Effect of temperature on capillary rise

[Binayak95]

We all think that by increasing the temp of a liquid, the surface tension would reduce and so capillary rise will not be as high. But on increasing the temp, the liquid's density also decreases and so the weight of liquid to be lifted also reduces. Which will have the dominating effect, decrease in the weight of liquid leading to an increase in capillary height or a decrease in the surface tension causing a fall in the capillary height?

 

[haruspex]

It will depend on the liquid and the temperatures involved. E.g. water gets denser from 0C to 4C.

 

[Andy Resnick]

Presumably you are referring to equilibrium, as opposed to say, thermocapillary flow (Marangoni effect). AFAIK, the interfacial energy is a monotonically decreasing function of temperature (since it goes to zero at the liquid-gas phase transition), but the temperature dependence of the contact angle is less clear- at least, I couldn't easily find any useful data.

Since we are discussing equilibrium, the usual formula applies and the variation of height will go as δ(σ/ρ), where σ is the interfacial energy and ρ the density (assuming the contact angle remains constant).