Sci-ber Text - 8th Grade

Changing Matter - Kinds of Energy

Energy is the ability to cause change! Any type of activity will require some type of energy. Energy is either absorbed or emitted during a physical or chemical change.

Heat, sound, light, motion, chemical, electrical, radiation, are all examples of typs of energy. Most of the energy found on Earth is due to the influence of our sun.

Image courtesy of SOHO

Energy is always in flux meaning it is always changing from one form to another. This is an important Law of Nature called the "Law of Conservation of Energy." It has often been said that you cannot create nor destroy energy.

Identify the kind of energy given off for each of the following:

1. Using a saw to cut a piece of wood in half.
2. The explosion of a firecracker.
3. The melting of an ice cube.
4. The glow of a fluorescent light.
5. Boiling water on a stove.
6. Dropping a glass beaker onto the floor.

Check your answers by highlighting the box below.

1. Heat, 2. Sound, 3. Heat, 4. Light, 5. Heat, 6. Sound

Now to demonstrate the relationship between changes and energy.

Materials:

500 ml. beaker
Thermometer
Ice
Salt
Balance scale
Spoon
Clock, watch, or stopwatch

Procedure:

Place the thermometer into the beaker.
Fill the beaker half-full of ice.
Use the thermometer to measure the ice temperature (make sure you wait until the temperature is stable.)
Measure 25 grams of salt and use the spoon to stir it into the ice.
Observe and record the temperature every minute. Stir the ice/salt mixture between temperature readings.
Continue the experiment for 15 minutes.

Sample Data Table:

Ice temperature at the biginning (step 3)
First Temperature reading of ice/salt mixture:
Temperature of ice/salt mixture each minute
1 Minutes after first reading of ice/salt mixture:
2 Minutes after first reading of ice/salt mixture:
3 Minutes after first reading of ice/salt mixture:
4 Minutes after first reading of ice/salt mixture:
5 Minutes after first reading of ice/salt mixture:
6 Minutes after first reading of ice/salt mixture:
7 Minutes after first reading of ice/salt mixture:
8 Minutes after first reading of ice/salt mixture:
9 Minutes after first reading of ice/salt mixture:
10 Minutes after first reading of ice/salt mixture:
11 Minutes after first reading of ice/salt mixture:
12 Minutes after first reading of ice/salt mixture:
13 Minutes after first reading of ice/salt mixture:
14 Minutes after first reading of ice/salt mixture:
15 Minutes after first reading of ice/salt mixture:

Safety concerns: Be sure to follow all glassware, and chemical safety rules that are specified by your teacher in all general laboratory experiences. As with all science lab activities, the most important safety rule is to follow all teacher directions.

Analysis:

Which kind of energy did you demonstrate was involved in this experiment?
Which purpose did the salt have in the experiment?
How could you modify this experiment to change the results?
What evidence do you have that a change occured?