Fully understanding the effects of specific heat

Question

I have yet to find a source that adequately explains our reasoning behind why we describe something as "hot" and something as "cold".

Textbooks describe the water as something that is less hot than the sand in the summer, and conversely less cold than the sand in the winter. I know that H20 has stronger hydrogen bonds that make it harder for the sun to the H20 particles breaks apart. This decreases the avg KE of the water.

However, is my perception of hotness not due to the Temp (avg KE) of a substance, but rather the actual change in internal heat? Change in internal energy ΔU = Q - W. I assume that the sun ray's give the water just as much energy as the sand, and I assume that there is no difference between the work of the water and the sand. Thus, is the change in internal temp not the same?

If hotness is due to a difference in Temp, then why would the sand be colder than the water in the winter? The strong hydrogen bonds make it hard for the water molecules to increase in KE regardless of whether or not it is winter or summer, so wouldn't the sand then always be "hotter" than the water?

Answer 1

In fact your perception of hotness is not due to temperature but rather due to heat transfer rate from the medium to your body's sensory receptors. When someone says that "water is less hot than sand in the summer" they are not using any objective concept of hotness. That sentence actually means that in the summer there are more heat flowing from sand to your skin than from water to your skin. That is due to the fact that sand has larger thermal conductivity than water. An objective definition of hotness would be given by the temperature of the body and since sand and water (in thermal equilibrium) are at the same temperature, we cannot say one is hotter than the other.