A child at the beach digs a hole in the sand and, using a
pail, fills it with water having a mass of 1.20 kg. The mo-
lar mass of water is 18.0 g/mol. (a) Find the number of
water molecules in this pail of water. (b) Suppose the
quantity of water on the Earth is 1.32 1021 kg and re-
mains constant. How many of the water molecules in
this pail of water were likely to have been in an equal
quantity of water that once filled a particular claw print
left by a dinosaur?
