Problem 84 Why does the viscosity of a liqu... [FREE SOLUTION]

Chapter 10: Problem 84

Why does the viscosity of a liquid decrease as the temperature increases?

Short Answer

Expert verified

The viscosity of a liquid decreases as the temperature increases due to the increase in kinetic energy of the molecules. The enhanced kinetic energy weakens the intermolecular forces, making the liquid less resistant to flow, hence, less viscous.

Step by step solution

Understanding Viscosity

Viscosity refers to the resistance of a fluid to flow. In more simple words, it is the 'thickness' or 'stickiness' of a fluid. High viscosity means the fluid is thick and sticky and flows slowly, like honey. On the other hand, low viscosity fluids flow easily and quickly, like water.

Effect of Temperature on Molecular Activity

As the temperature of a liquid increases, the kinetic energy of its molecules also increases. This enhanced energy makes the molecules move faster and more chaotically.

Temperature and Viscosity Relation

When the temperature increases, the molecules in a fluid move faster. Due to this enhanced kinetic activity, the intermolecular forces of attraction become weaker, making it easier for the molecules to slip past each other. Hence, as temperature increases, a liquid's viscosity decreases.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Kinetic Energy

Kinetic energy is the energy that an object possesses due to its motion. In the context of liquids, molecules are in constant motion, and this movement is related to their kinetic energy.

Higher kinetic energy means that the molecules move faster. When you increase the temperature of a liquid, the kinetic energy of its molecules also increases. This increased energy causes them to move more vigorously. Here's how it affects viscosity:

Faster-moving molecules collide more frequently and with greater energy.
The increased motion disrupts the ordered arrangement of molecules, leading to less resistance to flow.
Greater kinetic energy can overcome strong intermolecular forces more easily.

So, in essence, an increase in kinetic energy reduces the liquid's viscosity, allowing it to flow more readily.

Intermolecular Forces

Intermolecular forces are the forces of attraction between molecules. These forces play a significant role in determining the physical properties of liquids, such as viscosity.

Stronger intermolecular forces make it more difficult for molecules to slide past each other, which increases viscosity. However, the interplay of kinetic energy can weaken these forces:

Kinetic energy increases molecular motion, disrupting intermolecular attractions.
As molecules shake free from each other's grip, the liquid becomes less viscous.
Intermolecular forces clash with kinetic energy; higher energy usually wins out.

The balance between these forces and kinetic energy is what defines the fluid's behavior, particularly when temperature changes.

Temperature Effects on Liquids

Temperature has a profound impact on the properties of liquids. When a liquid's temperature rises, multiple changes occur at the molecular level:

Increased kinetic energy drives molecules apart.
Weaker intermolecular forces lead to easier flow.
Less viscous, more fluid behavior is observed.

In the case of viscosity, higher temperatures provide energy to the molecules, enhancing their ability to overcome interactions that hinder movement. As a result, the effect of increased temperature is quite significant in decreasing a liquid's viscosity.

This is why when you heat a fluid, like syrup, it becomes easier to pour; its molecules are energized and the resistance to flow is much lower than when it was cold.

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91影视

Why does the viscosity of a liquid decrease as the temperature increases?

Short Answer

Step by step solution

Understanding Viscosity

Effect of Temperature on Molecular Activity

Temperature and Viscosity Relation

Key Concepts

Kinetic Energy

Intermolecular Forces

Temperature Effects on Liquids

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