BACKGROUND:
Humans can alter the atmosphere
by their activities on the surface of the Earth. There are six major
pollutants that are commonly recognized including: sulfur oxides,
particulate matter, carbon monoxide, nitrogen oxides, hydrocarbons, and
photochemical oxidants. The problems that they cause will be discussed
during the Post Lab. It is staggering to imagine that over 200,000,000
tons of pollutants are emitted into the air annually just by the people
of the United States.
This is just a simple way to focus
students attention that we put substances into the atmosphere. Much
of it is cleaned by rain or moved by wind. Scientists do not agree
on what all these pollutants are doing to our atmosphere. Some say
we are totally destroying our atmosphere real soon, others think nothing
will happen. The studies are very difficult to decipher, and it is
even harder for non-scientists to come up with an answer. The answer
probably lies somewhere between the two extremes. Remember your students
may one day vote on issues like this, that need a careful understanding
of the problem.
PROCEDURE:
- Air has several
components and this lab will illustrate that air can be chemically depleted
of some of its gases. Oxygen is needed for fire to burn and Experiment
1 shows students that the candle will burn as long as there is oxygen present,
but will go out when depleted of oxygen.
- Make sure you go over the
dangers of matches. You may want to divide the class so you watch
them performing the experiment at each table.
- The second experiment points
out that you can add components to air. When you burn a match, the
fire burns the match itself into particulate matter (soot).
- In the third experiment,
the burning of the leaves is causing carbon to be placed in the atmosphere.
Notice there will be water vapor that is released which is not harmful.
