Key Idea: Temperature variations in fluids such as air and water lead to currents that circulate the fluid, and this circulation transfers thermal energy from place to place in the fluid.

Students are expected to know that:

  1. When a region of a fluid (e.g., air or water) is warmer than the fluid around it, it rises, and when a region is cooler than the fluid around it, it sinks.
  2. If the rising or sinking fluid encounters a boundary that blocks its movement (such as the top or bottom of a container, or the surface of a liquid) the fluid will begin to flow horizontally along the boundary.
  3. 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.
  4. The continuous circulation of the material that makes up the fluid creates a current. The current moves fluid from place to place, and in doing so it transfers thermal energy from place to place within the fluid. The movement of a fluid with a lot of thermal energy increases the temperature of the fluid at the place where it moves and the movement of a fluid with little thermal energy decreases the temperature of the fluid at the place where it moves.

Note: This idea addresses the process of convection in general, so examples used for items testing this idea will not necessarily be specific to the earth system.

Boundaries:

  1. Students are not expected to know how much warmer or colder than the fluid around it a fluid needs to be in order to circulate.
  2. Students are not expected to know that as the fluid moves, energy is also transferred out of the circulating system by conduction and radiation.
  3. Students are not expected to know how density differences cause the circulation of fluids as part of this idea.
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number
Knowledge Being Assessed Grades
6–8
Grades
9–12
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CL138001

As a jar of water is warmed from the bottom, the water at the bottom of the jar becomes warmer than the water around it and starts to rise.

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CL021002

The rising and falling of warm and cold air causes the circulation of air that causes wind to blow along the surface of the earth.

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CL015002

Warm air that is blown across a cool room causes the thermal energy on the other side of the room to increase.

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CL002002

As a jar of water is warmed from the bottom, the water at the bottom of the jar becomes warmer than the water above it and starts to rise, and its thermal energy rises with it.

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CL137001

When a container of water is warmed over a flame, warmer water at the bottom rises toward the top and the colder water at the top sinks toward the bottom.

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CL006002

Air currents form when warm air rises and cold air sinks.

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CL010002

When warm air blows into a classroom and the air is the same temperature as the air inside the room, the air coming in will neither rise nor sink because it is the same temperature as the air around it.

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CL003002

Air moves from place to place, and its thermal energy moves with it.

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CL011002

When a container of water is warmed from the bottom, the warmer water at the bottom of the container rises to the top and colder water at the top sinks toward the bottom of the container.

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CL007002

Ocean currents form when warm water rises and cold water sinks.

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CL008002

When cold air comes into contact with warmer air around it, the cold air will sink.

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CL016002

Warm air around an electric heater will rise toward the ceiling, move toward the walls, and then sink back to the floor.

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CL014002

Convection currents can occur in gases and liquids but not in solids.

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CL001002

When warm air comes in contact with colder air around it, the warm air rises and its thermal energy rises with it.

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Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8
Grades
9–12

CLM043

Convection currents cannot occur in gases (AAAS Project 2061, n.d.).

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CLM042

Convection currents cannot occur in liquids (AAAS Project 2061, n.d.).

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CLM041

Convection currents occur in solids (AAAS Project 2061, n.d.).

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CLM040

Cold air has "coldness" that can cool the air around it (AAAS Project 2061, n.d.).

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CLM039

Cold air sinks only if it is a lot colder than the air around it (AAAS Project 2061, n.d.).

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CLM038

Ocean currents form only because wind pushes the water, not from the rising and falling of warm and cold water (AAAS Project 2061, n.d.).

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CLM037

When air moves, its thermal energy moves separately from the moving air (AAAS Project 2061, n.d.).

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CLM036

Warm air always rises regardless of the temperature of the air around it (AAAS Project 2061, n.d.).

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CLM035

Air currents form only because of the rotation of the earth, not because of the rising and sinking of warm and cold air (AAAS Project 2061, n.d.).

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CLM034

When water is moving, its thermal energy moves separately from the water (AAAS Project 2061, n.d.).

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CLM031

Only very warm air carries thermal energy (AAAS Project 2061, n.d.).

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CLM030

Moving air does not carry thermal energy (AAAS Project 2061, n.d.).

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CLM029

When a container of water is heated from the bottom, the water will not rise until it starts to boil (AAAS Project 2061, n.d.).

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Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.