Science Assessment

Students should know that:

1. Energy can be transferred by light when light from the light source shines on another object (receiver). For example, when a light bulb (or the sun) shines light on an object, energy is transferred from the light bulb (or the sun) to the object.
2. Light transfers energy through space; it does not need a medium such as air or another object in order to transfer energy from one object to another.
3. Light is given off by objects in all directions [except for lasers and other specially designed light sources or when the light is reflected or blocked] and travels in straight lines; therefore energy can be transferred from an object by light in all directions to any object in the path of the light.
4. Because light is transferred in all directions, the amount of energy transferred by light from a light source to an object decreases as the distance between the source and object increases.
5. The amount of energy transferred by light depends on the color of the light source. Light sources can give off light of different colors, ranging from red [through orange, yellow, green, blue] to violet.  For a given period of time and equal brightness, violet light can transfer the highest amount of energy and red can transfer the lowest amount of energy.
6. The amount of energy transferred by light depends on the brightness of the light source.  The brighter the light, the more energy can be transferred.  The dimmer the light, the less energy can be transferred.
7. The longer a light source shines on another object, the more energy is transferred from the source to the object.
8. When an object absorbs light, the object gets warmer, (unless energy is transferred away from the object), which means the thermal energy of the object typically increases.  For example, when the sun shines on a person, the person’s body becomes warmer.  When an object gives off light, the object gets cooler, which means the thermal energy of the object typically decreases (unless additional energy is supplied to the light source (e.g. a lamp plugged into an electrical outlet)). For example, as a glowing hot piece of metal cools, some of the temperature decrease is due to the fact that light is being given off. [This sub-idea assumes that neither object changes state, in which case the temperature of the object would not increase or decrease.]

Boundaries:

1. Students are not expected to know that all objects give off “electromagnetic radiation.”  This idea is limited to visible light.
2. Students are also not expected to know that the temperature of the object the light shines on increases asymptotically.  Items use time periods during which the temperature of the object noticeably increases the longer the light shines on the object.
3. Contexts of assessment items are limited to those that do not involve changes of state.

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.