Elenco Solar Energy - Manual (Page 5)

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Experiment no. 2 Converting sunlight into heat
This experiment seems so easy, elementary, even childish, that you probably won’t
want to try it! Go ahead, do it all the same. It is worthwhile!
Take 3 transparent cups of the same size that are either glass or plastic. Place one on
a dark sheet of paper and two on white paper. Stand these outside in sunlight and pour an
equal amount of cold water into each, about half a cupful should be enough. Measure
the temperature of the water in each with the thermometer.
Now, cover one of the cups that is on the white paper, with a transparent saucer, or even
some cling film.
Measure the temperature of the three cups
-after 10 minutes
-after 30 minutes
-after 60 minutes
Did you notice any differences? Did any of the results surprise you?
Some facts to help you with your observations and recordings:
a) A dark background generally absorbs more heat than a light background.
b) Glass or plastic absorbs a small quantity of the sun’s ray.
c) The glass of plastic retards the evaporation of water.
d) When water evaporates, some of the heat is lost since it is used up during the
evaporation process.
Experiment no. 3 Sunlight shinning through a window
Repeat Experiment No. 2, but this time, perform it on a table in a room with the
window closed. In other words, you will test sunlight which has passed through glass
windows.
Before you start, have a guess what the results might be. Even the scientist who
developed these experiments was not sure what the results would be until he tried it!
Experiment no. 4 The heat from an electric light bulb.
What would you expect to find if, instead of sunlight, you were to use the light of an
electric lamp on the ceiling of your room? Try it.
An electric light bulb gives out heat. It is absorbed in the room and y our thermometer
is not sensitive enough to register the difference.
Experiment no. 5 Black water
Supposing you were to dye the water you place in
the glasses black. Would you expect to obtain a
higher temperature? Could this idea be put to practical
use? Perhaps you could design an experiment to test
this idea (hypothesis).
If you have no black ink, you could make some by
dripping some water into the top of a dried felt tip
pen, collecting the water as it emerges from
the bottom. As an extra bonus, the dried out felt
tip pen will write again!
cartridge
ink