How come rain is fresh water although the oceans are salty? Shouldn’t the rain be salty?
Jerry T., Chicago
Salt in sea water is merely dissolved in the water as a solution, not chemically bonded to it. Thus, when water evaporates only pure water returns to the atmosphere. Salt and other impurities are left behind. Residents of ocean coastal areas know that air blowing in from the ocean contains salt because their rusting automobiles attest to it, and it is for the same reason that the oceans are salty. When airborne droplets of salty ocean spray evaporate, their minute specks of salt are left floating in the air. So, the answer to your question is simple: Only pure water evaporates, leaving impurities like salt and other substances in the ocean.