Students investigate the transfer of energy in the process of making milk, discover that there are different forms of energy, determine that living things need energy to survive, and identify the sun as the primary source of energy. Grades 3-5

energy: power derived from the utilization of physical or chemical resources

kinetic energy: the energy of motion

photosynthesis: the process by which plants convert carbon dioxide, water, and light energy into sugars and oxygen in order to store energy; the opposite of cell respiration

This lesson is part of a series called, Milk Matters: Discovering Dairy. These lessons introduce students to the history, production, nutritional value, and economic significance of the dairy industry. Other related lessons include:

• Cowabunga! All About Breeds 
• Sun, to Moo, to You!
• Milk Makin' Math
• The Ultimate Efficient Recycler
• A Day Without Dairy

In this lesson, students will discover how the process of making milk involves energy transfer from the sun to dairy cows and finally, to the consumer. Students will understand the difference between chemical, radiant, and kinetic energy and that all living things need energy to survive.

Humans and animals get their energy from nutrients produced by plants. Humans and dairy cows can both receive energy from plants in the form of fruits, vegetables, or grains. All of the energy in nutrients originally comes from the sun.

Plants absorb the sun’s radiant energy and transform it into chemical energy through the process of photosynthesis. The plants use much of this energy to grow and store the remaining energy in their cells. When dairy cows eat feed, such as alfalfa, they are able to use the chemical energy stored in the plants they consume. Dairy cows use this energy to do everything from eating and digesting their food to breathing and producing milk. The milk produced by dairy cows also contains part of this energy. When we drink milk or eat products made with milk, we receive the energy that originally came from the sun. Our bodies rely on kinetic (physical) energy to do work, have fun, and accomplish tasks.

More background information on the dairy industry can be found here.

1. Ask students, "What is energy?" Allow students to offer answers using their background knowledge.  
2. Ask students further questions to help them identify when energy is required and that it is transferred through cycles. Questions could include, "What activities require energy?" "Where do you get energy?"
3. In this lesson, students will:
   • investigate the transfer of energy in the process of making milk;
   • demonstrate how energy can be lost during energy transfer; and
   • identify the many ways humans and cows use energy.

Activity 1: The Journey of Milk

1. Ask the students to think of their favorite sport. How would they feel if they played in the championship game of this sport and had not had anything to eat? Pair students up and have them share their responses with their partner.
2. Survey the class for different responses. How many said tired, sick, or grumpy? Brainstorm with the students why they might feel tired. Ask how they would feel if, after the game, you offered them a nice, cold glass of… hay?! Show the students a glass full of hay or grass. Explain that dairy cows convert the feed they eat into the milk we consume on a daily basis. Energy plays an important role in this process.
3. Show the students The Journey of Milk, a video about the process of making milk. Instruct the students to look for how dairy cows use and consume energy at each step of production.
4. Discuss the video with the students and work as a class to construct a production timeline on the board. Explain that in each of these steps, energy transfers. In a moment, they will go outside to see how energy moves between objects and people.
5. Take the students outside. Organize the students into groups of four and provide each group with a bouncing ball. Instruct the students to pass the ball between their group members in a variety of patterns. The teacher determines the patterns and may wish to blow a whistle to get the students’ attention in changing patterns. Possible pattern ideas include bounce pass-chest pass, skipping every other person, increasing the number of bounces with each pass, passing the ball clockwise vs. counter-clockwise, etc.
6. Take the students inside the classroom to debrief the activity. Ideas for discussion:
   • Use student volunteers to demonstrate how we use kinetic energy to pass the ball.
   • Use student volunteers to demonstrate how we absorb kinetic energy when we catch the ball.
   • What happens to energy when the ball bounces?
   • What happens to the ball when it is windy outside?
   • What happens if you bounce a ball on grass? A basketball court?
7. Explain that just as we used energy to pass the ball, we use energy to do many other things in our daily lives as well. Distribute the Using Energy activity sheet. Instruct the students to first identify and label ways our bodies use energy.
8. Next, they will identify and label how dairy cows use energy. Focus on the energy dairy cows use to create milk. Ask the students to share with a partner where the energy comes from and where it goes when cows create milk. Have the partners share with entire class.
9. Briefly, review the timeline created at the beginning of the lesson and review how energy moves between each step of the process.

Activity 2: Relay Race 

1. In preparation for this activity, copy the Sun, to Moo, to You Relay Cards onto 3-5 different colored sheets of cardstock. Cut each card out, creating a set of relay cards for 3-5 different teams.
2. Divide the students into teams of seven students. Teams without seven students will need to select one or more members to complete the relay twice.
3. Assign each team a color based on the color of their Sun, to Moo, to You Relay Cards. Outside, the students line up with their teams in single file lines. Five yards in front of each team’s starting line, place a jump rope. Several feet beyond the jump rope, spread out the team’s relay cards face down. Five yards further, place a finish line.
4. Explain to the students that they are about to participate in a relay race team competition. Build up the importance of supporting each other and contributing to the goals of the team. Demonstrate how each student will individually leave his or her team’s starting line. They will run to the jump rope and jump rope five times. Next, they will pick up one of the seven relay cards and run to the finish line. Once they are at the finish line, they will yell, “Moo!” to signal the next teammate in line to begin the relay.
5. Once the entire team has crossed the finish line, the team members will work together to put each of the relay cards in the correct order. The cards will create a sequence showing how energy moves within the process of making milk. When the team has completed the entire relay, team members must all sit quietly in a line. The first team sitting quietly on the grass wins! The winning group reviews the correct order with the class.

Variations

• Play kickball, baseball, or another team sport to observe the loss and gain of kinetic energy.
• Take the students on a field trip to a dairy to see the actual process of milk production.
• Ask a local dairyman to visit your class as a guest speaker.
• Instead of completing the Using Energy activity sheet, instruct the students to draw a picture of themselves engaged in a daily activity.
• Ask the students to identify and label ten ways they are using energy in the picture.

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

• Dairy cattle produce milk. Milk and other dairy products, such as yogurt and cheese, are a healthy source of protein to our diet.
• All energy is originally derived from the sun.
• Plants produce energy through photosynthesis and cattle eat plants such as grass, hay, and grain. Cattle convert the plant energy into producing milk which provides healthy foods for our diet. (From the sun, to moo, to you)

This lesson was funded in 2008 by the California Milk Advisory Board and the California Farm Bureau Federation. To meet the needs of California educators, Milk Matters: Discovering Dairy was created to meet the Curriculum Content Standards for California Public Schools. The unit also includes a collection of relevant resources about the dairy industry.

Executive Director: Judy Culbertson
Layout and Design: Imelda Muziom

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