[PFScience]

I've been doing some thermodynamics revision and in several of the equations, temperature (T) is factored in:

ΔS_surr = -H/T

ΔG = ΔH - TΔS

S = q/T

In these the temperature is referenced as constant, and this is fine if all you are doing is conducting it at RTP, but obviously you may need to conduct experiments at different temperatures. What are the different ways that this is achieved and which is most efficient?

For example...I've seen hot plates used but how reliable are they in keeping temperature constant? Is there a way of using bunsen burners to an acceptable accuracy?

[Corribus]

I think you'll have some trouble with a Bunsen burner. Of course, it depends on what kind of experiment you are doing and what temperature range you are interested in. For spectroscopy, a good quality Peltier heating element equipped with a good quality thermocouple and a feedback mechanism can reliably control temperature to fractions of a degree.  The highest quality DSCs and other thermal analytical equipment, which is what you should be using for very accurate determination of thermodynamic values anyway, can regulate and measure/temperature with amazing precision. I mean, they have to, for the very reason you ask your question.

[PFScience]

Much appreciated.... what are your thoughts on water baths? Due to the high heat capacity, I presume its a reasonably accurate device for isothermal exp ? What are the special pans/vessels called that you do the reaction in?

[Corribus]

The think the tool needs to fit the experiment. Water baths can be good, but they are usually big, which can mean temperature gradients. There may be very little temperature fluctuation at the point where the temperature is measured, but maybe a big (constant) differential between different areas of the bath. The only way to truly know is to measure the temperature at various points as a function of time. In the end, it may not matter if your application doesn't require amazing precision. Water baths are used routinely, for example, in sous-vide cooking. For a sensitive thermal measurement, it may not be adequate. DSC samples are small for a reason.