Question

When the temperature is raised, the viscosity of the liquid decreases. This is because of (1) decreased volume of solution (2) increase in temperature increases the average kinetic energy of molecules which overcome the attractive force between them (3) decreased covalent and hydrogen bond forces (4) increased attraction between the molecules

Short answer

Option 2: Increase in temperature increases the average kinetic energy of molecules, which overcome the attractive force between them.

Step-by-step solution

- Understand the Problem

We need to determine why the viscosity of a liquid decreases when the temperature is raised.

- Analyze Option 1

Option 1 states that the decreased volume of solution causes the decreased viscosity. Increasing temperature generally causes expansion, not a decrease in volume. So, this option is not correct.

- Analyze Option 2

Option 2 states that the increase in temperature increases the average kinetic energy of molecules, overcoming the attractive forces between them. This would result in the molecules moving more freely, thus reducing viscosity. This option seems logical.

- Analyze Option 3

Option 3 states that decreased covalent and hydrogen bond forces cause the decrease in viscosity. However, the temperature increase affects the kinetic energy rather than directly affecting the bond forces significantly. So, this option is less likely to be correct.

- Analyze Option 4

Option 4 states that increased attraction between the molecules causes the decreased viscosity. Increased attraction would actually increase viscosity, so this option is incorrect.

- Conclusion

Based on the analysis, the most plausible reason why the viscosity decreases with increased temperature is provided by option 2.

Key concepts

kinetic energy

When discussing the viscosity of a liquid, understanding the role of kinetic energy is crucial.
Kinetic energy is the energy that molecules possess due to their motion. The faster the molecules move, the higher their kinetic energy.
When the temperature of a liquid is increased, the molecules gain more energy and move faster.
This increase in molecular movement makes it easier for the molecules to slip past each other, reducing the liquid's viscosity.
Think of it like a dance floor: when it's crowded (low kinetic energy), it's hard to move around.
But as people start dancing faster and with more energy (high kinetic energy), it's easier to navigate through the crowd.
Hence, higher temperatures lead to higher kinetic energy, which in turn lowers the viscosity of the liquid.

molecular attraction

Molecular attraction refers to the forces that hold molecules together.
These forces can be due to different types of bonding, such as van der Waals forces, covalent bonds, or hydrogen bonds.
In the context of liquids, when the temperature is increased, the attractive forces between molecules are easier to overcome.
This happens because the molecules have higher kinetic energy and can move more freely.
Imagine the molecules are like magnets; under low temperature, they stick together tightly.
When the temperature rises, they gain more energy and can overcome the magnetic pull, thus moving more freely.
This reduction in molecular attraction contributes to lowering the viscosity of the liquid.
Understanding this interaction helps explain why a heated liquid flows more easily than a cold one.

temperature effects on liquids

Temperature has a dramatic effect on the behavior of liquids, particularly on their viscosity.
As the temperature increases, the molecules in the liquid gain kinetic energy and move more rapidly.
This increase in movement helps the molecules overcome the intermolecular forces that hold them together.
Consequently, the liquid's viscosity decreases, meaning it flows more easily.
Think of honey: at room temperature, it flows slowly.
Heat it up, and it becomes much more pourable.
The same principle applies to other liquids; higher temperatures generally result in lower viscosity.
Thus, understanding the temperature effects on liquids helps explain everyday phenomena and industrial processes where controlling fluid flow is crucial.