Science Assessment

Students are expected to know that:

1. Thermal energy can be transferred by conduction when a warmer object (including liquids, like water, and gases, like air) is in contact with a cooler one. [Note: this is not the only way thermal energy can be transferred. See boundary statement 3.]
   1. Two objects must be in contact with each other for thermal energy to be transferred by conduction (which is not the case for radiation). This means that the sun does not transfer thermal energy directly to the earth.
   2. There must be a temperature difference between the objects in contact for thermal energy to be transferred by conduction. The greater the temperature difference the greater the amount of thermal energy that can be transferred by conduction (assuming the mass or type of material is held constant).
   3. The thermal energy transferred by conduction goes from the warmer object to the cooler one.
   4. As thermal energy is transferred by conduction the thermal energy (and temperature) of the cooler object will increase and the thermal energy (and temperature) of the warmer object will decrease until the objects are at the same temperature. [This sub-idea assumes that neither object changes state, in which case the temperature of the object would not increase or decrease as the change of state was occurring. Assessment items are limited to contexts in which there is no change of state.]
2. Energy can be transferred mechanically when one object pushes or pulls on another object over a distance.
   1. In order for energy to be transferred mechanically there must be a change in position and/or shape (the push or pull must act over a distance).  This energy transfer will stop if the motion/changing of position stops. 
   2. Energy will be transferred mechanically the entire time the push or pull is acting (in the direction of motion) and energy transfer will stop when the push or pull stops.
   3. When two pushes or pulls act over the same distance, the stronger push or pull transfers more energy mechanically than the weaker push or pull.
3. Energy can be transferred electrically when an electrical source, such as a battery or generator, is connected in a complete circuit to an electrical device, such as a light bulb, speaker, heater, or motor.
4. Energy can be transferred by electromagnetic radiation.
   1. Electromagnetic radiation is always given off by all objects and energy is transferred when this electromagnetic radiation is absorbed by another object.
   2. Electromagnetic radiation can transfer energy through space; therefore, objects do not need to be in contact with each other in order to transfer energy by radiation.
   3. The amount of electromagnetic radiation given off by an object can depend on the temperature of the object. The higher the temperature of an object, the more electromagnetic radiation the object gives off.
   4. When energy is transferred to an object by radiation, the temperature and thermal energy of the object typically increase.  When energy is transferred from an object by radiation, the temperature and thermal energy of the object typically decrease. [This sub-idea assumes that neither object changes state, in which case the temperature of the object would not increase or decrease. Assessment items are limited to contexts in which there is no change of state.]
   5. This is the mechanism by which the sun transfers energy to the earth.
5. Students should know that as energy is transferred from one system to another, energy transformations can also occur.

Boundaries:

1. Examples of mechanical energy transfer that students should be familiar with include the energy transfer that occurs 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. Assessment items should use contexts in which it is clear that the object supplying the energy has less energy after the transfer and the object receiving the energy has more energy after the transfer. For example, when a ball is thrown, it may be hard to appreciate that your body is loosing energy. Note that this may also be true for other forms of transfer. For example, it may not be obvious that an object that radiates energy loses energy.
2. Students are not expected to know that conduction occurs through collisions of atoms.
3. Students are not expected to know that convection and diffusion are other ways by which thermal energy is transferred.
4. Although students are expected to know that when energy is transferred, a decrease of energy somewhere is accompanied by an increase in energy somewhere else and vice versa, they are not expected to know that the total amount of energy in the system is conserved.
5. Students are not expected to keep track of how much energy is transferred by each mechanism.