Science Assessment

Students should know that:

1. The atoms and molecules that make up an object are constantly in motion, and when they collide they transfer energy from one to another. 
2. When rapidly moving atoms or molecules collide with slower moving atoms, there is a net energy transfer from the rapidly moving atoms to the slower moving atoms. The slower moving atoms increase in speed while the rapidly moving atoms decrease in speed.
3. Energy is transferred from a warmer part of an object to a cooler part of the object or from a warmer object to a cooler object when the objects are in contact, through the random collisions of atoms or molecules.
4. When the faster moving atoms and molecules of a warmer object (or part of an object) collide with the slower moving atoms and molecules of a cooler object (or part of an object), the average speed of the faster moving atoms and molecules decreases, which means that the warmer object (or part of an object) gets cooler and, therefore, has less thermal energy than before.  The average speed of the slower moving atoms and molecules of the cooler object increases, which means that the cooler object (or part of an object) gets warmer and, therefore, has more thermal energy than before.
5. Different substances will transfer energy by conduction at different rates depending on the types of atoms/molecules that make them up.
6. The transfer of energy by conduction typically occurs faster in solids and liquids than in gases because the atoms or molecules that make up a solid or liquid are more closely packed compared to the atoms or molecules that make up gases, and therefore the atoms and molecules that make up a solid or liquid are in closer proximity to other molecules with which they can interact.

Boundaries:

1. Items do not ask students to calculate how much energy is transferred by conduction in a particular situation.
2. Contexts of assessment items are limited to those that do not involve changes of state.
3. While the mass of the atoms or molecules of a substance and interatomic bonding play a role in determining how much kinetic energy the atoms or molecules have and, therefore, how much energy can be transferred by conduction, items use contexts in which the atoms or molecules of the warmer object are moving faster than the atoms or molecules of the cooler object so that mass or bonding do not have to be considered.

Students should know that:

1. In a fluid system in which the fluid is the same temperature throughout, the upward forces and downward gravitational force are balanced and natural convection will not occur.
2. When a region of a fluid is heated, it becomes less dense. When a region of a fluid is cooled, it become denser. The gravitational force on a denser region is greater than the gravitational force on a less dense region of equal volume.
3. Heating a fluid from below will create a warmer region that is less dense than the cooler, denser region above it. When a warmer region of a fluid is below a cooler region, the upward force and downward gravitational force are unbalanced so that the warmer region rises and the cooler region sinks.
4. As the warmer region rises, its thermal energy is transferred from one location in the fluid to another.
5. As a region of fluid moves to new locations, adjacent regions of fluids move in to fill the space left behind.
6. When the rising fluid encounters a boundary such as the surface of the fluid, it moves horizontally. As regions warmer than the surroundings move horizontally, they transfer energy to the surroundings, and this causes the fluid to cool and become denser. This region then begins to sink when it becomes denser than the region below it. As the region sinks, its gets closer to a heat source causing its temperature to increase and its density to decrease, and the cycle continues.

Boundaries:

1. Items do not ask students to calculate how much energy is transferred by convection in a particular situation.
2. Students are not expected to know how much denser a fluid needs to be than the fluid around it in order to fall.
3. Assessment items do not use the term “buoyant force,” nor will they assess students’ understanding of buoyant forces.