how many molecules of water are there in 10g of ice?
In 1 mole of anything there are 6.022 × 10²³ molecules (Avogadro's constant), so in 10 g of water there are (0.556 mol)(6.022 × 10²³ molecules/mol) = 3.35 × 10²³ molecules. (Note that it does not matter whether you have ice, liquid water, or steam.