Question

explain which type of change occurs when water is electrolysed.

Answer 1

when water is electrolyzed, a chemical reaction occurs. water is made up of two atoms of hydrogen and one atom of oxygen. when electrolysed water breaks up into its constituent elements i.e, hydrogen and oxygen  

Answer 2

a chemical change occurs when water is broken down into oxygen and hydrogen. electrolysis of water and hydrogen gas and oxygen gas therefore it's a chemical change and since from water to gas conversion therefore physical change as well and of it is irreversible since hydrogen gas and oxygen when in contact don't produce water.

hope it helps