Relevancy and Engagement massachusetts.agclassroom.org

One in a Million

Grade Level
9 - 12
Purpose

In this lesson, students will learn about solutes and solvents and will use serial dilution while investigating parts per million—a term used to describe the nutrient concentration of a fertilizer solution. Grades 9-12

Estimated Time
60 minutes
Materials Needed

Engage:

Activity 1: Introduction

  • Two 250 ml beakers
  • Water
  • 2 Tbs salt
  • 2 Tbs sand

Activity 2: Parts Per Million

Essential Files
Vocabulary

concentration: the ratio of the mass or volume of a substance (solute) to the mass or volume of the solvent or solution

mixture: combination of two or more different substances that are not chemically bonded and can be a solid, liquid, or gas

parts per million (ppm): a unit of measurement commonly used to describe the nutrient concentration in fertilizer solutions; can also be used to analyze contaminants in food, groundwater, air, and more; compare to one drop of water in a swimming pool

solute: the substance dissolved in a solvent to form a solution

solution: a type of homogeneous mixture in which the particles of one or more substances (the solute) are distributed uniformly throughout another substance (the solvent)

Background Agricultural Connections

This lesson is of a series called Chemistry, Fertilizers, and the Environment. These lessons introduce students to chemistry and environmental science concepts. Activities are modeled after real-life challenges that modern farmers face while producing our food, fiber, and fuel. Labs are inquiry based and promote critical thinking skills. Other related lessons include:

Fertilizers are used to provide nutrients that are not present in soil in amounts necessary to meet the needs of the growing crop. Plants can tolerate a wide range of watering and nutritional conditions, but for a commercial farming operation it is important to maximize production while minimizing environmental impact. Optimum watering and nutritional conditions vary depending on a variety of factors, including plant species, stage of life cycle, climate, and environmental conditions. Many growers purchase fertilizer, which is a solute, in a concentrated solid or liquid form. The fertilizer is then mixed with water to create a fertilizer solution that can be applied to plants.

When fertilizer is applied in the field, farmers will calculate nutrient requirements in pounds per acre. However, in greenhouse production, the industry standard is parts per million. Greenhouses are often used for growing flowers, vegetables, fruits, and transplants. Greenhouses allow for greater control over the growing environment of plants. Depending upon the type of greenhouse, key factors which may be controlled include temperature, light, water, fertilizer, and atmosphere.

Proper fertilization of greenhouse plants is essential for producing a high-quality crop. Some nutrients (such as calcium and magnesium) may be mixed into the growing medium prior to planting, but most of the nutrients are applied after planting using water-soluble fertilizers. Fertilizer injectors are used by most growers to deliver fertilizer to plants. These devices “inject” a small quantity of concentrated fertilizer into the irrigation line so that the solution leaving the hose is diluted to the proper concentration. To ensure an adequate supply of the essential elements for plant growth, growers may apply water-soluble fertilizers at a dilute concentration on a “constant feed” basis (with every watering), or on a periodic basis at a higher concentration. Fertilizer injectors can be set at different ratios depending upon the needs of the plants. If the injector ratio in a greenhouse operation is 1:100, the injector delivers one gallon of fertilizer concentrate with every 99 gallons of water (one part out of 100 parts is concentrated fertilizer).

For more information, see Answers to Commonly Asked Questions.

Engage
  1. Show students a two-minute video highlighting the career of a greenhouse manager. 
  2. Ask your students what value a greenhouse has to plant production. Through class discussion and your explanation, help students understand that greenhouses help to optimize plant production. In a greenhouse, perfect or nearly perfect temperatures, moisture, and soil nutrients can be used to grow the best crops. Many ornamental crops are grown in greenhouses such as annual and perennial flowers. However, fruits and vegetables can also be grown in a greenhouse.
  3. Inform your students that they will be learning how farmers manage the application of fertilizer to provide adequate plant nutrients. Students will:
    • learn about solutes and solvents; and
    • use serial dilution and understand parts per million measurements.
Explore and Explain

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.
Elaborate

  • Offer an incentive for students who locate (and show you) the black sphere in the Becker Bottle.

  • Review your city’s annual water quality report. All public water systems are required to sample their source water and treated water for the presence of biological, inorganic, organic, and radioactive constituents. This report typically uses parts per million and parts per billion to summarize constituent levels. Look up and define unknown terms and summarize key findings.

  • One part per million is equivalent to one hole in 55,555 rounds of golf! Put a million into perspective by challenging students to use the factor-label method to convert one part per million (or one part per billion) to a number that is meaningful to them. Consider expressing the unit of measurement in seconds, miles, U.S. population, etc.

Evaluate

After conducting these activities, review and summarize the following key concepts:

  • A mixture is a combination of two or more different substances, which are not chemically bonded, and can be a solid, liquid, or gas.
  • If nutrients do not exist in soils, they can be added with fertilizers that are properly measured. Parts per million is a method of measuring the correct concentration.
  • Using the proper amount of fertilizer is best for the farmer and the environment.
Sources

 

Acknowledgements

This unit was funded in 2011 by the California Department of Food and Agriculture’s (CDFA) Fertilizer Research and Education Program (FREP). Chemistry, Fertilizer, and the Environment was designed to reinforce chemistry and environmental science concepts while educating students about the relationships between food, plant nutrients, farmers and the environment.

Executive Director: Judy Culbertson
Illustrator: Erik Davison
Layout and Design: Nina Danner

Recommended Companion Resources
Author
Mandi Bottoms and Shaney Emerson
Organization
California Foundation for Agriculture in the Classroom
Powered by the National Agricultural Literacy Curriculum Matrix (agclassroom.org)