Using 3 – 4 sentences explain (in your own words) why water expands when it freezes?

In the case of water, that is, when the liquid water gets cooled, it gets contract to a temperature of about 4 degrees is attained. However, after that, it starts to expand somewhat till it moves towards the freezing point, and eventually when it freezes, it expands by about 9 percent.  

This characteristic has its source in the composition of the water molecule. In water, there possesses a capacity to produce a network of hydrogen bonds, where each atom of hydrogen is in a line amongst the two atoms of oxygen. This tendency of hydrogen bonding gets robust as the temperature lowers down. The formed ice structure is completely hydrogen-bonded and these bonds permit the structure to get open, thus, expansion takes place.  

a saline water is fed to a reverse osmosis unit at flow rate o rotameter connected to reject (retentate) line reads 8 installed in reject and permeate line reads 15.2 milli siemens/cm and 300 micro siemens/com respectively.

they are all solids.