Convection Box (Tove)
Author
Tove Aitchison, Robert Frost Middle School
Principles
Convection Currents - as the candle heats the air above it, the cool smoky air is drawn through the box.
Standards
NGSS
MS-ESS2-6.
Develop and use a model to describe how unequal heating and rotation of the Earth cause patterns of atmospheric and oceanic circulation that determine regional climates. [Clarification Statement: Emphasis is on how patterns vary by latitude, altitude, and geographic land distribution. Emphasis of atmospheric circulation is on the sunlight-driven latitudinal banding, the Coriolis effect, and resulting prevailing winds; emphasis of ocean circulation is on the transfer of heat by the global ocean convection cycle, which is constrained by the Coriolis effect and the outlines of continents. Examples of models can be diagrams, maps and globes, or digital representations.] [Assessment Boundary: Assessment does not include the dynamics of the Coriolis effect.]
California 6th Grade Science Standards 2009
Energy in the Earth System
4.Many phenomena on Earth’s surface are affected by the transfer of energy through
radiation and convection currents. As a basis for understanding this concept:
a.Students know the sun is the major source of energy for phenomena on Earth’s
surface; it powers winds, ocean currents, and the water cycle.
b.Students know solar energy reaches Earth through radiation, mostly in the form of
visible light.
c.Students know heat from Earth’s interior reaches the surface primarily through
convection.
d.Students know convection currents distribute heat in the atmosphere and oceans.
e.Students know differences in pressure, heat, air movement, and humidity result in
changes of weather.
Materials needed
convection box
tea candle
lighter
paper
Procedure
Open the window of the convection box, and light the tea candle. (It should have been placed under one of the chimneys.)
Then quickly close the window.
Light paper and hold it over one of the chimneys (the one that is not over the candle.) The smoke will go down into the box, and will exit the box over the candle.
Then make a rotor out of aluminium foil and hold it over the chimney with the candle.
Explanation
Convection occurs when a fluid is heated, and then expands. As the fluid expands the mass doesn't change so the fluid becomes less dense The fluid then rises through the denser fluid around it.
Specifically the convection box shows that when air is heated, it becomes less dense and rises through the layers of colder and thus denser air.
How does the principle of convection apply to land and sea breezes? (The land heats up during the day. This heat is transferred to the air above it which heats up, expands, and rises. The void is filled by cooler air from the sea.)
How does a hot air balloon work? (The air inside the balloon is heated, expands and moves upward. This air movement causes the balloon to rise when the heated air gets trapped inside the balloon.)
How does water boil in a pot? (The water is heated by conduction from the burner to the water in the bottom of the pot. The water gets hot, expands and rises to the top of the pot. Colder denser water moves to the bottom of the pot to fill the void. It then gets heated, expands, and rises, causing a circular motion.)
Everyday examples of the principles illustrated
Land and Sea Breezes
A radiator
A steaming cup of hot coffee
Photos
Below is a picture of the convection box.
Questions
Movies
Movie of the convection box while the candle was lit.
Movie of the convection box immediately after the candle was blown out.