Question

in cold areas the upper surface of lakes becomes ice because of ice at 0C?
a) heavier than water
b)water and ice weight as that of water
c)lighter than water
d)none of these​

Answer 1

Answer:

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c) lighter than water

Answer 2

Warm water generally gets more dense as it gets colder, and therefore sinks. This fact may lead you to believe that ice should form on the bottom of a lake first. But a funny thing happens to water as it gets even colder. Colder than 4° Celsius (39° Fahrenheit), water begins expanding and becomes less dense as it gets colder. As a result, close to freezing, colder water floats to the top and the warmer water sinks to the bottom. The density of water as a function of temperature can be seen in the plot on the right. Eventually, the coldest water, which has floated to the top of the lake in wintry conditions, freezes to form a layer of ice. Right when the water freezes to ice, the ice becomes significantly less dense than the water and continues to float on the lake's surface.Ice is less dense than water because of the way it forms a hexagonal crystalline structure. Each water molecule consists of two hydrogen atoms bonded to the bottom of an oxygen atom. When ice forms, the hydrogen atoms of one water molecule form weak hydrogen bonds with the top of the oxygen atoms of two other water molecules. Lining up the water molecules in this pattern takes up more space than having them jumbled randomly together (as is the case in liquid water). And because the same mass of molecules takes up more space when frozen, ice is less dense than liquid water. For this same reason, water below 4° Celsius becomes increasingly less dense as it gets colder. Close to freezing temperatures, the molecules in the liquid water begin to line up into the space-filling hexagonal structure.