Teachers TryScience

Energy from Food

Apr 20 2011

Source: MDominguez2

Summary Information

Keywords:

energy, digestion, battery, fruit, vegetable, transfer, producers, electrochemical, electron, electrode, zinc, redox reaction, anode

Topic:

Physical Science

Workplace Skills:

Raising Questions

Problem Solving

Planning investigation

Discussion

Estimated Time Required:

less than 1 hour

Target Grade (Ages):

Grade 5 (Ages 10-11)

Diversity Indicators:

Differentiation occurs and is articulated when measuring student responses and questions.

Watch this Lesson in Practice

Tab Wrapper

LESSON

Goals and Prerequisites

Goals:

In this inquiry-based lesson, we will investigate the idea of how energy is transferred from food. The potato clock will serve as an illustrated example of how chemical energy is transferred into electrical energy.

Prerequisites:

Students should have a basic understanding that plants and animals store unused energy, and when eaten human beings receive this energy. This process can be illustrated through 'seeing' the energy in vegetables and fruit as it's used to run a LCD clock.

Instructional Objective(s)

Students from grades three through five will by the end of the lesson:

Understand that all living things need energy to survive. This is usually understood as sunlight, air, water and food.
Connect nutrition with the energy flow, and that it begins in plants.
Know that the sun's energy flows through all living things.
Comprehend that energy stored in food is chemical (potential) energy.

Instructional Resources

Background:

Difficulty: Moderately Easy

When I first saw the 'potato clock,' I was actually looking for a way to show third through fifth graders how humans absorb energy from food; vegetables and fruits/plants. The clock illustrates quite nicely how chemical energy stored in the potato transfers to electrochemical energy strong enough to run the clock. Much in the same way we take in chemical energy stored in the plant, but convert it into chemical energy for our bodies, to run.

For all, there is a chemical reaction within the potato battery that causes the electrons to move. The electromotive force within each potato is the ability it carries to move electric current. In the electrochemical cell, such as the potato battery, the copper wire makes the electrons move in the potato, causing energy to move into the clock. More, the copper and the zinc (found in the galvanized nails) are called electrodes, and the potato is called an electrolyte. Fruit and other vegetables work well too. They contain plenty of particles that allow current to flow between the metal stips.

The first battery was made by Italian scientist Alessandro Volta (1745-1827). He built a pile of metal discs with card soaked in salty water between them. It produced a small electric current. This battery is known as a Voltaic pile. Copper is a great conductor of electricity. It is used to make wires and cables. Zinc is important because it used to galvanize steel objects such as garden tools and screws. The objects are coated with zinc, which protects the steel from rusting.

Before attempting this lesson, teachers should think about ways to incorporate the following topics:

The Digestive System: For elementary students, I use an internal organ vest showing the digestive and respiratory systems.
An overview of Lipid Function: I incorporate an interactive link to: http://www.wiley.com/legacy/college/boyer/04.
Terms such as nutrition, absorption, storage efficiency, metabolic changes and the caloric content of food should be defined and included in the conversation.

Materials:

Each student group will need:

2 drywall nails
3 alligator clips
Copper wire
2 galvanized nails
2 baking potatoes

Procedure:

Create student groups of three to four students. Groups will work to create the clock after you have done the demonstration or can follow you step by step during the demonstration. Alternatively, you could ask students to try to create the clock, and then you could demonstrate this procedure afterwards while leading a class discussion.
Assemble the supplies. You need two galvanized nails; three alligator clip/wire units - that is alligator clips connected to one another with wire; two short short pieces of heavy copper wire; a simple low voltage LED clock unit; and two potatoes. Obtain a simple LED clock unit that functions from the power of a 1-to 2-volt, button type battery.
Open the battery compartment and remove the battery. (Let them see you do this step,)
Note that there is a positive (+) and a negative (-) terminal point where the battery was installed.
Identify the potatoes as number one and number two.
Insert one nail in each potato.
Insert on short piece of heavy copper wire in each potato, placing it as far away from the nail as possible.
Use one alligator clip/wire to connect the copper wire inserted in potato one to the positive terminal in the clock unit.
Use the alligator clip/wire to link the nail in potato two to the negative terminal in the clock unit.
Use the final alligator clip/wire to link the nail in potato one to the copper wire in potato two.
Set your clock. You can now substitute the potatoes with other vegetables and fruits. You can even use a carbonated cola drink as a power source.

Extensions

Potato battery could provide inexpensive power for developing world (video) at http://www.huffingtonpost.com/2010/07/30potato-battery-could-prov_n_665578.html?
Find Food and Nutrition videos or interactives online that correspond to energy in food. (When you find any email me.)

Assessments and Rubrics

Example questions used during lesson include but are not limited to:

Q. What the energy that is stored in food called? (A. Chemical energy.)

Q. Where is it stored in plants? (A. It's stored in plant cells.)

Q. What is energy transfer?

Q. How are nutrients used in our body?

Q. How is energy stored in food transformed?

Q. How are calories measured in food sources?

Make connections to human digestion, circulatory and respitory systems.

External Resources

You can purchase a Potato Clock kit in a box sold commercially if you choose not to have students build their own.
Some definitions were found at www.buzzle.com.

Credits

The world wide web was an invaluable resource in the Science Lab. We don't have curricula meeting this particular need in energy transfer or absorbtion.

www.DiscoveryEducation.com
www.4M-ind.com
eHow contributer FOSS kits

RESOURCES

Original Resources

Lessons In Practice

Energy from Food Introduction

Introduction

Energy from Food Lesson

Lesson

Energy from Food Reflection

Reflection

Contributed Resources

Contribute a Resource

Designing a High Voltage Potato

Worksheet for high school students performing this lab

TV411 Carbohydrates

TV411 Heat

STANDARDS/CURRICULUM

Add Standards/Curriculum

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Your Rating:

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Comments

Not yet Nicole, I cant find

Not yet Nicole, I cant find large enough potatoes, maybe we can use a whole bag at once. :)

Diid this lesson with high school biology students

I did this lesson with my high school biology students. It was very easy to set up once I knew what I needed. I connected the copper wire and the nail with alligator clips to a multimeter and students experimented with different substances (raw and cooked potatoes, lemons and soda) to see what combination would give them the highest voltage. They were very engaged and enjoyed the opportunity to engineer something in class. I discussed how the potatoes caused a chemical reaction with the zinc which caused the electrons to flow...and how the flow of electrons transfers energy. I tied this in to the flow of electrons in the mitochondria and chloroplast. This lesson would also be great for kids in chemistry, physics or just a basic lab science class.

Much misinformation and

Much misinformation and inaccurate statements in this lesson plan.
1. The electrical energy that this apparatus produces does NOT come from the potato! The energy comes from electron transfer between the copper and zinc. Prove this by using salt water or vinegar instead of the potato. The voltage produced will be the same.
2. More proof - a zero calorie carbonated drink will work as well a one with sugar.
3. Energy is NOT absorbed from food. Energy is obtained from food through metabolic processes which oxidize fats, protein and carbohydrates. A much better analogy to demonstrate this is to set on fire a dry cracker, a dry piece of spaghetti or a nut. The food burns producing light and heat energy through oxidation.
4. "The electromotive force within each potato is the ability it carries to move electric current." This sentence is nonsense and completely wrong.
5. The potato is not an electrolyte. An electrolyte is a solution of ions. The fluid in the potato is an electrolyte.
6. This lesson should be part of a unit on electricity. Teaching it in conjunction with food makes no sense and will greatly use the children. Obviously the teacher is completely confused.
I have a degree in Biology with a minor in chemistry.

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