Density decreases that's why ice floats on water because it's less dense than water.
The compound sodium carbonate is a strong electrolyte because it completely dissociates when placed in water into its component ions. The equation of the reaction can be expressed as:

The dissociation leads to the formation of sodium and carbonate ions with the latter held together by its internal covalent bond.
This is unlike weak electrolytes that do not dissociate completely in water or aqueous solutions. Only a small fraction of the solute exists as ions in the solution.
More on strong and weak electrolytes can be found here: brainly.com/question/3410548
HEY THERE
THATS EASY...
YOU CAN USE A MAGNET TO ATTRACT THE IRON FILLINGS WHICH WOULD THEN SEPARATE FROM THE SAND.
Answer:
Hydrogen and Oxygen
Explanation:
also it can be written as H2O