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Badly worded question? (chemical vs physical changes)

  • Thread starter sp3sp2sp
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  • #1
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Homework Statement


The question states: "Which of following changes that affect the composition of our atmosphere involve physical changes and which involve chemical reactions?"
Then the question lists 6 different scenarios and I have to sort them into either "chemical reaction" or "physical change".
Two of the the scenarios are:
"human activities such as the combustion of fossil fuels has increased the levels of greenhouse gases."
"human activities such as the combustion of fossil fuels generate aerosols."


Homework Equations




The Attempt at a Solution


I realize that combustion is always a chemical change, but when they list two effects of it, thats what confusing me. Is the question asking whether the combustion of fossil fuels is chemical or physical, or is it asking whether increased greenhouse gases and the generation of aerosols are chemical or physical? thanks
 

Answers and Replies

  • #2
tnich
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Homework Statement


The question states: "Which of following changes that affect the composition of our atmosphere involve physical changes and which involve chemical reactions?"
Then the question lists 6 different scenarios and I have to sort them into either "chemical reaction" or "physical change".
Two of the the scenarios are:
"human activities such as the combustion of fossil fuels has increased the levels of greenhouse gases."
"human activities such as the combustion of fossil fuels generate aerosols."


Homework Equations




The Attempt at a Solution


I realize that combustion is always a chemical change, but when they list two effects of it, thats what confusing me. Is the question asking whether the combustion of fossil fuels is chemical or physical, or is it asking whether increased greenhouse gases and the generation of aerosols are chemical or physical? thanks
Do you have some scenarios for which both answers would be true? If so, could you list them them in both categories and designate the part of the scenario that applies to each category?
 
  • #3
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Increase in greenhouse gases is a physical change but those gases come from the burning of fossil fuels. Thats why I think the question is ambiguous isnt it? I dont have option to choose both categories
 
  • #4
tnich
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Increase in greenhouse gases is a physical change but those gases come from the burning of fossil fuels. Thats why I think the question is ambiguous isnt it? I dont have option to choose both categories
Maybe you could look at the processes involved. Can you write chemical formulae for production of greenhouse gases? How about for aerosols?
 
  • #5
Borek
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I agree, question is ambiguous. It would be a quite nice open question, checking your understanding of the processes involved, but if you are expected to classify it just confuses.
 
  • #6
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But just to make sure I am correct that it actually is badly worded, isn't it because:

Burning of fossil fuels is a chemical change (combustion).
Increase in greenhouse gases is a physical change (simply an increase in V of gases)

Is this correct?
 
  • #7
Borek
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Yes, more or less. I would prefer to speak about change of amount and concentration of greenhouses than about change in their volume (even if technically that's correct).
 
  • #8
CWatters
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It is a badly worded question but I would just answer chemical for the first and physical for the second.

We aren't adding C02 to the atmosphere. We are mostly taking oxygen out, chemically altering it by reacting it with carbon and putting it back.

Edit: Actually we are releasing CO2 by causing chalk/calcium carbonate to be dissolved at an increasing rate.
 
  • #9
Borek
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We aren't adding C02 to the atmosphere. We are mostly taking oxygen out, chemically altering it by reacting it with carbon and putting it back.

Edit: Actually we are releasing CO2 by causing chalk/calcium carbonate to be dissolved at an increasing rate.
Can you elaborate? I have a hard time trying to understand what you mean.

By my book we are removing the O2 and replacing it with an equimolar amount of CO2. As in effect the amount of CO2 in atmosphere grows I see no problem with using the word "adding".
 
  • #10
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Incorrect! I answered that
"human activities such as the combustion of fossil fuels has increased the levels of greenhouse gases." = chemical change.
"human activities such as the combustion of fossil fuels generate aerosols." = physical change
=wrong. (doesnt specify whether one or both are wrong)

edit: sorry it actually gave feedback..says that "1 out of the 5 items were sorted incorrectly"
 
  • #11
CWatters
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