Three-dimensional Learning Progression Pre-Lesson should be conducted at least seven days before you plan to begin the Decomposers Unit. Key Ideas and Practices for Each Activity In Pre-Activity 0.1, students set up an investigation that allows them to measure mass change in moldy bread over the course of a week. This sets the stage for students to be able to ask questions about what is happening to matter and energy during the decay process. Note: Bread that appears to have no mold growing on it might actually have mold that is invisible to the naked eye. Students may have initial ideas about the Three Questions for moldy bread, which will be recorded in Lesson 1. A note on mass and weight: Grams and kilograms in the SI (metric) system are units of mass—the amount of matter in a system. On the other hand, pounds and ounces in the English system are units of weight—the force of gravity on a particular mass. As long as gravity doesn’t change, these units are interconvertible: The force of gravity on a 1 kg mass is about 2.205 pounds. Since most American students are more familiar with the English units of weight, we sometimes use “weigh” and “weight,” especially when encouraging students to express their own ideas. When referring to measurements in grams, we use “mass” as both a verb and a noun Content Boundaries and Extensions
