How does the entropy of the system change?

Question

I know entropy is the tendency toward randomness or disorder in a system, but can someone please explain how the entropy of a system changes by these factors:

water vapour condensing

sugar dissolving in water

complete oxidation of methane

decomposition of calcium carbonate

Thank you so much!

Answer 1

1.  water vapour condensing = phase change to a liquid, a more ordered state of matter, entropy  (Sº)  decreases

2.  sugar dissolving in water = crystals dissolve to form an aqeous solution, more disorder, Sº increased

3.  complete oxidation of methane =  first, look at the balanced equation:

CH4  +  2O2  ==>  CO2  +  2H2O

Equal moles - no change there,

Look at O2, an element (purest form of matter) combines with another element - more disorder, increased Sº

Look at heat, Hº, it increases, therefore, so does Sº

Overall, an increase in Sº

4.  decomposition of calcium carbonate =

2CaCO3  ==>  2Ca  +  2CO2  +  O2

More moles as a product, therefore increased Sº