ChemistryChapter 5: States and Phases of Matter

5.3.3 Liquid Crystals and Their Uses in Daily Life

Liquid Crystals:

This topic explains what liquid crystals are, how they were discovered, their properties, and their uses in daily life.

Definition

Liquid Crystals: The liquid crystalline state between the melting temperature and the clearing temperature is called liquid crystals.

Main Idea

Pure liquids have sharp melting points, and at their melting point, the temperature remains constant. Generally, when solids are heated, they are converted into liquids. In 1888, Frederick Reinitzer discovered a universal property during a study of cholesteryl benzoate, an organic compound. When this compound is heated, it turns into a milky liquid at 145°C and turns into a clear liquid at 179°C. When cooled, the reverse occurs. The turbid liquid state is called liquid crystals.

Core Concept

Liquid crystals are an intermediate state between solid crystals and clear liquids.
They have properties of both crystals (optical properties) and liquids (fluidity).
They are formed by long rod-like molecules.
On the basis of the order of molecules, liquid crystals are classified as nematic, smectic, and cholesteric.

Detailed Explanation

Discovery of Liquid Crystals

In 1888, Frederick Reinitzer discovered a universal property during a study of cholesteryl benzoate, an organic compound.
When this compound is heated, it turns into a milky liquid at 145°C and turns into a clear liquid at 179°C.
When cooled, the reverse occurs.
The turbid liquid state is called liquid crystals.

Properties of Liquid Crystals

There are many crystalline solids which melt to a turbid liquid and then to a clear liquid phase.
The turbid liquid phase can flow and has properties of liquids like viscosity and surface tension.
It is to be noted that molecules of these turbid liquids have some degree of order and resemble crystals in properties like optical properties.
The liquid crystalline state between the melting temperature and the clearing temperature is called liquid crystals.
Liquid crystals are always isotropic, while crystalline solids may be isotropic or anisotropic.

Solid crystal ⇌ liquid crystal ⇌ clear liquid

Long rod-like molecular substances make these types of liquid crystals.
These molecules are oriented in random directions in the normal liquid phase, and in liquid crystal form, they are in order.
On the basis of the order of molecules, the liquid crystals are nematic, smectic, and cholesteric.
The liquid crystal is intermediate between solid crystal and clear liquid; its properties are also between crystal properties and those of isotropic liquids.
Liquid crystals have properties of crystals like optical properties and have the fluidity of liquids.

Did you understand this topic?

Your answer is saved with your learning record. It does not mark the topic as mastered.

Ask Tutor about this Open in Topics

Same supplied content as this Notes page (shared canonical source).

Main Idea

Core Concept

Liquid crystals are an intermediate state between solid crystals and clear liquids.

They have properties of both crystals (optical properties) and liquids (fluidity).

They are formed by long rod-like molecules.

On the basis of the order of molecules, liquid crystals are classified as nematic, smectic, and cholesteric.

Detailed Explanation

Discovery of Liquid Crystals

In 1888, Frederick Reinitzer discovered a universal property during a study of cholesteryl benzoate, an organic compound.

When this compound is heated, it turns into a milky liquid at 145°C and turns into a clear liquid at 179°C.

When cooled, the reverse occurs.

The turbid liquid state is called liquid crystals.

Properties of Liquid Crystals

There are many crystalline solids which melt to a turbid liquid and then to a clear liquid phase.

The turbid liquid phase can flow and has properties of liquids like viscosity and surface tension.

It is to be noted that molecules of these turbid liquids have some degree of order and resemble crystals in properties like optical properties.

The liquid crystalline state between the melting temperature and the clearing temperature is called liquid crystals.

Liquid crystals are always isotropic, while crystalline solids may be isotropic or anisotropic.

Solid crystal ⇌ liquid crystal ⇌ clear liquid

Long rod-like molecular substances make these types of liquid crystals.

These molecules are oriented in random directions in the normal liquid phase, and in liquid crystal form, they are in order.

On the basis of the order of molecules, the liquid crystals are nematic, smectic, and cholesteric.

The liquid crystal is intermediate between solid crystal and clear liquid; its properties are also between crystal properties and those of isotropic liquids.

Liquid crystals have properties of crystals like optical properties and have the fluidity of liquids.