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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.
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.
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Temperature
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| Material |
Starting
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5 min
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10 min
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15 min
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20 min
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Change
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water |
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dry sand |
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wet sand |
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dry charcoal |
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wet charcoal |
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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."******
|
| __________ |
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
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." |
