opposite end to compare their weight to the initial cent (constant), making sure they always keep the ruler at the same balance point and always use the same cent for comparison. Have them place all the coins that are equal in weight in one pile and those that are heavier in a second pile, and those that are lighter in a third pile.
  5. After the students compare all the cents, each group should have only two piles. Ask them to see if there's a pattern to the groups based on the dates on the coins.
  6. The students should note that one group contains cents minted before 1982 and the other after 1982. The students should conclude that something happened to the cent in 1982. They may have 1982 cents of both weights.
  7. Have the students speculate what the difference might be, then research on the Internet to find out what happened to the cent in 1982. There are 1982 cents of both weights because both compositions were produced that year. Have the students also hypothesize in writing why the United States Mint changed the composition of the one cent coins to include zinc in 1982 if they didn't find the reason in their research.
  8. Have the students describe their hypotheses, procedures and research results in their lab notebook.


Students can compare the weight of other coins and see if there is a difference in weight over time for them also.


Assess the written descriptions in the lab notebooks to ascertain whether the students have met the lesson objectives.

Common Core Standards

This lesson plan is not associated with any Common Core Standards.

National Standards

Discipline: Science
Domain: 5-8 Content Standards
Cluster: Physical Science
Grade(s): Grades 5–8

  • Properties and changes of properties in matter
  • Motions and forces
  • Transfer of energy

Discipline: Science
Domain: 5-8 Content Standards
Cluster: Science as Inquiry
Grade(s): Grades 5–8

  • Ability necessary to do scientific inquiry
  • Understand scientific inquiry