Directions 1. Use the instructional model to show students where they are in the course of the unit. Show slide 2 of the Pre-Lesson 0.1GL Measuring the Mass of Solids in Mixtures PPT. 2. (Day 1) Introduce the unit to students. Tell students that in 3-4 weeks from now, they will begin to study plant growth. To prepare for that, they will set up the investigation by planting seeds prior to the unit, recording data, and making sure the plants grow over the next few weeks. 3. (Day 1) Pass out the Estimating the Mass of Solids Mixed with Water handout to each student. Have students read the Pre-Lesson 0.1GL Estimating the Mass of Solids Mixed with Water Handout together. This will establish the problem for students. Discuss as a class the purpose for measuring the dry mass of the plants (to measure plant growth). Discuss the steps used to calculate percentages of dry mass. Tell students that they are going to follow these steps in their lab work today. (Optional) You can show students the Measuring Plant Growth Video (https://www.youtube.com/watch?v=hVTZMLnhrJQ). 4. (Day 1) Tell students that today they will practice finding the dry mass of mixtures. This will help prepare students to find the dry mass of the materials they will use to plant their radish seeds in Pre-Activity 0.2 as well as to make calculations in Lesson 4 to prepare for explaining biosynthesis. Pass out one copy of Pre-Lesson 0.1GL Measuring the Mass of Solids in Mixtures Worksheet to each student. Show students slide 3 of Pre-Lesson 0.1GL Measuring the Mass of Solids in Mixtures PPT. Discuss the two methods for determining the mass of a solid in a mixture. 5. (Day 1) Part A Using the worksheet and the PPT, walk through the steps together in order to find the dry mass of the solids before mixing them with water. Show students slide 4 of the PPT. If students are working in pairs, have them label the bowls for each of their materials as well as with their names. Measure the masses of the 2 bowls you will use for the sponge and salt mixtures. Add the solids to the bowls. Have students subtract the mass of the bowls and enter the masses of the solids in the first column of the table in Part C of their worksheets. Add water to each bowl. Have students subtract the mass of the bowls and enter the masses of the mixtures in the second column of the table in Part C of their worksheets. Note: The row for the gel crystals in Table C will be filled in on day 2 when you hydrate the gel crystals together as a class. 6. (Day 1) Part B Using the worksheet and the PPT, walk through the steps together in order to find the dry mass of the solids after removing the water. Show students slide 5 of the PPT. If students are working in pairs, have them label the glass Petri dishes for each of their materials as well as with their names. Measure the masses of the three glass Petri dishes Add the solid/water mixtures to the Petri dishes. Have students subtract the mass of the Petri dishes and enter the masses of the mixtures in the second column of the table in Part C of their worksheets. Cut the carrots into thin strips so that they will dry more quickly and thoroughly. 7. Allow the mixtures to dry over several days or in an oven overnight. Leave the mixtures in a visible place in the classroom, and allow them to dry over several days. Alternatively, place the mixtures in a low-heated oven (<200 degrees) and allow them to dry over several hours. Caution: plastic petri dishes may melt in an oven! 8. (Day 2) Parts B and C Finish the steps in the worksheet and Slide 6 of the PPT to calculate the percentage of the mixtures that are solids. Note that when dehydrated, 1 teaspoon of Ionic Grow (out of the bottle) with a mass of 4.22 liquid grams is reduced to 0.14 grams of dry mass. In the Ionic Grow nutrient mixture, 4 teaspoons (17 liquid grams with 0.57 grams of dry mass) will be added to 1 gallon (3.79 L) of water, which has a mass of 3785 grams. The percentage of dry mass in this liquid mixture is 0.015%, which can be considered 0 for all calculation further on, although it is important for students to understand this magnitude of dry mass for when they later consider where the mass of their growing plants could have come from. 9. (Day 2) Part D. Have students complete Part D of the worksheet and discuss the questions on Slide 7 of the PPT. Tell students that when scientists measure plant growth, they use dry mass as an indicator of growth. 10. (Day 2) As a class, hydrate the plant gel crystals. Follow the steps in slide 8 of the PPT. If you haven’t already prepared the nutrient mixture to hydrate the gel crystals, add 4 teaspoons (~17 g) of Ionic Grow to a gallon (~3800) jug of distilled water. Measure the mass of the dry gel crystals and have students record this information in Part C of the Worksheet. Place the gel crystals in a large bowl and pour the nutrient mixture on top of the crystals. Tell students to record the mass of the solid water mixture in Part C (crystals + gallon water + Ionic Grow) Let the crystals hydrate overnight. Ask students at this point to share their ideas on what plants need to grow. Ask students to predict whether or not plants will grow without soil in the gel. Ask students if they think the nutrient solution will explain plant growth.