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Plants | Pre-Lesson Activity 0.1GL

Pre-Activity 0.1GL: Keeping Track of Solids in Mixtures (60 min + overnight or several days)

Students will practice measuring the mass of solids in two different ways: before making a mixture and after taking water out of a mixture. This will set them up to make more precise calculations of dry mass on their individual plants.

This Pre-Lesson Activity is part of the Gel Protocol (2–turtle) and should only be taught if you have chosen this pathway (see Background Information for details).

Materials You Provide

You can do the investigation with students collecting their own data or with data coming from whole class demonstrations. Materials lists for each are below.

For whole-class demonstrations:

  • Calculators (1 per pair of students)
  • Dry sponge
  • Salt (about 100 g)
  • Dry plant gel crystals (1 packet per class)
  • Baby carrot
  • Salt water mixture (about 10 g of salt in 50 ml of water)
  • Ionic Grow (4 teaspoons, about 17 g; plus an additional 4 teaspoons to make a mixture, see Setup below)
  • Distilled Water (1 gallon per class)
  • Glass Petri dishes (3)
  • Digital Scale
  • Scissors or knife
  • Strainer/colander large enough for hydrated gel (1 per class)
  • Bucket or bowl (>1 gallon) to hydrate gel overnight (1 per class)

For students working in pairs:

  • Dry sponge (1 per pair of students)
  • Salt (1t per pair of students)
  • Dry plant gel crystals (1 packet per class)
  • Baby carrot (1 per pair of students)
  • Salt water mixture (about 1 cup of salt in 4 cups of water)
  • Ionic Grow (1t per pair of students; plus an additional 4 teaspoons to make a mixture, see Setup below)
  • Distilled Water (1 gallon per class)
  • Small bowls, preferably transparent (3 per pair of students)
  • Petri dish (3 per pair of students)
  • Digital Scale (1 per pair of students)
  • Calculator (1 per pair of students)
  • Scissors or knife (1 per pair of students)
  • Tape and marking pens (enough for container labels)
  • Strainer/colander large enough for hydrated gel (1 per class)
  • Bucket or bowl (>1 gallon) to hydrate gel overnight (1 per class)

Resources Provided

Setup

Setting up Part A:

Prepare three small bowls for making the mixtures with the sponge, salt, and gel crystals. Prepare tape and marking pens to label the bowls.

Setting up Part B:

  • If using a warm oven, prepare 3 glass petri dishes, or other small ovenproof containers, per pair of students for drying the mixtures. If not using an oven, prepare 3 petri dishes per pair of students for drying the mixtures and a space in the classroom for the mixtures to sit out for several days until dried. If using an oven, prepare marking pens to label the containers. If not using an oven, you may also prepare tape to label the containers.
  • Prepare a mixture of salt and water, enough to have about 1 teaspoon of mixture for each class.
  • Prepare a pair of scissors or a knife per pair of students to cut the carrots into thin strips.

Setting up for Pre-Activity 0.2GL:

  • Prepare the Ionic Grow mixture, either ahead of time, or during the Activity with students. Add 4 teaspoons of Ionic Grow mixture to a jug. Then add enough distilled water so the final volume is 1 gallon. This is the nutrient mixture that will hydrate the gel.
  • You will be hydrating the gel crystals to prepare them for planting the radish seeds in Pre-Activity 0.2GL. One package, or ~17 g of plant gel crystals absorbs about 1190 g of nutrient mixture to make about 1200 g of hydrated gel (enough to fill ~60 37mL test tubes). Instructions for hydrating the gel are included in the Directions in this Pre-Activity. You will hydrate the gel with the Ionic Grow mixture. Note that the above are mass approximations, and the mass of your packet of gel crystals as well as the mass of the nutrient mixture it absorbs may be slightly different than our estimations.

Print one copy of Pre-Lesson 0.1GL Measuring the Mass of Solids in Mixtures Worksheet and Pre-Lesson 0.1GL Estimating the Mass of Solids Mixed with Water Handout for each student. Prepare a computer and projector to display Pre-Lesson 0.1GL Measuring the Mass of Solids in Mixtures PPT.

Directions

1. Use the instructional model to show students where they are in the course of the unit.

Assessment

During the demonstration, note how students express their ideas about the difference between mass and dry mass or solid mass.

Tips

  • When possible, lead the demonstrations in such a way that students can see what you are doing. Make use of a document camera, move classroom furniture around, position students strategically, elicit student volunteers to help with different steps, etc.
  • Don’t forget to carefully model for students how to account for the tare of the container when measuring the mass of the solids and mixtures.
Differentiation
Modifications
Extending the Learning