Question

Why does the viscosity of a liquid decrease with increasing temperature?

Short answer

The viscosity of a liquid decreases with increasing temperature because, as the temperature increases, the kinetic energy of the particles also increases. This reduces the ability of the intermolecular forces to hold the particles together, resulting in reduced viscosity, i.e., increased flowability.

Step-by-step solution

Understand the concept of viscosity

Viscosity refers to a fluid's resistance to deformation or flow. It is caused by the intermolecular forces of attraction present in fluid substances that oppose the relative motion of the particles. In simple terms, the stronger the intermolecular forces, the higher the viscosity.

Understand the effect of temperature on kinetic energy

As the temperature increases, the kinetic energy of the particles also increases. This is because temperature is a measure of the average kinetic energy of the particles in a substance. Therefore, higher temperatures cause the particles to move faster.

Clarify the relationship between temperature, kinetic energy, and viscosity

The faster motion at higher temperatures increases the kinetic energy of the particles and reduces the effective power of the intermolecular forces, thereby reducing the viscosity. This is because the intermolecular forces of attraction cannot hold the high-energy, rapidly moving particles as effectively, leading to reduced resistance to flow.