Activity 1: Introduction

1. Ask the class if they have ever used a powdered concentrate to create a beverage, such as hot chocolate or fruit punch. Explain that whether they realized it or not, they were creating a mixture. A mixture is a combination of two or more different substances, which are not chemically bonded, and can be a solid, liquid, or gas. Explain that there are two types of mixtures: homogeneous (also called solutions) which are uniform and particles are not typically seen, and heterogeneous mixtures which are not uniform and in which the particles can be seen.
2. As a demonstration, add two tablespoons of salt to a 250 ml beaker of water and stir. Explain that the mixture is a homogeneous solution, meaning that the molecules within the solution, in this case water and table salt, are evenly distributed and look the same throughout.
3. Add two tablespoons of sand to a 250 ml beaker of water and stir. Have students compare and contrast the two mixtures. Ask students to describe the difference between the sand and water mixture and the salt and water mixture. Explain that the sand and water mixture is a heterogeneous mixture, meaning that the molecules will not be evenly distributed throughout the liquid.
4. Explain that in agriculture, fertilizer solutions are one way that farmers supply their crops with essential plant nutrients. In science terms, the solute is the fertilizer added to the water. The water is the solvent, which does the dissolving. The solution more or less takes on the characteristics of the solvent. The concentration of a fertilizer solution is defined by the amount of fertilizer (solute) dissolved in water (solvent).

Activity 2: Parts Per Million

1. Ask students to raise their hands if they’ve ever heard the term “one in a million.” Discuss what the term means and why people say it.
2. (Optional) Build on the classroom discussion by explaining how unique “one in a million” really is. Show students a “One in a Million” Becker Bottle to illustrate the concept. This three liter bottle contains one million tiny colored spheres. Each colored sphere represents a different quantity, or concentration. The yellow spheres represent 100,000 in a million, the red spheres represent 10,000 in a million, the white spheres represent 1,000 in a million, the pink spheres represent 100 in a million, and the green spheres represent 10 in a million. The single black sphere in the bottle represents one in a million, or in scientific terms, one part per million. Explain that today the class is going to investigate the scientific concept of “parts per million”—a unit of measurement used to describe a very small amount of material.
3. Explain that in the scientific community, parts per million is expressed as “ppm.” Parts per million is the unit of measurement commonly used to describe the nutrient concentration in a fertilizer solution. It can also be used to analyze contaminants in food, groundwater, air, and more.
4. Introduce the lab by explaining that students will use a dilution activity to create and investigate solution concentrations. Review laboratory safety instructions.
5. Give each student one copy of the One in a Million lab sheets. Note that pages 1-2 contain the lab instructions and pages 3-5 ;are where students will record the data.
6. Divide the class into pairs or triads, and provide the following lab materials for each group:
   • One white ice cube tray (or well reaction plate with 12 wells)
   • One permanent marker
   • One eye dropper
   • One 1 liter beaker
   • Three small plastic cups
   • Food coloring, any color except yellow
   • Colored Pencils or crayons
   • Water
7. Review the lab with students and answer questions as needed.
8. After students complete the dilution lab activity and the One in a Million lab worksheet, use a classroom discussion to debrief their findings. Discussion points may include:
   • Good fertilizer practices that match fertilizer inputs to crop nutrient requirements will achieve high-quality, economically sustainable yields and will protect the environment. Arable land available for growing food will continue to diminish as population growth continues. Efficiently managing inputs, such as water and fertilizer, will be essential to feeding a growing population.
   • Improperly applied fertilizer can lead to environmental problems. It is important for anyone who applies fertilizer to follow application instructions. Farmers and researchers are constantly testing and implementing new methods for high precision use of fertilizers.
   • Fertilizer is expensive. It is in the farmer’s best interest to apply the correct amount of fertilizer, supplying the plants with only the nutrients they need.

ELL Adaptations

• Create a Venn diagram to capture the differences and similarities of homogeneous and heterogeneous mixtures.
• Use an overhead projector to demonstrate complex math problems.