CONTENT STANDARDS: Physical Science

GRADE: Seventh

CONTENT STANDARDS: Physical Science

CONTENT TOPIC: Transformations of Energy

CONCEPT: Matter and energy in the universe are governed by physical law.

CONTENT OBJECTIVE: 7C1.00 To understand the relationship between energy and matter

INSTRUCTIONAL OBJECTIVES: The learner will:

1.01 define the term mass.
1.02 demonstrate an understanding of mass by correctly measuring various objects using a balance.
1.03 define the term energy.
1.04 define potential energy and give an example.
1.05 define kinetic energy and give an example.

I. Mass
A. Definition
B. Measurement
1. Instrument
2. Unit
II. Energy
A. Potential energy
1. definition
2. examples
B. Kinetic energy
1. definition
2. examples
III. E=mc²
A. Statement of law
B. Developed by Einstein
C. Relationship of matter and energy

TN COMPONENT OF SCIENCE: Process Of Science

TN GOAL:

To enable students to demonstrate the process of science by posing questions and investigating phenomena through language, methods and instruments of science

1.4 ANALYZING - Data should be examined to find patterns and relationships that may suggest cause and effect or support inferences and hypotheses.

1.4a Data should be examined to find patterns and relationships.

BENCHMARK: An equation containing a variable may be true for just one value of the variable.

TIME REQUIRED:

45-50 minutes

Triple-beam balance, various objects to measure such as glass, nail, chalk, pen, graduated cylinder

All of us have a certain amount of material making up our body; this is our mass. Today we are going to learn about mass and measure the mass of various objects. We will also see how this mass relates to energy.

All objects have a certain amount of material in them; this material is the object's mass. Mass is constant; it never changes with location or temperature. Mass is measured on a special piece of equipment called a balance. It is generally measured in a special unit called a gram.

Energy is the ability to do work. Work is done when objects with mass are moved some distance. You can push on a tree all day but unless the tree moves, you have done no work. Lifting a box is an example of work. Can you name other examples of work? (Be sure the students name moving an object some distance.)

There are two special categories of energy. The first is potential energy. Potential energy is stored energy or energy an object has because of its position. To have potential energy an object must be raised above the surface of the earth. An example of potential energy is a book lying on a table. The book is raised above the surface of earth, so it has potential energy. The second type of energy is kinetic energy, which is energy of motion. To have kinetic energy, and object with mass must have a speed that it is moving. An example of kinetic energy is the energy that is possessed by a thrown baseball.

Einstein found that matter and energy were related in a special equation, E = mc². This equation means that matter is not destroyed in a reaction, but is converted to energy. Likewise, energy is not destroyed in a reaction, but is converted to matter. This equation is important because it relates matter and energy.

1. (If your department does not have a pan balance or triple beam balance, you might borrow one from your high school. Most chemistry departments should have a balance.)

Divide the class into small groups of two or three and let them take turns, if necessary, finding the mass of several objects. Use heavy objects such as a glass or beaker, eraser, scissors, and small objects such as a pencil, pen, or graduated cylinder. After all groups have measured the objects, have them compare their findings. Help them to see that larger objects generally have more mass while smaller objects have less mass. (You might also point out that it requires more energy to move the larger objects than it does to move the smaller objects.)

2. (If you have accelerated students, give them a worksheet of problems to solve for potential and kinetic energy using the formulas PE = mgh (where g is the acceleration due to gravity = 9.8 m/s²) and KE = 1/2mv².)

(Discuss with students the concept of energy conversion. An example in point - A 10 kilogram rock at the top of a cliff 100 meters high has potential energy.

PE = mgh
= 10 kilograms x 9.8 m/s² x 100 meters
= 9800 Joules (the unit for energy)

As the rock falls, the PE is converted to kinetic energy. Halfway down, one half of the PE or 4,900J has been converted to KE.

PE = 1/2mv²
PE =l/2 x l0Kg x (31.3m)²
PE = 4900J

PE =mgh
PE = 10kg x 9.8 m/s² x 50 m
PE = 4900J

At the bottom of the cliff, all the PE has been converted to KE the instant before it hits the ground.)

Have the students classify the following as examples of potential energy or kinetic energy:

1. a bird sitting in a tree (PE)

2. a bird flying through the air (KE)

3. a book falling off a disk (KE)

4. roller coaster (KE)

5. a chicken on a barn roof (PE)

Today we have learned how to measure an object's mass and how its mass is related to energy. Turn to your neighbor and tell him the two types of energy and the definition of each type.

energy - ability to do work

gram - metric unit for measuring mass

kinetic energy - energy of motion

mass - the amount of material in an object

potential energy - stored energy or energy of position

This is the time this file has been accessed since 04/02/98.

The University of Tennessee at Martin is not responsible for the information or views expressed here.

Seventh Grade Science Home Page

Last Modified