there is a pond which is frozen , what is the temperature of the area just below the frozen part and deep inside the pond
Answers
Well, Another Amazing Consequence of Laws of Nature.
This answer is Generalized, So, people whose Concepts of Phases of Matter and Density, Temperature and Pressure are strong can directly start reading from ‘*** Answer Starts***’.
Those who want to revise the concepts, here I have discussed the concepts in brief to make the Answer clear.
Let us first clear the concepts of Phases of Matter and Density, Temperature and Pressure.
Quick Revision of Phases of Matter-
There are 5 Phases of Matter namely Gas, Liquid, Solid, Plasma and BEC (Bose-Einstein Condensate)
For this question, We would be mainly concerned about the first Three, that are Gas, Liquid and Solid. Among these three, Solids are the most closely packed and Gasses are most loosely packed, and Packaging in Liquid State lies in between that of Solids and Gasses, neither very closely nor too loosely.
Quick Revision of Density-
The degree of compactness of a substance. Mathematically, Density = (Mass/Volume).
For Example,
Let us take 2 Liquds in a container, both immiscible and of different Densities. Liquid with more Density would settle at the bottom and the less denser float above it. Just like Oil floats on Water.
If we compare multiple objects with each other, and take the same volume of each substance, then more the amount of matter present in that same amount of volume meaning more the Mass in that Volume more will be the Density.
Water melts at 0 °C (32 °F) but freezing is a more complicated affair. It is safe to say water gains the ability to freeze at 0 °C, but it can get much cooler before it actually does so resulting in supercooled water. Water in this state can rapidly solidify when suitable ice nuclei are introduced. For example, in convective clouds, liquid water can be observed at temperatures as low as -40 °C. However, the water in your pond isn't supercooled.
You say the air is 5 °F, but what is the temperature of the water (probably above 0 °C)? Ultimately it is the water that needs to be below freezing for ice formation to occur. How deep is the pond in your backyard? Water, compared to air, has a much better ability to retain heat and the bigger the volume of water, the more of a heat reservoir you have to deal with. Freezing itself is an exothermic process and ice formation will heat the surrounding water. The pond is probably not pure water and full of ions (e.g. salts) it has picked up from the ground, which lowers the melting point of water. All of these effects make it more difficult for water in your pond to actually freeze and could explain what you are seeing.
Of these effects, the heat capacity of the water and the temperature of the ground underlying the pond are probably the primary contributors. Underneath the pond is the ground and it too is a heat reservoir. Both are probably warmer than the melting point of water even though the air temperature is much colder. If a fluid is cooled from above, the cool fluid sinks toward the bottom. If a fluid is warmed from below, the warm fluid rises. Only one of these needs to be happening to start convection but it is likely that the ground below the pond is warmer than the pond and both the warm ground and cool air will drive convection in the pond. This, in turn, means your pond is well mixed and you will need to extract enough energy from the system to cool down all of the water and cool the ground below the pond to give ice the chance to form on the surface. This will take time (on the order of days/weeks) of continual sub-freezing air temperatures to accomplish. You'll have a much easier time freezing your pond than a large lake, but it still won't be an overnight process.