CoachAn ocean is one of the very large stretches of salt water that cover most of the Earth and lie between the continents. A sea is a smaller stretch of salt water, usually at the edge of an ocean and partly closed in by land.
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Example 3.3 (How salty is the sea?)
In a bottle holding one kilogram of sea water — about one litre — there are about 35 grams of salt. If we let all the water evaporate, the salt stays behind as white crystals at the bottom. That is how sea salt is made in salt marshes by the sea, where the sun and the wind slowly dry out shallow pools of sea water.
Example 3.7 (A drop on the mountain)
A drop of rain falls as snow on a high mountain in winter. It stays there, frozen, until the warm days of summer. Then it melts, runs down into a mountain stream, joins a river, and the river carries it to the sea. One sunny day the drop evaporates from the sea and rises into the air, where it becomes part of a new cloud.