To determine which of the following statements is incorrect, we will analyze each statement regarding the properties of fluids, specifically focusing on surface tension, viscosity, and the relationship between pressure and velocity.
### Step-by-Step Solution:
1. **Analyze the first statement: "Surface tension of liquids decreases with increase in temperature."**
- This statement is **correct**. As the temperature of a liquid increases, the kinetic energy of the molecules also increases, leading to a decrease in the cohesive forces between the molecules at the surface. Therefore, surface tension decreases with an increase in temperature.
2. **Analyze the second statement: "Viscosity of gases increases with increase in temperature."**
- This statement is **correct**. For gases, as the temperature increases, the molecules move faster and collide more frequently, which leads to an increase in viscosity.
3. **Analyze the third statement: "Viscosity of liquids increases with increase in temperature."**
- This statement is **incorrect**. In liquids, as the temperature increases, the kinetic energy of the molecules increases, which allows them to overcome intermolecular forces more easily. This results in a decrease in viscosity with an increase in temperature.
4. **Analyze the fourth statement: "With increase of pressure, the velocity of liquid flow decreases."**
- This statement is **correct**. According to Bernoulli's principle, when the pressure in a fluid increases, the velocity of the fluid decreases. This relationship is fundamental in fluid dynamics.
### Conclusion:
After analyzing all the statements, we find that the third statement, "Viscosity of liquids increases with increase in temperature," is the incorrect statement.
