Temperature dependence of contact angle in liquids

[aim1732]

How does contact angle change with temperature and why? Does capillary rise have a temperature dependence?

 

[Andy Resnick]

Sure- look up the Marangoni effect.

 

[astrokreng]

The temperature dependence of contact angle in liquids is an important aspect of surface science and has been studied extensively. Contact angle is the angle formed between the solid surface and the liquid interface at the three-phase boundary. It is a measure of the wettability of a solid surface by a liquid.

As the temperature of a liquid increases, the contact angle decreases. This is because at higher temperatures, the molecules of the liquid have more thermal energy and are more mobile, allowing them to spread out and wet the solid surface more easily. On the other hand, at lower temperatures, the molecules have less energy and are less likely to overcome the adhesive forces between the liquid and the solid, resulting in a higher contact angle.

The change in contact angle with temperature can also be attributed to the change in surface tension of the liquid. As temperature increases, the surface tension decreases, making it easier for the liquid to spread out on the solid surface. This is why liquids with lower surface tension, such as water, have a more temperature-dependent contact angle compared to liquids with higher surface tension, such as oils.

Capillary rise, which is the phenomenon of a liquid rising in a narrow tube due to capillary action, also has a temperature dependence. As temperature increases, the surface tension of the liquid decreases, resulting in a decrease in capillary rise. This is because the adhesive forces between the liquid and the tube decrease, making it more difficult for the liquid to climb up the tube.

In conclusion, the temperature dependence of contact angle in liquids is a result of the interplay between thermal energy, surface tension, and adhesive forces. As temperature increases, the contact angle decreases due to the increased mobility and decreased surface tension of the liquid molecules. This also leads to a decrease in capillary rise, as the adhesive forces between the liquid and the tube decrease. This phenomenon has important implications in various fields, such as surface chemistry, material science, and microfluidics.