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HEAT TRANSFER IN THE ATMOSPHERE,
CONDUCTION, CONVECTION, RADIATION
OR WHY DOES HOT AIR GO UP?
STUDENT EXPECTATIONS
Upon completion of this unit, students will be expected to know or have a better understanding of:
- How heat is transferred by conduction, convection, and radiation.
- Why hot dry air is pushed upward by cool or moist air.
- How thermals can help produce instability in the atmosphere.
- How the convective process in the atmosphere builds clouds and strong convection builds hail.
- How to construct a hot air balloon from tissue wrapping paper.
- How to safely launch their hot air balloons.
STATE STANDARDS
The following Colorado Model Content Standards for Science will be met or exceeded: (Unless otherwise noted, the standards for grades 5 through 8 are used.)
Standards: 1, 2, 2.1, 2.2, 2.3, 4.2, 4.3, 5, 6
The following TEXAS Essential Knowledge and Skills for Science will be met or exceeded: (Unless otherwise noted, the TEKS for Middle School Science are used.)
TEKS 6.1A,B, 6.2A,B,C,D,E, 6.3A,C,, 6.4A, 6.6A,C, 6.8B, 6.9A,B, 6.12B, 6.14C, 7.1A,B, 7.1A,B, 7.2A,B,C,D,E, 7.3A,C,, 7.4A,B, 7.6A,B, 7.14A,B, 8.1A,B, 8.2A,B,C,D,E, 8.3A,C, 8.4A,B, 8.5A,B,C, 8.7A, 8.10A,B,C
Other standards from other specific subject areas and grade levels may also be covered.
TEACHER NOTES
Conduction is heat transfer from molecule to molecule. If someone touches an ice cube or hot plate they know because the heat is transferred from the warmer object to the cooler object from molecule to molecule. Remember heat always travels from high concentration to low concentration. If something feels cold, it is because the heat is going from you to it.
Convection is heat transfer by a circulation of rising warm air(less dense) and sinking cooler air (denser). In reality, the more dense air sinks forcing the less dense air upward. We have all heard that warm air rises because it is less dense, but we sometimes forget that moist air is less dense than dry air. This, simply put, is because the atomic mass of a water molecule is 18amu and the mass of dry air is around 29amu, so warm moist air forms convection currents better than warm dry air. This is also why the more convective a cell or cloud becomes, the greater the chance it will produce hail and severe weather. Convection is extremely important in the summer time along the eastern Rockies and Plains states just east of the Rockies, as convection currents will build thunderstorms that rise to above 50,000 ft in elevation. (Emphasize that the more dense air forces the lighter air to rise. Don't just say "hot air goes up.")
Radiation is heat transferred by infrared waves. We have all felt the warmth of the sun or heat from a camp fire without touching them. We also know that light colored clothing reflects the heat and dark absorbs the heat. This is all due to infrared radiation or radiant heat. We also know that on a summer day, the infrared gets in our car and heats it up, but is absorbed inside the car and when you open the door, wow! It is hot!
ACTIVITY DESCRIPTION
In this activity, students should be divided into groups of at least 3 but no more than 4 depending on class size. Constructing balloons is fun, launching them is more fun, but they should not loose focus on the ideas that they are demonstrating: heat transfer in the atmosphere. They should also remember that the faster and farther the air rises in the atmosphere, the greater chance of hail and severe weather.
MATERIALS
(FOR STUDENTS)
- 9 pieces of wrapping tissue paper (Don't use the metallic foil type. It is too heavy.)
- 1 glue stick (This is light weight and does not melt like tape, nor make the mess of liquid glue.)
- 1 piece of aluminum wire about 18 inches long (Picture hanging wire works well.)
- Heat Transfer worksheet (HTML version)
- or Heat Transfer worksheet (PDF version)
(FOR TEACHERS)
- Coleman (or similar type) camp stove. The pump-up kind seems to produce more heat than the propane ones, but propane ones are fine.
- 3ft water heater vent pipe with flanged end.
- Heat resistant gloves. (Welding gloves work fine)
METHODS/PROCEDURES
- Follow the steps in the PowerPoint presentation to construct a tissue paper balloon.
- Launch the balloon by slipping the wire opening of the balloon over the vent pipe on the camp stove. The balloon fills with the rising air by convection from the atmosphere, heated and dried by the camp stove and up the pipe. Be careful not to overlap the balloon over the end of the pipe. Tissue paper burns very easily…Have a fire extinguisher handy! If the balloon does catch fire, if possible, pull it to the ground and put it out. Don't let it go up!
RESULTS/CONCLUSIONS
Have the students answer the questions on their worksheets explaining how the three methods of heat transfer were used and how rising air can cause a severe thunderstorm to develop and how strong rising air currents or updrafts can cause hail.
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