Elicit non-trivial dialogue from students. Guide students to reflection and analysis of the experience. Encourage students to share their perceptions and beliefs. Summarize and review similarities and differences.

Discussion and analysis of group problem solving procedures.

Objective: To analyze the effectiveness of their estimation.

Activity: Each group displays its sample and explains how they arrived at their estimates. Teacher leads discussion focusing on the following: 1. Difficulties experienced in trying to estimate. 2. Types of particles which were easier to estimate and which were hardest. 3. Is it possible to know how many atoms or molecules are in a sample? 4. Which jars contain samples which could be called "singles" and which could be called multiple units? 5. What problems would occur if a sample contains an exceedingly huge number of particles? Teacher tells students with countable samples (marbles, pennies, etc.) how many particles were really in their sample. Ask students to name units they are familiar with which are used to count pieces in a sample; examples are pair, dozen, score, etc. Have them generate as many terms as possible.

Assessment: Contributions to small group effort and large group discussion.