Question

when change in entropy is positive?

Answer 1

when you condense gas to liquid and liquid to solid entropy will be -ve and for vice versa the entropy will be +Ve

Answer 2

can we say 'change in entropy is positive when heat enters'?

Answer 3

note certainly Bcoz heat may not increase the entropy right :)
it again depends how much of heat ?
but yes i think we can say for large heat supply

Answer 4

gawd how do i write equation i ve a question