Question

Explain why when water is kept in the freezer water starts freezing from the top?

Answer 1

When a glass of water is frozen , the formation of ice starts from the top , *and* the melting of ice also starts from the top , bottom and the sides . The reason is this .

When water is cooled , maximum density is reached at 4 degree centigrade . Due to this ice that is formed as the temperature goes down , floats on the water . This gives an impression that ice formation has started at the top .

Then slowly you will see ice formation on the sides and at the bottom . Ice itself is a bad conductor of heat . So as the crust is formed from the floating ice , further cooling from top is reduced . The cooling proceeds through the sides of glass and the bottom and the water close to the sides and the bottom gets frozen next . This leaves a center that has water , or sometimes a hollow center .

When the process of unfreezing begins , the surface that is exposed to atmosphere lets heat come in . Thus the top , the sides and bottom of the glass allow heat to come in . This forms water on the sides and at the bottom . The ice begins to melt from all sides . If enough ice melts , the rest of the ice floats on the water formation at the bottom . This gives the impression that melting started from the bottom . It actually starts from all the surface of the ice and works its way inside .

MARK BRAINLIEST...

Answer 2

Because it has less density then liquid water at 0 degree and empty spaces are created. Therefore, ice freeze from top to bottom. Because the water-air boundary has a higher heat exchange rate. Thus a thin ice layer forms there first.