Investigation Sequence


Limits to Energy Sources

Written by:

adapted from: Bybee, Peterson, Bowyer, and Butts. Science and society/activities. Charles E. Merrill Publishing Co. A Bell & Howell Company                 Date 1994

Focus Questions

Can energy use be reduced?
Can certain types of energy use be reduced?


Content: Earth, Physical, & Life

Sources of energy are limited.
Some sources can only be used once.
Conservation is one method of using less energy. Conservation is using less. Conservation is the preservation of resources through decreased use.
Changing energy sources is one method of reducing the use of certain kinds of energy.
Some energy sources are more abundant than others.
Depletion of resources can only be stopped by 1. decreased use and 2. increased supply.

Cross cutting concepts

Energy transfer causes a change, but those changes have some constancy.
Transfer of energy will occure until there is equilibrium.

Science Practice

Observational data can be used to explain ideas and answer questions.

Personal, Social, Technology, Nature of Science, History

Technology can be created using scientific ideas.

Background information

Energy resources can be grouped as nonrenewable, renewable, and synthesized.

The limit of a nonrenewable resource is the amount of that resource that can be found and used at a reasonable cost and marginal environmental impact.

In short, it is the quantity of the resource that defines the limits to its use. By analogy using a nonrenewable resource is like living off your savings when you have no income. When the savings is gone, your income is gone.

Renewable resources are, in theory, limitless. But in fact, there is a limit. If a renewable resource is used faster than it can be replenished, then the resource becomes depleted and ultimately is nonrenewable. Again, by analogy, using renewable resources is like living off the interest of your savings without using the capital. If use exceeds the interest rate, then capital is diminished at your rate of expenditure until your capital is depleted. In the case of a renewable resources it is the rate of use that is the limiting factor.

Energy must be available in useful form, at reasonable costs and without harmful effects on the environment. Energy scarcity, then, does not really mean we are running out of energy sources. It means that there may be a shortage of a resource, a rise in price (such as happened in the OPEC price increases) or a substantial amount of environmental damage.

Societal implications
Oil and gasoline prices have risen since 1973. The oil embargo made individuals aware of another fact--the dependency of other social factors on petroleum. Energy is needed for much more than cars. Energy is needed to run machines and grow food; and, if the source of energy is oil and it becomes more expensive, so does all the products for which oil is a source of energy.
1973 was a turning point for industrialized countries. During the period from 1973 to 1980 we became aware of the limits to our energy resources. If we take the lesson of limits seriously and start the transition to conservative practices and alternative sources, all will be well. If, on the other hand, we do not face the reality of limited energy resources, our society will be in serious trouble.

Activity Sequence

Exploration Activity - Activity 1

Invention Activities - Activity 2

Expansion Activity

Activity Descriptions

Activity 1

Small birthday candles, matches, styrofoam cups, clock, thermometer, test tubes, and test tube holder for each group of students.

1. Before class place a small hole in the bottom of the styrofoam cup. Then place the candle in the bottom of the cup to make a candle holder.
2. Distribute the materials to each group of students.
3. Tell the students they are going to use the candle to heat water in their test tube.
4. Place 5 cm of water at room temperature in their test tube.
5. Tell the students they are to heat the water and increase the temperature by 10 degrees C. During the activity they should record: (1) How long it takes to heat the water 10 degrees C. (2) How much (in centimeters) of their candle is used.
6. Discuss their results when they have completed the activity. During the discussion ask them: How long do they think it would have taken to heat the water 20 degrees C, 30 degrees C? How long would your candle last?

Activity 2

1. The second part of this activity is a challenge. Challenge the students to heat their water 30 degrees C without using all of their candle. Tell them to record what they do and the results they obtain.
2. Have the students share their results with the rest of the class.
3. During the discussion list their ideas on the overhead or chalkboard and classify them according to those that represent conservation of the energy source and those that represent use of other energy sources and combinations of the conservation and use of renewable resources.
4. Extend the discussion to the limits and conservation of natural resources such as fossil fuels.
5. Have the students design their own activity to demonstrate more efficient methods to use energy.

Dr. Robert Sweetland's notes