Robert C. Chandler, Age 13, of Bridgeport Connecticut, for his question:

What is the difference between sleet and hail?

Rain, sleety hail and snow are formed in the turbulent atmosphere above our heads They condense frm fine water vapor as currents of damp air chase currents of dry air and layers of warm air sandwich between layers of cool air, eddying to and fro in constant upheaval. These conditions decide whether ';he condensed water vapor from the cloud shall reach the ground as snow, hails sleet or rain.

Hail always begins in the heart of a thunderstorm where cold, high air rides a warm, moist updraft from the ground, There vapor gels into tiny pellets of ice which start to fall earthward. On the way they meet the warm, rising wind and are tossed up again to cooler regions, This may happen many times before the hail finally bounces on the ground.

Each trip into the warmer region of the storm adds a mushy layer about the ice pellet. Each trip back to the cooler regions adds a new layer of hard ice. The hail stone gathers hard and soft ice in layers like an onion, Sometimes the updraft keeps them aloft until they have grown as big as marbles. Once, in Nebraska, a shower of five inch hail stones bounced onto the ground. Some of them weighed over a pound apiece.

If you catch a hail stone before it melts you can slice it open and find its onion skin layers of hard and softer ice. The layers can tell you much of its travels and history in the cloud from which it fell. Everyone is agreed that these hard little pellets of ice which fall from thunderclouds are hail stones.

However not everyone is agreed as to what should be called sleet. There was a tame when a mixture of rain and snow was called sleet. In fact, this is still so in many places. But this interpretation was not exact enough to satisfy our accurate weathermen.

When the weatherman speaks of sleet he means smallish particles of ice. These particles sat out from their cloud home as rain drops. As they fall they pass through a layer of cool air cool enough to freeze them into drops of clear ice,

Sometimes the world is glazed with a glistening coat of ice from    an ice shower. This is caused by rain drops, cooled below their freezing point, but unable to gel as ice until they strike a solid surface, It is only by chance that these rain drops did not freeze into    ice particles in the air and fall as sleet.

Is mercury a liquid or a solid?

Mercury or quicksilver, is a metal. Though when you see it run out from a broken thermometer, you would never compare it with the stiff metals such as iron, gold and copper. It runs and flows like water, gathering into shiny silver beads.

The fact is that mercury is in a liquid state at ordinary temperatures   other metals have to ire hosted to high temperatures before they will melt. Mercury begins to melt at the low temperature of 37.9 degrees Fahrenheit below zero. Colder than that, the fascinating metal is frozen solid as brass,

Somewhere around 675 degrees Fahrenheit mercury begins to boil and give off gases, But between its low melting point and its high boiling pointy it stays liquid.