Science Assessment

Students should know that:

1. When two objects collide, their speeds change compared to their speeds before the collision and energy is transferred from the object that slows down to the object that speeds up. [Note: An exception to this is when two identical objects collide at a 45-degree angle. Assessment items will not assess students’ understanding of the exceptions.]
2. Energy is transferred by forces as long as one object exerts a force on another object. The transfer of energy stops when one object no longer exerts a force on the other object.
3. When two forces act over the same distance and in the same direction, the stronger force transfers more energy than the weaker force.

Boundaries:

1. This idea is limited to transfers of energy as a result of direct contact forces and elastic collisions and is limited to systems containing two objects that are moving or that can be moved. Examples of direct contact include when billiard balls hit each other, when a ball is thrown or kicked, when a baseball or golf ball is hit with a bat or club, when an object is set in motion by a rubber band or spring, or when a bobsled or swing is pushed.
2. Assessment items include contexts where there is a clear transfer of energy (one object will slow down and the other will speed up). Items do not include collisions between objects that are significantly different in mass where the change in speed of the more massive object is negligible.
3. For direct contact interactions, assessment items may include situations where both objects are moving or one object is moving and the other object is at rest.

Students should know that:

1. A vibrating object (such as a guitar string, a drum, or a tuning fork) can transfer energy to another object by producing sound that travels through a material such as air, water, or another solid object between the two objects.
2. A medium (solid, liquid, or gas) is required in order to transfer energy by sound.  Sound cannot travel through empty space (a vacuum).
3. In a given medium, the amount of energy that is transferred by sound is related to the loudness and pitch (how high or low the sound is) of the sound.  The louder the sound, the greater the amount of energy transferred; the higher the pitch, the less the amount of energy transferred.
4. The amount of energy that can be transferred by sound decreases the farther away the source of the sound is from the receiver.
5. The amount of energy that can be transferred by sound increases the greater the size of the receiver.
6. When energy is transferred to a receiver by sound, the receiver gains energy and, as a result, its motion or temperature may change.  This gain in energy may be difficult to detect.
7. A vibrating object that transfers energy by sound needs a continuous input of energy to keep it vibrating. Otherwise, the vibrations slow down until the vibration stops and no more energy is transferred.

Boundaries:

1. Assessment items are limited to one vibrating object producing a sound wave.
2. Contexts used in items are limited to audible sound.
3. At this level, students are not assessed on the idea that when sound passes through a medium, the temporary displacement of matter in the medium is a sound wave.
4. At this level, students are not assessed on the relationship between the properties of sound waves and sound. For example, they are not expected to know that loudness depends on the amplitude of the sound wave or that pitch depends on both amplitude and frequency. These ideas are covered by the advanced idea.