How are materials the same and different?

Turning to the class table, ask all the students who are pine “experts” to meet, compare notes, and write their descriptive words in the first column. Watch for duplicates, and encourage use of words that will aid in comparison, e.g. color, odor, and texture. Occasionally ask a student to defend a description, e.g.,

• What do you mean the acrylic is transparent? Show me.

If students do not understand a description, or if there is disagreement about an attribute, pass the cube around for further investigation. The Investigation Question is about similarities and differences, so consensus is important. Continue through the set of materials until the table is complete.

Students will likely describe the pine cube as “light” and the copper cube as “heavy”. To help students make an initial distinction between “heavy” and “heavy for size” raise the following questions:

• What about a very big piece of pine? Would it be light?
• What about a very small piece of copper? Would it be heavy?
• So is simply being “heavy” or “light” a property of the material or of the cube?
• What might be a better way to describe what is different about pine and copper?

The pine cube is “lighter for its size”, the copper is “heavier for its size”. If you had two very large cubes of pine and copper, both would be heavy, but the copper would be much heavier for its size. Similarly, if you had two very small pieces of pine and copper, both would be light, but copper would still be heavier for its size. Encourage them to list heavier and lighter for size as a property of materials.

Once the table is complete, tell students that there is a special word to describe the qualities of a material; that word is properties. Model the use of the word:

• The properties of pine include … (read the students’ list).
• The properties of oak include … (read the students’ list).