Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 11

# Why Do Marine Animals Live Deep Inside a Lake When the Surface of the Lake Freezes? - Physics

Why do marine animals live deep inside a lake when the surface of the lake freezes?

#### Solution

Water possesses an anomalous behavour. The volume of a given amount of water decreases as it is cooled from room temperature, until its temperature reaches 4 °C. Below 4 °C, the volume increases, and therefore the density decreases.

When the temperature of the surface of lake falls in winter, the water at the surface becomes denser and sinks. As, the temperature reaches below 4 oC , the density of the water at surface becomes less. Thus, it remains at surface and freezes. As, the ice is a bad conductor of heat, it traps the heat present in the lake's water beneath itself. Hence, no further cooling of water takes place once the top layer of the lake is completely covered by ice. Thus the life of the marine animals inside the lake is possible.

Concept: Temperature and Heat
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#### APPEARS IN

HC Verma Class 11, Class 12 Concepts of Physics Vol. 2
Chapter 1 Heat and Temperature
Short Answers | Q 6 | Page 11