What unique property of water allows organisms living in lakes to survive in below zero winter conditions ?
This anomalous expansion plays an important role by only freezing the upper layer in lakes and rivers.
During winter months in colder countries the outside or atmospheric temperature is very low - it drops to below freezing - and the upper layers of water in the lakes and ponds start cooling. When the temperature of the surface layers falls to 4 °C, the water body acquires maximum density and sinks down. The water that sinks down displaces water below, and the lower layers of water simultaneously rise up. This also gets cooled to 4 °C and again sinks down.
When the temperature of the water body finally goes below 4 °C, the density or heaviness of water decreases and as a result water does not sink down. The surface water finally freezes at 0 °C while the lower part still remains at 4 °C. The light frozen layer of ice floats on top.
The unique property of water that allows organisms living in lakes to survive in below zero winter conditions is its density.
Here are the steps explaining how water's density helps organisms survive:
Step 1: Water has maximum density at 4 degrees Celsius - As water cools down from higher temperatures, it becomes denser. However, as it cools below 4 degrees Celsius, it starts to expand and become less dense.
Step 2: Ice formation - When water reaches the freezing point, it forms ice. Unlike most liquids, ice is less dense than water, causing it to float.
Step 3: Insulation by ice layer - As the surface temperature drops below freezing, a layer of ice forms on top of the lake. This ice layer acts as an insulating barrier, preventing further heat loss to the atmosphere.
Step 4: Thermal stratification - As the surface water cools, it becomes denser and sinks, while warmer water from deeper layers rises. This creates thermal stratification, where the top layer of water is warmed by sunlight and remains relatively warm compared to the deeper layers.
Step 5: Maintenance of liquid water beneath ice - The relatively warm water in the lower layers remains liquid due to its higher density. This allows organisms to survive in the liquid water below the ice layer, even in below freezing conditions.
Step 6: Oxygen diffusion - Despite being covered by ice, lakes can still exchange gases with the atmosphere. Oxygen diffuses from the air into the liquid water, ensuring its availability for aquatic organisms.
The unique property of water that allows organisms living in lakes to survive in below-zero winter conditions is the fact that water has a high specific heat capacity.
To understand this, we need to explain what specific heat capacity is. Specific heat capacity is the amount of heat energy required to raise the temperature of a substance by a certain amount. In the case of water, it has a relatively high specific heat capacity, which means it can absorb and store a large amount of heat energy without significantly changing its temperature.
In the winter, when temperatures drop below zero, the surface of the lake freezes, forming a layer of ice. However, the water below the ice remains in a liquid state, creating a protective environment for the organisms living in the lake.
The high specific heat capacity of water plays a crucial role in this process. Before the temperature of the lake drops to freezing point, the water releases heat energy to the surrounding environment. As a result, it cools down gradually and prevents sudden temperature changes. This gradual cooling allows the organisms in the lake to adapt and avoid being exposed to extreme temperatures.
Additionally, the ice that forms on the surface of the lake acts as an insulating layer, preventing further heat loss from the water below. This insulation helps to maintain a relatively stable temperature for the organisms, minimizing the impact of freezing conditions.
In summary, the high specific heat capacity of water allows it to absorb and release heat energy, which helps organisms in lakes survive below-zero winter conditions by avoiding sudden temperature changes and creating an environment that remains relatively stable beneath the ice.