The aerosol can is sealed, and under pressure. Place it on a heat source, and the gas inside expands. Upon expansion with no outlet, the vessel may explode.
Pressure cookers work on this principle, as food can be cooked at higher temperatures than
100
∘
C
. Pressure cookers have safety valves, that will operate if the internal pressure becomes too high.
Limestone rocks dissolving in water. All other options are forms of physical weathering.
Answer: C) Not all scientific knowledge begins with an experiment
Explanation:
Fleming's lab was very messy, and one day when he is back from his vacations, he noticed that a colony of a fungus had grown as a contaminant on one of the Petri dishes sown with a bacteria called <em>Staphylococcus aureus</em>. Fleming observed a bacterial lysis, which means the death of the bacteria.
<u>The dishes got contaminated by Penicillium</u>, which is a mold that produces a an antibacterial substance, called penicillin. <u>This is an antibiotic that attacks a wide range of bacteria.</u>
At first, his findings were underestimated and he was not able to isolate this penicillin. But in 1940, Howard Florey and Ernst Chain found out that <u>this antibiotic could be used as a therapeutic agent to fight bacteria.</u>
So, in this case the discovery of penicillin was accidental, without planning a specific experiment.
