why is it that when ice freezes, only the first layer freeze?

Question

please help me with the question.thanks!!

Answer 1

because the cold air only reaches/blows on the top not the bottom...get it?

Answer 2

Like others have said, it freezes first at the surface because that's where the heat is leaving and that's the portion of the water that first reaches freezing temperature. But, there's more to the story.

When water molecules settle down from moving around in liquid state to just vibrating in place in solid state, something interesting happens. The attractive forces, which cause a molecule to "stick" when it joins the solid, do work on the molecule as it is drawn in. The effect of this work is extra heat in the system, which warms up the nearby water a bit and delays additional freezing.

This prevents water from freezing on the inside, in most cases. Any molecules that try to stick together in the middle to start an ice cube will heat up the water around them enough to remelt them. It's only at the boundaries that the extra heat has someplace to go that is not water.

Such heat that appears or disappears during a state change is commonly called "latent heat", but also has the more imposing name: "enthalpy". In this case, the terms to Google--uh, Yahoo!-- are "latent heat of fusion" or "enthalpy of fusion".

Answer 3

Almost every solid will sink in its own liquid form, except water. Water is at greatest density a few degrees above 0 Celsius, and so ice at 0 degrees C is slightly LESS dense than the surrounding water, so it floats. Good thing, too, because otherwise our planet would have solid ice everywhere except for a thin layer of melt water in summer.

Answer 4

the top level of ice freezes, but as ice is less dense than water, it stays on the surface. the water below keeps circulating, keeping it from completely freezing.

Answer 5

I think because that layer is the layer that is most exposed to the cold air but i wouldn't know for sure I always say look it up!