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Lessons & Units

A database of lessons and units searchable by content and cultural standards, cultural region and grade level. More units will be available soon. You can use Acrobat Reader to look at the PDF version of the Cover Sheet for the Units and Self-Assessment for Cultural Standards in Practice.

Winds
And
Weather

by Jonas Ramoth and Sidney Stephens

Activity Series 2 - Heat Absorption and Radiation*

"When you see what looks like fog rising from the lakes and ponds, their heat temperature is balancing with the air's." **

Background

Some parts of the earth's surface absorb and store heat from the sun more readily than others. The uneven absorption causes uneven radiation of heat to the air near the surface and creates convection currents. This uneven absorption and emission of heat at the earth's surface depends upon three primary factors: (1) a substance's ability to absorb or reflect radiant energy; (2) a substances ability to store internal energy and; (3) the amount of radiant energy striking the substance. This lesson deals with items 1 and 2. See Heating the Earth for treatment of item 3.

Absorption and reflection are opposite processes. A good absorber of radiant energy takes in much more energy than it reflects, including the range of radiant energy we call light. A good absorber appears dark and it becomes warm readily. Good absorbers are also good emitters, giving off their heat readily to the surface around them. Good reflectors, on the other hand, are poor absorbers and appear light. Clean snow is a good reflector and therefore not a good absorber. Clean does not melt rapidly in sunlight. If the snow is dirty, it absorbs radiant energy from the sun and melts faster." ***

Different substances also have different capacities for storing internal energy and require different quantities of heat to raise the temperature of a given mass of the material by a specified number of degrees. "Water has a much higher capacity for storing energy than all but a few uncommon materials. A relatively small amount of water absorbs a great deal of heat for a correspondingly small temperature rise. Water also takes a long time to cool, a fact that explains why hot-water bottles used to be employed on cold winter nights. This tendency on the part of water to resist changes in temperature improves the climate in many places significantly changing its temperature.

Activity 2a

Materials
Per pair or team: data table, 5 Styrofoam cups, 5 thermometers, scissors, ruler, 1 flood lamp (150 watt bulb), water at room temperature, dry sand, finely crushed dry charcoal

Procedure

"When you see what looks like fog rising from the lakes and ponds, their heat temperature is balancing with the air's."****

Gear-Up 1. Ask students what this quote means and if they have similar or different observations to share. Probe for understanding
Explore 2. In pairs or teams, cut the Styrofoam cups in half about 3 cm from the bottom.

3. Fill one cup with water at room temperature, one with dry charcoal, one with wet charcoal, one with dry sand, and one with wet sand.lamp

4. Arrange the cups evenly in a circle directly under the desk lamp but do not turn lamp on yet.

5. Place a plastic-backed thermometer flat across the surface of each cup. You can support the thermometer on the tops of the Styrofoam cups.

6. After the thermometers have been in place for 5 minutes (with the lamp off), record the temperature of each material in the starting temperature column on the data sheet.

 

 

Temperature

Material
Starting
5 min
10 min
15 min
20 min
Change

water

           

dry sand

           

wet sand

           

dry charcoal

           

wet charcoal

           

 

 

7. Record temperature readings at 5-minute intervals for the next 10 minutes (temperature can also be read at shorter intervals if desired).

8. Turn off the lamp and record temperatures at 5-minute intervals for another 10 minutes.

9. Calculate heat gain and heat loss for each material.

10. Using different colored pens for each material, create a line graph of data.

Generalize

11. Of the dry materials, which showed the greatest temperature change, light or dark? Of the wet solids?

12. Did the dry solid show more temperature increase than the same solid when wet?

13. Did the temperature of the water increase as much as the temperature of the solids?

14. When the light was turned off, which of the substances cooled the most in 5 minutes? The least?

Activity 2b

Explore/
Generalize
15. This activity suggests that the amount of heat radiated into the air depends upon the kind of material that is beneath the air. Design, conduct and analyze an experiment, either indoors or out, to further test this hypothesis. (Note: since so little of the sun's energy reaches Alaska during the winter, this activity, if done outdoors, is best done in spring or fall. See Activity Series 4 Heating the Earth.)
Apply/Assess

16. Uneven absorption and emission of heat sets up convection currents that produce winds. Classic examples of this are land and sea breezes, illustrated below. "In the daytime, the shore warms more easily than the water. Air over the shore rises and cooler air from above the water takes its place. The result is a sea breeze. At night the process reverses as the shore cools off more quickly than the water - the warmer air is now over the sea."******

cycle

__________

17. If the average sea surface temperature of Kotzebue Sound is 12 C° during July, and the average high and low land air temperatures are 20C° and 4C° , (assume daytime and nighttime temperatures), would the same land breeze/sea breeze phenomena apply? Does this match your experience and those of the TF?

18. Do you suppose this land/sea breeze phenomenon holds true for Selawik Lake in July? If so, why? Diagram the convection currents/wind direction you'd expect during the day and at night.

19. Does this prediction match your observations and those of the TF?

20. How might you expect Selawik Lake to influence local winds during the dead of winter?

(For performance assessments also, see http://www.ctl.sri.com/pals for Grades 5-8: "Heat Retention" and "Sun and Temperatures")


 

* Adapted from Intermediate Science Curriculum Study (1972) p.7-10

** Martz, C. (1999) p. 5

*** Hewitt, P.G. (1998) p. 276

**** Adapted from Intermediate Science Curriculum Study (1972)

***** Martz, C. (1999) p. 5

****** Hewitt, P. 1997, p 328


 

Standards

Section I - Observing Locally

Section II - Understanding Wind

Section III - Connecting Globally

Appendix A - Selawik Weather Information from Jonas Ramoth

Appendix B - Assessment

Appendix C - Weather Resource List

Appendix D - Interdisciplinary Integration


 

 

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Math Story Problems
St. Lawrence Island Rain Parka Winds and Weather Willow
Driftwood Snowshoes Moose
Plants of the Tundra Animal Classification for Yup'ik Region Rabbit Snaring
The Right Tool for the Job
Fishing Tools and Technology
Blackfish Family Tree
Medicinal Plants of the Kodiak Alutiiq Archipelago Beaver in Interior Alaska Digging and Preparing Spruce Roots
Moose in Interior Alaska Birds Around the Village  

 

Handbook for Culturally Responsive Science Curriculum by Sidney Stephens
Excerpt: "The information and insights contained in this document will be of interest to anyone involved in bringing local knowledge to bear in school curriculum. Drawing upon the efforts of many people over a period of several years, Sidney Stephens has managed to distill and synthesize the critical ingredients for making the teaching of science relevant and meaningful in culturally adaptable ways."

 

 

Go to University of AlaskaThe University of Alaska Fairbanks is an affirmative action/equal opportunity employer and educational institution and is a part of the University of Alaska system.

 


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Last modified August 18, 2006