Janice was researching combustion. During her research, she came across two different hypotheses—proposed at different times in
history—that both attempted to explain why certain objects burn. Hypotheses:
Burning is the chemical reaction of a substance with oxygen gas present in the air. The reaction produces water vapor and releases heat energy.
Certain objects are made from a combination of the elements water and fire. Applying heat to these objects separates the fire from the water.
To see which hypothesis better explained the process of combustion, Janice designed and performed an experiment.
Experiment:
A small candle was lit with a match.
The candle was allowed to burn for one minute.
The candle was covered by a glass beaker.
Observations:
The flame of the candle was very hot.
Shortly after being covered, the flame diminished and soon went out.
After the flame went out, water droplets formed on the inside of the beaker.
Which of Janice's observations is explained by Hypothesis I but not by Hypothesis II?
ANSWER: Janice's observation that is explained by Hypothesis I but not by Hypothesis II is that <u>shortly after the candle was covered by the glass beaker, the flame diminished and soon went out.</u>
REASONING:
Hypothesis I mentions oxygen as an important part of the chemical reaction that causes certain objects to burn. By placing the glass beaker over the candle, the oxygen supply is cut off. Once the oxygen inside the beaker is consumed, the flame diminishes and goes out.
Hypothesis II does not mention oxygen as an important part of the chemical reaction.
