Problem 1 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is not a feature of solids? (a) definite mass and volume (b) frequent fluidity (c) rigidity (d) definite shape

Step-by-Step Solution

Answer

Option (b) 'frequent fluidity' is not a feature of solids.

Step 1: Understand Features of Solids

Solids are characterized by having a definite shape and volume, a definite mass, and rigidity. These features stem from the fixed position of the molecules and strong intermolecular forces.

Step 2: Identify Contradictory Features

Consider the property of fluidity, which means the ability to flow. Solids do not exhibit fluidity as their molecules are fixed in a rigid structure. Fluidity is a property of liquids and gases, not solids.

Step 3: Analyze Given Options

Option (a) 'definite mass and volume,' option (c) 'rigidity,' and option (d) 'definite shape' are all features of solids. Option (b) 'frequent fluidity' contradicts the features of solids, as they do not flow like liquids or gases.

Key Concepts

Rigidity

Rigidity is a hallmark characteristic of solids. It refers to the ability of a substance to resist deformation when external forces are applied. In the case of solids, the particles are tightly packed in a fixed arrangement. This fixed positioning results in a strong resistance to changes in shape or volume.
The firm structure of solids is due to the strong intermolecular forces that firmly hold the constituent particles in place. For example, when you try to bend a metallic rod or attempt to compress a book, their rigid structures prevent shape alteration.

• Solids maintain their form under stress.
• Particles in solids vibrate only in fixed positions.
• Increased rigidity compared to liquids and gases.

Rigidity is essential in many applications where maintaining shape and resisting outside forces are crucial, like in construction materials and metal tools.

Definite Shape

A defining feature of solids is their definite shape. Unlike liquids and gases, which can flow and take the shape of their container, solids maintain a consistent form.
This characteristic is due to the fixed positions of its particles. Each particle in a solid is bound to its neighbors by strong intermolecular forces. These particles vibrate slightly but remain in their fixed positions, helping solids keep a definite shape.

• Always retains shape regardless of container.
• Cannot expand to fill container like liquids or gases.
• Useful in applications requiring precise dimensions, like manufacturing parts.

Consider a sugar cube. No matter where you place it, the cube retains its shape. This quality is why solids are essential in creating and maintaining structures and forms.

Fluidity

Fluidity is the property of a substance to flow easily, conforming to the shape of its container. Solids lack this characteristic because their particles cannot move freely past one another.
In contrast, liquids and gases have particles that can move more freely, allowing them to flow and adapt to different shapes. This fundamental difference separates the behavior of solids from other states of matter.

• Solids are non-fluid, meaning they cannot flow or change shape easily.
• Fluid substances (liquids and gases) can occupy the shape of their container.
• Fluidity is a crucial factor in differentiating between different states of matter.

For example, when you pour water into a cup, it flows to fit the shape of the cup's interior. Solids, however, like a marble, will stay in the same shape, regardless of the container's form.