Angle of Contact and Temperature:
The angle of contact between a liquid and a solid surface is defined as the angle at which the liquid surface meets the solid surface. It is an important factor in determining the wetting behavior of a liquid on a solid surface.

Effect of Temperature on Angle of Contact:
- Decreases: With an increase in temperature, the angle of contact decreases. This is because the intermolecular forces between the liquid molecules decrease with increasing temperature, leading to a decrease in the surface tension of the liquid. As a result, the liquid tends to spread more easily on the solid surface, resulting in a smaller angle of contact.
- Reasoning: At higher temperatures, the kinetic energy of the liquid molecules increases, causing them to move more freely and overcome the cohesive forces holding them together. This leads to a reduction in the ability of the liquid to maintain a curved meniscus at the solid surface, resulting in a lower angle of contact.
- Consequence: A smaller angle of contact indicates better wetting of the solid surface by the liquid. This can have implications in various applications such as coating processes, adhesion, and capillary action.
- Experimental Evidence: Experimental studies have shown a consistent decrease in the angle of contact with an increase in temperature for various liquid-solid systems, confirming the relationship between temperature and the angle of contact.
In conclusion, the angle of contact between a liquid and a solid surface decreases with an increase in temperature due to the reduction in intermolecular forces and surface tension of the liquid. This understanding of the relationship between temperature and the angle of contact is important in various scientific and industrial contexts.