Question

why can't you write properly with a chalk on a glass sheet

Answer 1

Here your answer
The surface of glass sheet is smooth, because of the smooth surface of glass the friction becomes less. This means the interlocking if molecules is also less because of the less interlocking of molecule we are unable to write on the glass sheet.
Hope this helps you friend
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Answer 2

we are not able to write properly with a chalk on a glass sheet because there is no friction taking place between both objects whereas glass is a smooth surface so friction can't be present at smooth surface . Friction needs rough surface to have action between them. Hence,we are not able to write properly with a chalk on a glass sheet.