when the ice on a lake goes out in the spring a large portion of it will sink instead of melting why?

Answer 1

It doesn't sink. It just gets covered with water. It melts from the top to the bottom. Eventually the weight of the water may crack the ice and cause it to buckle

Answer 2

The increased weight of the impurities in the water, will tend to make the ice appear to be lower in the water than normal.

Answer 3

Ice will not sink. it's less dense than water. water is its most dense at 4 Celsius, not frozen at that point.