Key Idea: Regardless of what happens within a system, the total amount of energy in the system remains the same unless energy is added to or released from the system.

Students should know that:

  1. Regardless of what happens within a system, the total amount of energy in the system remains the same unless energy is added to or released from the system, even though the forms of energy present may change.
  2. If the total amount of energy in a system seems to decrease or increase, energy must have gone somewhere or come from somewhere outside the system.
  3. If no energy enters or leaves a system, a decrease of one form of energy by a certain amount within the system must be balanced by an increase of another form of energy by that same amount within the system (or a net increase of multiple forms of energy by that same amount). Similarly, an increase of one form of energy by a certain amount within a system must be balanced by a decrease of another form of energy by that same amount within the system (or a net decrease of multiple forms of energy by that same amount).
  4. Energy can neither be created nor destroyed but it can be transferred and/or transformed.
  5. If energy is transferred to or from a very large system (or a very complex system), increases or decreases of energy may be difficult to detect and, therefore, it may appear that energy was not conserved.

Boundaries:

  1. Students are not expected to quantitatively keep track of changes of energy in a system.
  2. Assessment items will avoid using the phrase “energy conservation” or “conservation of energy” because of the misconceptions associated with them (see list of misconceptions).
  3. Students are not expected to know about energy-mass conversions such as nuclear reactions or other subatomic interactions.
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number
Knowledge Being Assessed Grades
6–8
Grades
9–12
Select This Item for My Item Bank

NG083003

Energy is transferred to the air around hot food as the food cools even though the temperature of the air does not appear to increase.

53%

59%

NG071002

Assuming that no energy is transferred between a ball and the curved track it is moving in, or between the ball and the air around it, the ball will move down the track and then up to a point equal to the height from which it started.

51%

55%

NG084002

Assuming that no energy is transferred between a ball and the curved track it is moving in, or between the ball and the air around it, the ball will only move to a height equal to the height from which it started. It will not be able to go over a hill that is higher than the point from which it started.

48%

53%

NG085002

Assuming that no energy is transferred between a ball and the curved track it is moving in, or between the ball and the air around it, the ball will not have enough energy to go over a hill that is higher than the height from which it started because the total energy of the system has to remain the same.

39%

51%

NG075003

Assuming that no energy is transferred between a ball and the curved track it is moving in, or between the ball and the air around it, a ball on a curved track will reach a point as high as the point from which it started because as the ball moves down the track, its gravitational potential energy will change into motion energy, and as the ball goes up the other side, its motion energy will be changed back into an equal amount of gravitational potential energy.

36%

44%

NG070002

Assuming that no energy is transferred between a ball and the curved track it is moving in, or between the ball and the air around it, the ball will move to a height equal to the height from which it started.

32%

44%

NG088003

When a student shoots a rubber band across the room, the elastic energy of the rubber band is transformed into motion energy, and the total amount of energy stays the same. (This item uses bar graphs to depict the amount of each kind of energy.)

32%

44%

NG089003

The total amount of energy in a lunch box containing only an ice pack and the air around it remains the same even after the ice pack gets warmer and the air gets colder. (This item uses bar graphs to depict the amounts of each form of energy.)

30%

38%

NG081003

The total energy inside a closed cooler filled with ice and a can of soda stays the same even though the can of soda gets colder, because the amount of energy that the can of soda lost is equal to the amount of energy that the ice gained.

27%

42%

NG080003

As a clay ball falls and hits the ground, the total amount of energy in the system stays the same because the decrease in energy due to the clay ball moving closer to the ground is equal to the increase in energy due to the clay ball and the floor getting warmer.

26%

38%

NG096002

The total amount of energy a ball has does not change after it goes down and up a dip because the total energy of the system (ball and track) does not change (assuming no energy transfer between the ball and the track and the ball and the air around it).

24%

38%

NG078002

After a rubber band is used to shoot a toy car across the floor, the total energy of the system will remain the same because the increase in the motion energy (kinetic energy) of the car is the same as the decrease in the elastic energy of the rubber band.

23%

33%

NG095002

The total amount of energy a ball has does not change after it goes down and up a dip because the total energy of the system (ball and track) does not change (assuming no energy transfer between the ball and the track and the ball and the air around it).

22%

34%

NG065004

A pendulum stops swinging because the motion energy of the ball is transferred somewhere else, like the air, as the ball swings from side to side.

20%

32%

NG094002

Assuming no energy transfer between a ball and the track it is moving in, the amount of energy the ball has after it goes over a hill will be the same as before it went over the hill because the total amount of energy in the system did not change.

18%

31%

NG092002

Assuming no energy transfer between a ball and the track it is moving in, the amount of energy the ball has after it goes over a hill will be the same as before it went over the hill.

18%

27%

NG086002

Assuming no energy transfer between a roller coaster car and the track it is moving in or between the car and the air around it, all of the hills that a roller coaster car can get over must be lower than the height of the starting point.

19%

25%

NG090002

Assuming no energy transfer between a ball and the track it is moving in, the speed of the ball will be the same before and after rolling over a hill because the total amount of energy in the system does not change.

12%

18%

Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

EGM035

Springs or other elastic objects have the same amount of elastic energy regardless of how much they are stretched or compressed (AAAS Project 2061, n.d.).

39%

30%

NGM010

Energy can be created (Kruger, 1990; Lovrude, 2004; Papadouris et al., 2008).

33%

28%

NGM009

An object has energy within it that is used up as the object moves (Brook & Driver, 1984; Kesidou & Duit, 1993; Loverude, 2004; Stead, 1980).

31%

29%

NGM043

For a ball traveling over a frictionless hill, the steepness of the path is the most important factor affecting the ball’s speed and motion energy (Duit, 1981).

31%

27%

NGM044

For a ball traveling over a frictionless hill, the length of the path is the most important factor affecting the ball’s speed and motion energy (Duit, 1981).

28%

23%

NGM037

An object always gains energy as it moves. For example, the height that a pendulum reaches after it is released is greater than its starting height because it gains energy as it swings (Loverude, 2004).

24%

22%

NGM060

Energy can be destroyed (Kruger, 1990; Trumper, 1998).

22%

19%

EGM048

Living things give inanimate objects energy by carrying or pushing them. For example, a person gives a bike energy by riding it or a bird give a stick energy by carrying it (Herrmann-Abell & DeBoer, 2010).

17%

13%

NGM045

Hills are speed booster, which means that the speed of a ball after rolling over a hill is greater than the speed of the ball before reaching the hill (Duit, 1981).

13%

10%

NGM059

Energy cannot be transferred from one object to another (AAAS Project 2061, n.d.).

12%

11%

Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.