Does temperature affect mass in chemistry

AI Thread Summary
Cooling a substance before measurement is important from a chemistry perspective, particularly when dealing with hygroscopic materials. Hot samples can cause convection currents in the surrounding air, leading to inaccuracies in mass measurements due to the ascending force created by the warm air. Additionally, cooling helps prevent the sample from reabsorbing moisture from the air, which is critical for hygroscopic salts. Analytical balances are typically calibrated at room temperature, making it essential to allow samples to cool to ensure accurate readings.
TheShapeOfTime
I asked this question in the physics general forum and didn't get a solid answer. They say temperature won't really matter here, so what would be a reason to let the substance cool, from a chemistry point of view?
 
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TheShapeOfTime said:
I asked this question in the physics general forum and didn't get a solid answer. They say temperature won't really matter here, so what would be a reason to let the substance cool, from a chemistry point of view?

Hi,
Don´t get surprised about it.

It´s just a problem of convection flux in air. If the sample is hot, the air surrounding it is warmed and it starts going upwards. Due to the non-zero viscosity of the air this can lead into an ascending force in the sample, altering the measure.
 
Temperature does not affect mass but it does effect the instrument measuring mass. Analytical balances are calibrated at room temperature.
 
Perhaps in your case the reason is to avoid the sample reabsorbing water (hot things that are getting cooled tend to absorb water). And you´re working with an higroscopic salt, so the cooling must be done in dry atmosphere before measuring.
 
Thanks for your replies!
 
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