Heat water; mechanical (the movement of a turbine is based off of mechanical energy, not chemical or potential).
72g H2O x 1 mol H2O/18.02g H2O = 3.99 mol H2O
I’m not sure if there was important information in the question before this one, but the answer based on the info I have is B.
The density of water is 1kg/L. Since the density of the block is less, it will float.
You must first calculate the total weight of 1 mole of the substance. You do this by finding the molar weights on the periodic table of each of the elements in the compound:

So now we take the amount of each element that is given in the compound and divide it by the total mass of the compound:
Carbon: 96.08g

Carbon = 49.48%
Nitrogen: 56.028g

Nitrogen = 28.85%
Oxygen: 31.998g

Oxygen = 16.48%
First and foremost, they are completely different substances with each exhibiting unique properties. Both have different atoms involved on their structures which is the cause of the differing properties.