Science Assessment ~ Ideas ~ Motion energy (kinetic energy) is associated with the speed and the mass of an object.

Key Idea: The amount of elastic potential energy stored in a stretched or compressed elastic object increases when the object is further stretched or compressed because stretching and compressing an object changes the distances between the atoms and molecules that make up the object.

Sub-Ideas
Items & Student Performance
Misconceptions
NGSS

Students should know that:

There are both attractive and repulsive forces between the atoms and molecules that make up an object. These forces result in a stable separation of the atoms and molecules.
Compressing or stretching an object changes the distances between the atoms and molecules that make up the object. When an elastic object is stretched or compressed, interatomic (monatomic substances) and intermolecular forces tend to restore the atoms and molecules to their unstretched or uncompressed positions. The energy an elastic object gains as atoms or molecules are moved closer together or farther apart from their unstretched or uncompressed position is elastic potential energy.
The amount of elastic potential energy an object has increases as the distance between the atoms and molecules increases from the unstretched or uncompressed distance (when the object is stretched) and increases as the distance between the atoms and molecules decreases from the unstretched or uncompressed distance (when the object is compressed).
The amount of elastic potential energy an object has depends on the strength of the interatomic and intermolecular forces that tend to restore the atoms and molecules to their original positions. The stronger the interatomic and intermolecular forces, the greater the amount of elastic potential energy for a given change in atomic or molecular positions.

Boundaries:

Students are not expected to calculate the change in elastic potential energy that is stored in any particular elastic object when it is stretched or compressed. The sub-ideas above describe semi-quantitative relationships. Students are expected to compare relative distances and interatomic forces to determine relative amounts of elastic potential energy.
Students are not expected to know the strength of the interatomic and intermolecular forces for any particular pair of atoms or molecules. In assessment items, the comparative strength of the forces will be provided when necessary.
In assessment items, objects are not stretched, compressed, twisted, or bent beyond the point where they would return to their original shape (i.e. no plastic deformation).

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 4–5	Grades 6–8	Grades 9–12
RG197001	The stronger the intermolecular forces, the greater the amount of elastic potential energy there is for a given length stretched.	N/A	46%	49%
RG167002	Stretching a rubber band increases the amount of elastic potential energy because the distance between the molecules that make up the rubber band increases, and intermolecular forces act to restore the molecules to the unstretched distance.	N/A	46%	47%
RG130002	Stretching a spring increases the elastic potential energy because the distance between the molecules that make up the spring increases, and forces between the molecules act to restore the molecules to their original separation.	N/A	36%	36%

Frequency of selecting a misconception
Misconception ID Number	Student Misconception	Grades 4–5	Grades 6–8	Grades 9–12
EGM063	Objects that are easier to stretch have more elastic energy than objects that are harder to stretch (AAAS Project 2061, n.d.).	N/A	23%	23%
RGM104	Elastic potential energy is not related to the inter-molecular forces between the molecules that make up an elastic object.	N/A	20%	20%
EGM034	Elastic potential energy is the potential for an object to be stretched or compressed. For example, a rubber band has less elastic energy when it is stretched very far than when it is stretched a little bit because it can’t be stretched much more and a rubber band that is stretched a little bit has more elastic energy because it can be stretched a lot more (AAAS Project 2061, n.d.).	N/A	14%	14%

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.

NGSS Statements
Code	Statement
PS1.A HS	The structure and interactions of matter at the bulk scale are determined by electrical forces within and between atoms.
PS3.C HS	When two objects interacting through a field change relative position, the energy stored in the field is changed.
PS3.A MS	A system of objects may also contain stored (potential) energy, depending on their relative positions.
PS3.A HS	These relationships are better understood at the microscopic scale, at which all of the different manifestations of energy can be modeled as a combination of energy associated with the motion of particles and energy associated with the configuration (relative position of the particles). In some cases the relative position energy can be thought of as stored in fields (which mediate interactions between particles). This last concept includes radiation, a phenomenon in which energy stored in fields moves across space.