Science Assessment

Students should know that:

1. Convection is the transfer of energy by the movement of fluids (liquids or gases). The movement of the fluid can be due to temperature variations in the fluid or an external force like a fan.
2. Natural convection occurs from temperature variations within a fluid. Energy is transferred by natural convection in oceans, the air, and as molten rock moves in the earth’s mantle.
3. Forced convection occurs when the motion of the fluid is produced by an external source like a blower, fan, or suction device. Central heating and air conditioning systems rely on forced convection to transfer energy throughout buildings. Wind pushing surface water on oceans and lakes is another example of forced convection.
4. During convection, matter and its energy move from one location to another. This is unlike conduction, where energy is transferred without the transfer of matter.
5. The introduction of warmer fluid into a location increases the thermal energy of the fluid at that location and the introduction of cooler fluid into a location decreases the thermal energy of the fluid at that location.
6. Convection is usually the dominant form of energy transfer in liquids and gases (compared to conduction) because large quantities of liquids and gases can flow from one place to another within the fluid. Convection cannot occur in solids because regions of a solid cannot flow from one part of the solid to another.
7. Temperature variations can exist between different regions of a given sample of fluid. When a region of the fluid is warmer than the fluid around it, it rises, and when a region is cooler than the fluid around it, it sinks.
8. If a rising or sinking region of fluid encounters a boundary that blocks its movement (such as the top of a container or the surface of a liquid) the fluid will begin to flow horizontally along the boundary.
9. The combination of warmer regions of a fluid rising, cooler regions sinking, and movement along boundaries causes circulation of the materials that make up a fluid. 
10. Energy is transferred by way of currents when a fluid and the thermal energy that the fluid has circulates.

Boundaries:

1. Students are not expected to know how much warmer or colder a fluid needs to be than the fluid around it in order to circulate.
2. Students are not expected to know that the temperature of fluids affects their density and that this is why cooler regions of a fluid sink and warmer regions rise or that density differences cause the circulation of fluids as part of this idea. This idea is covered by the advanced convection idea.
3. Items not ask students to calculate how much energy is transferred by convection in a particular situation.
4. Assessment items at this level do not assess students’ knowledge of convection due to the rise and fall of the tides or variations in salinity or that convection is due to the differential effect of gravity on areas of different densities caused by differences in temperature.