Barry Madore, age 8, of Ottawa, Ontario; for his  question:

Why isn't the rain ever salty?

The clouds, we are told, are moisture evaporated from the earth below. And most of the earth is covered with salt sea water. So most of the clouds must have been evaporated by the smiling sun from the face of the sea. All this is true. Then why isn't most of the rain salty? Instead, when it falls through clean air, rain is the purest water in nature,

Lets hear some facts about evaporation„ Evaporated milk is thicker than ordinary milk, Only the water has been driven off, the rest is all there with less water. A sugar mill uses an evaporator to dry out crystals from liquid syrup, When water evaporates from the sea, it leaves the dissolved materials behind it. Maybe a little salt blows off in the air, but not enough to flavor the raindrops,

When it evaporates, water turns from a liquid into a gas. It needs a lot of heat for this job, On a stove, it gets a lot of heat at once. It boils off into steam and vapor in a short time, The sun smiles with less heat over a longer time, But it takes the same amount of heat to evaporate one pint of water the fast way or the slow way.

Water evaporates into tiny particles too small to imagine. Write the figure six and follow it with 21 zeros. That is roughly the number of water particles in a small raindrops Each one is made of two atoms of hydrogen and one atom of oxygen tightly welded together, The chemist’s shorthand for water is H20   2 hydrogen and one oxygen atoms.

In liquid form, the particles tend to cling together, They have a strong attraction for each other called cohesion. They are also moving. They dash about and collide with each other, the warmer the water, the faster its particles are rushing about. For heat is no more than the movement of these little particles,

With more heat, they rush about still faster. Soon some of them go fast enough to break the cohesion that clings them together. These particles become air borne as water vapor,

Vapor is gas and gas needs more room than liquids or solids, Seam needs 16,000 times more space than liquid water. The sunshine on the sea is far gentler than a steam kettle. Its beams warm the water near the surface. They do not reach boiling point and turn into steam.

They get up quite a lot of speed, but not enough to break the cohesion that holds them to other particles. Soon the particles below the surface are warmed and start to gather speed. They jog and jostle the surface particles, one good Jolt from below is enough to launch a surface particle into the air. Once free of its brothers it is air borne vapor on its way to join a high flying cloud.

But the tiny particle cannot take along any baggage as it leaps up:  It can only launch itself. The salt and other stuff in the sea is left behind, Day by day, the salt sea becomes saltier as more pure water is evaporated from its surface