Question

Why does a layer of ice form on the surface of a pond during freezing weather?

Answer 1

Water freezes from the top down—which allows ice to float—because of a strange quirk in how water's density behaves at falling temperatures. ... At 4 °C water is still in its liquid form. In lakes and rivers, this water will cool at the surface, grow denser, and descend.

Step-by-step explanation:

Answer 2

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. ... Ice is less dense than water because of the way it forms a hexagonal crystalline structure.

Step-by-step explanation:

Hope that helps!