Directions 1. Introduce the unit to students. Tell students that in a week from now, they will begin to study how things decay. To prepare for that, they will set up the investigation by putting bread in Petri dishes, recording data, and keeping the bread in a warm, dry place for a week. 2. Divide students into groups of four. Give each student a copy of Pre 1.1 Bread Mold Investigation Set Up Worksheet. Tell they that they will use these to record their data now and also in a week, so they should be sure to keep track of their worksheets. 3. Demonstrate the investigation set up. Demonstrate the set up for students, making sure they understand how to use the digital balance to determine the mass of their Petri dishes. Use the Pre Lesson Bread Mold Investigation Worksheet to guide your demonstration. Note: Mass is a measure of how much matter is in a system, weight is a measure of the gravitational pull on that system. 4. Have students set up the investigation. Have students set up their investigation by following the steps in the Pre 0.1 Bread Mold Investigation Set Up Worksheet. Students should check off each step of the investigation when they have completed it. The worksheet includes instructions on where and how to record data. This involves: Each student preparing one Petri dish with bread sprayed with water; Each student labeling the Petri dish with his/her name; Each student finding and recording the mass of his/her Petri dish on his/her worksheet. Each student calculating the total mass for his/her group’s bread and Petri dishes. 5. Have students record each group’s data on the poster or spreadsheet. Students can record their data in one of two ways: in the Bread Mold Class Results Spreadsheet or on the Bread Mold Class Results 11 x 17 Poster. We recommend using the spreadsheet if possible because it will automatically calculate mass loss and also generate a graph of the data. Spreadsheet Option: Project this spreadsheet and open Tab 1 – Individual Data. Ask individuals to report the mass of their individual Petri dish and bread. As data are added, the spreadsheet will automatically populate the data on Tab 2 – Group Data and Averages. Poster Option: Alternatively, students can record their data as a group on the Bread Mold Class Results 11 x 17 Poster, which can be posted on the wall. Students will have their group’s total mass on their worksheet. 6. Have students store their bread and Petri dishes in a cool, dry place. Tell students that they will revisit their bread in a week to look for changes. Until then, they should store their worksheet and bread in a place where they can find them easily in a week.
