Heating a substance causes molecules to speed up and spread slightly further apart, occupying a larger volume that results in a decrease in density. Cooling a substance causes molecules to slow down and get slightly closer together, occupying a smaller volume that results in an increase in density.
From: www.middleschoolchemistry.com
The method of separating mixtures by means of their differences in the chemical properties of the components is less convenient because these methods requires reactions therefore needs energy, increasing the costs for the process.
10 core electrons are in argon.
I think B
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