Does the Same Copper Cup Equalize Heat Loss Rates for Different Liquids?

[nithin]

Ok hi guys,
recently i was doing a practical on thermodynamics. Then i came across of a question which was to comment on the assumption that the rate of heat loss for 2 different liquids , placed in identical calorimetry copper cups was the same.( the 2 liquids started off at the same temperature ( the liquids were oil and water)).

Ok my reasoning for the rate of heat loss being the same was that the copper cup,can only have a loss in energy at a fixed amount of power as the dimensions of the cup are kept constant. Please correct me if i am wrong.

Then i also commented on Newtons law of cooling( rate of change of temperature is proportional to the difference in temperature between the objects temperature and the ambient temperature) If it were to be written in a equation,it would be the (rate of change in temperature = -k(T - Troom) . Okay the k here is a constant which is different for every object.My reasoning is that to bring down the temperature of 2 different objects by a kelvin would require different amounts of energy as the the specific heat capacity of every object is unique. Furthermore the rate of energy loss is the same,hence 2 different objects would not have the same k value.As they would require different amounts of time to cool down. Please comment on these statements

 

[denverdoc]

well buyer beware as its free advice and i have never taken thermodynamics course.
IME its usually most fruitful to compare the most polar opposites possible, even where it may make little practical sense.

So into cup 1 I place water, well characterized, and the basis for the calorie unit.

Into cup 2, I pour the same volume from a neutron star, magically cooled to the same temperature but just as dense. Or a cup of magma.

Will the rate of heat loss vary? In the first instant, i should think not. In the second, maybe. By the twentieth instant, most assuredly. There is still a significant gradient with the container of enormous heat capacity, whereas with water there may not be. Thats why the Earth's core remains molten while we scrub our backs with pumice stone. So in essence I agree, very different rates of cooling and heat flux thru the container as a fx of time.

 

[m2003]

Hello,

Thank you for sharing your thoughts on thermodynamics cooling. I can provide some clarification and additional information on your comments.

Firstly, your reasoning for the rate of heat loss being the same for the two liquids in identical calorimetry copper cups is correct. This is due to the fact that the copper cups act as a constant heat sink, meaning they will absorb and dissipate heat at a fixed rate. Therefore, the rate of heat loss for the two liquids will be the same as long as the cups are identical and the initial temperatures of the liquids are the same.

Your understanding of Newton's law of cooling is also correct. The constant k represents the specific heat transfer coefficient, which takes into account the unique properties of each object such as its specific heat capacity and thermal conductivity. Therefore, two different objects will have different k values and will cool at different rates, even if they are placed in identical conditions.

It is important to note that the rate of energy loss is not the same for two different objects. The rate of energy loss, or heat flow, is dependent on the temperature difference between the object and its surroundings. However, the rate of temperature change, or cooling rate, is dependent on the specific heat transfer coefficient and the temperature difference between the object and its surroundings.

I hope this helps to clarify any confusion and provides a deeper understanding of thermodynamics cooling. Keep up the good work in your practicals!