At normal temperatures, liquids generally expand when heated and contract when cooled. This is their natural expansion property. But water is the liquid we use the most of all the existing liquids.
Water contracts when heated from 0°C to 4°C. When water is
cooled from room temperature until it reaches 4°C its density decreases. When
it is cooled below 4°C, its bulk increases and its density decreases.
Specifically, we can see the density of water at 4°C. This
property of water is known as the paradoxical expansion of water. The exact
reason for this is unknown as it is a natural phenomenon.
Generally in cold countries, the surface temperature of lakes
is lower than their base temperature during winter.
Because the density of ice is less than that of normal
water. Water that freezes below 4 degrees Celsius floats above normal water and
comes to the surface of lakes due to the anomalous expansion of water.
The surface of lakes and ponds is covered by a thin layer of
ice, but the water below remains unfrozen and protects aquatic life. This is why nature has given water a paradoxical expansion.
During the daytime, the sun's radiation warms the land faster
than the seawater because the land has a lower thermal capacity.
That is, the material with the least specific heat capacity heats
up first. When we heat an aluminium vessel and a brass vessel together the
aluminium heats up first. This is because the thermal conductivity of aluminium
is less than the thermal conductivity of brass. This means aluminium's specific
heat capacity is lesser than brass.
That is why the specific heat capacity of land is lower than
the specific heat capacity of seawater even if the sunlight is the same.
Therefore, during the day the land gets warmer than the seawater and as a result, the air over the land expands and becomes less dense and
rises. At that time, the cold air on the surface of the sea blows towards the
land and we call it sea breeze.
In contrast, the land
surface cools faster than the sea surface at night due to the low specific heat
capacity of the land. The material with the lowest specific heat capacity will
cool first, so the land surface will cool first then the sea surface. As a
result, the air over the ocean expands and its density decreases and it rises.
At that time, the dense cold air over the land blows towards the sea and we
call it the land breeze.
That is why when we go to the beach during the day time than
at night time we can feel the cool breeze.