Thermal stability vs melting point

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Discussion Overview

The discussion centers around the concepts of thermal stability and melting point in ionic compounds, exploring the relationship between these properties and the implications for specific compounds like Na2O and MgO. Participants examine the differences between melting and decomposition, as well as the potential connections between thermal stability and melting points.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that an ionic compound's thermal stability increases with the reactivity of the metal cation, suggesting a correlation with decomposition difficulty.
  • There is a question about the relationship between thermal stability and melting point, with some participants arguing that no universal connection exists between the two properties.
  • One participant raises the distinction between melting as a physical change and decomposition as a chemical change, seeking clarification on this point.
  • Another participant confirms that there is no direct connection between melting point and decomposition point, emphasizing that decomposition results in a different substance.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the relationship between thermal stability and melting points, with multiple competing views on whether a connection exists. The distinction between melting and decomposition is acknowledged, but the implications for thermal stability remain unresolved.

Contextual Notes

Limitations include the lack of consensus on the relationship between thermal stability and melting point, as well as the dependence on specific types or families of compounds. The discussion does not resolve whether the properties can be universally applied across all ionic compounds.

sgstudent
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An ionic compound is more thermally stable when the metal cation is more reactive. So its harder to decompose. But then what's the difference between melting and decomposition?

Also, when an compound is harder to decompose, does it mean its melting point is higher? Because even though Na2O should be more thermally stable, it has a lower melting point than MgO.

Thanks so much for the help!
 
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sgstudent said:
But then what's the difference between melting and decomposition?

This one you should be able to answer by yourself. Cool the sample down - what will be the result in both cases?

As far as I know there is no direct connection between thermal stability and melting point. Or at least there is no universal connection - it may exist for specific types/families of compounds.
 
Oh ok. So when I say that Na2O is more thermal stable than MgO, I cannot use that to determine its melting point? Oh and is it that melting is a physics change while decomposition is a chemical change?

Thanks Borek!
 
sgstudent said:
Oh ok. So when I say that Na2O is more thermal stable than MgO, I cannot use that to determine its melting point? Oh and is it that melting is a physics change while decomposition is a chemical change?

Exactly. There is no connection between meting point and decomposition point. When a substance decomposes it is no longer the same substance it was before it decomposed. It is now a different substance.
 

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