The purpose of the uninoculated control tubes used in this test is that two uninoculated control tubes are needed to show the results of the medium in both aerobic and anaerobic environments. It is used to show it is sterile and also as a color comparison, used also to show that the medium remains green under both conditions.
Because of pollution from factories and other activities that release harmful gases into the air
"The water becomes warmer."
<u>Remember</u>: Kinetic energy means how much, on average, a molecule is moving around. This is directly translated into heat. Therefore, the higher the kinetic energy, the more heat produced.
Your answer would be "Chemical Change"
The correct answer really is B.
If you are directed to break that rule then you better be in a high level chemistry class. When I taught things like that I insisted that students just wait until the chemical permeated the fume cabinet and even then I was always very nervous.
Sometimes you have to know when to ignore a bad direction. If you are working with chlorine, for example, you should be especially careful. That stuff was used in WWI as part of a chemical warfare technique. Many men suffered grotesque deaths by breathing it in, particularly if they were in trenches. Chlorine is heavier than air. It sinks to the lowest level.
