Final answer:
The viscosity of a liquid decreases with temperature due to reduced cohesive forces, while the viscosity of a gas increases with temperature due to increased collisions between atoms and molecules.
Step-by-step explanation:
The viscosity of a liquid decreases with an increase in temperature because higher temperature reduces the effects of cohesive forces.
When the temperature increases, the kinetic energy of the molecules also increases.
This increased kinetic energy disrupts the intermolecular forces, allowing the molecules to move more freely and reducing the resistance to flow.
On the other hand, the viscosity of a gas increases with temperature because increased gas temperature creates more collisions between atoms and molecules.
These collisions contribute to the overall resistance to flow, resulting in higher viscosity.