Why is the concept of amount of substance as a quantity confusing?

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Discussion Overview

The discussion revolves around the concept of 'amount of substance' as quantified by the mole, exploring its necessity and relationship to mass. Participants question the rationale behind having a separate unit for counting substances when mass is already a measure of quantity.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the need for a unit like the mole when mass is already available as a measure.
  • Another participant challenges the idea that mass can adequately represent the 'amount of substance' by providing examples of different materials with the same mass but potentially different amounts of substance.
  • A participant suggests that the mole is necessary if there exists a minimum indivisible mass of a substance.
  • It is proposed that a counting number as a unit is essential for converting from a discrete scale of molecules to a continuous scale of mass, facilitating the transition from number to amount.
  • One participant reiterates the strangeness of having a unit like the mole, questioning the discomfort with the concept without providing a clear explanation.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between mass and the amount of substance, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

The discussion highlights the need for clear definitions of 'amount of substance' and the assumptions underlying the use of the mole as a unit, which remain unspecified.

adityatandon
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I never really understand why we should have a 'unit' for a 'count' i.e. the mole. And what is the need of assigning a separate quantity, the amount of substance... we already have 'mass'; don't we ?

P.S. - I mistyped the topic title... It should be "Amount Of Substance as a quantity"
 
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And how do you think mass is a measure of the 'amount of substance'? If you have one kilogram worth of feathers, and one kilogram worth of steel, do you feel the 'amount of substance' is the same?
 
The "mole" is only needed if there is some indivisible minimum mass of a substance...
 
You need to define a counting number as a unit so that you can convert from a discrete scale "number of molecules" to what appears to be a continuous number "number of kilograms". It completes the step from number, to amount.
 
Nick89 said:
And how do you think mass is a measure of the 'amount of substance'? If you have one kilogram worth of feathers, and one kilogram worth of steel, do you feel the 'amount of substance' is the same?

Err... that depends on how we define 'amount of substance'

flatmaster said:
You need to define a counting number as a unit so that you can convert from a discrete scale "number of molecules" to what appears to be a continuous number "number of kilograms". It completes the step from number, to amount.

So we have a number (one mole) as a unit ? Appears strange...
 
adityatandon said:
So we have a number (one mole) as a unit ? Appears strange...
Why does it appear strange? You aren't explaining why you are uncomfortable with the concept.

You do understand what atoms and molecules are, right?
 

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