Effect of Temperature on Surface Tension
Surface tension is inversely proportional to the temperature.
i.e. 𝛾 ∝ 1/T
We know that kinetic energy of molecules increases with increasing the temperature. Due to this increased kinetic energy, water molecules move quickly and weakening the cohesive forces that hold them together. Consequently, the surface tension of water decreases with increasing the temperature.
On the other hand, decreasing the temperature, slows down molecular movement of molecules, make the cohesive forces stronger and increases the surface tension.
At the critical temperature of a liquid, the surface tension becomes zero because at this point, the liquid and its vapor phase become indistinguishable, and the cohesive forces at the surface are completely overcome by the thermal motion of the molecules.
The relation between temperature and surface tension can be described by the following empirical equations-
𝛾 = 𝛾o − 𝑘 𝑇
where, 𝛾 is the surface tension at temperature 𝑇
𝛾o is the surface tension at a reference temperature (at or near the freezing point of the liquid)
𝑘 is a proportionality constant specific to the liquid.
Test Your Knowledge
Effect of Temperature on Surface Tension MCQs
1. How is surface tension related to temperature?
A. Surface tension is directly proportional to temperature.
B. Surface tension is inversely proportional to temperature.
C. Surface tension is independent of temperature.
D. Surface tension increases with increasing temperature up to a certain point, then decreases.
View Answer
Option B is correct answer.
Surface tension is inversely proportional to the temperature.
2. Why does the surface tension of water decrease with increasing temperature?
A. Increased kinetic energy strengthens cohesive forces.
B. Decreased molecular movement allows for stronger hydrogen bonds.
C. Increased kinetic energy causes molecules to move faster, weakening cohesive forces.
D. The liquid and vapor phases become distinguishable at higher temperatures.
View Answer
Option C is correct answer.
We know that kinetic energy of molecules increases with increasing the temperature. Due to this increased kinetic energy, water molecules move quickly and weakening the cohesive forces that hold them together. Consequently, the surface tension of water decreases with increasing the temperature.
3. What happens to the surface tension of a liquid at its critical temperature?
A. It reaches its maximum value.
B. It becomes infinite.
C. It becomes zero.
D. It starts to fluctuate rapidly.
View Answer
Option C is correct answer.
At the critical temperature of a liquid, the surface tension becomes zero because at this point, the liquid and its vapor phase become indistinguishable, and the cohesive forces at the surface are completely overcome by the thermal motion of the molecules.
4. In the empirical equation 𝛾 = 𝛾o − 𝑘 𝑇, what does 'k' represent?
A. The surface tension at the critical temperature.
B. The temperature at which surface tension is zero.
C. A proportionality constant specific to the liquid.
D. The cohesive force between molecules.
View Answer
Option C is correct answer.
A proportionality constant specific to the liquid.
5. If the temperature of a liquid is decreased, what is the expected effect on its surface tension?
A. Surface tension will decrease due to increased molecular movement.
B. Surface tension will increase due to stronger cohesive forces.
C. Surface tension will remain unchanged as it's an intrinsic property.
D. Surface tension will become zero immediately.
View Answer
Option B is correct answer.
Decreasing the temperature, slows down molecular movement of molecules, make the cohesive forces stronger and increases the surface tension.