The physical and chemical properties of a solid, in NCERT solutions class 12 chemistry chapter 1 are vital for many reasons. For example, a substance's melting point is necessary to determine its density.

• The physical and chemical properties are determined by the forces that hold its atoms together. In the sodium chloride crystal, ionic bonds have the two elements together.
• The structure of a solid is based on the way it holds together. A solid has a fixed shape and volume and is incompressible.
• Its density is high, and it is incompressible, making it useful for various applications.
• Solids have high melting and boiling points. 

Despite these differences, solids are used to create a variety of objects. They are often used in multiple industries and products and are highly versatile. They are also an excellent tool for research. This article on class 12 chemistry chapter 1 NCERT solutions will describe the different types of solids and how they differ.

Solid State Chemistry is the science of synthesis and properties of solids. This branch of chemistry focuses on studying solids by exploring their composition and chemical bonding. Its goal is to discover random physical properties of interest to engineers and scientists. This science had little impact on engineering in the past, and it was separated from other disciplines. However, in class 12 chemistry chapter 1 NCERT solutions, the discipline has become increasingly important in many fields, including metallurgy and the study of semiconductors, glasses, and polymers.

There are two fundamental states of matter: Amorphous and Crystalline. Each of these states has distinct properties that vary significantly from one another.

The many kinds and subcategories of solid states are covered in detail here.

Crystalline Solid State

The crystalline solid-state is a class of materials that exhibit anisotropy, or changes in physical properties, depending on the direction of the force. In the class 12 chemistry chapter 1 NCERT solutions, it is classified into three types: ionic, covalent, and monatomic.

The latter is characterised by high conductivity. They are insulators with high melting points.

• Non-polar solids are composed of non-polar ions held together by weak dispersion forces. They have a low melting point.
• Polar solids are composed of atoms and molecules that have stronger dipole-dipole interactions.

Quartz, sodium chloride, diamonds, and so forth are examples of such materials.

Characteristic Properties of Crystalline solids 

• Crystalline solids have definite melting and boiling points, generally non-conductive.
• The properties of crystalline substances vary with the direction of the force.
• As the name suggests, crystalline solids have a definite pattern of particles.
• These particles are arranged in regular order and are generally incompressible.
• They have a distinct melting point and cannot be compressed into smaller shapes.
• They will also have a specific temperature because heat breaks all the bonds at once. The simplest examples of crystalline solids are amorphous and cleaved crystalline solids.
• Crystallised solids are materials made up of molecules with regular shapes and sharp edges. They have a unique melting point, the same energy as the liquid they are made of, and similar strength of attraction.
• Owing to this similarity, it is easy to distinguish a crystalline solid from an amorphous one.
• A crystalline material's structure and behaviour are similar to that of a liquid, but amorphous materials do not have the same physical properties.

 Crystalline solids - Types

• Metallic solids
• Ionic solids
• Molecular solids
• Covalent solids

Metallic solids

Metallic components make up their composition. 

• Metals are compounds made up of small non-polar atoms held together by weak forces called London dispersion forces.
• These bonds are fragile, and their pairwise interatomic binding energies are on the order of 1/100th the strength of ionic or covalent bonds.
• These forces are also weakened when the molecules are large and polar so that the metals are difficult to separate into smaller pieces.
• This is why metals are often called ‘solid gold’ and ‘solid silver’.

Metallic solids include metals such as iron (Fe), nickel (Ni), gold (Au), and others.

Ionic solids

Ions are the primary components. Coulombic forces hold them in place, organised in a logical sequence of anions and cations.

• Ionic solids are binary compounds.
• They consist of two or more oppositely-charged ions and have a significant difference in electronegativity.
• Sodium chloride is one example.
• Other ionic solids are referred to by geological names, such as rock salt. These ionic compounds can be studied in both structural and energetic terms. However, it is often unclear what defines an ionic compound.

For instance, NaCl, MgO, and so on.

Molecular solids

Molecular solids are made up of molecules with weak Van der Waals forces.

• They are soft and are insulators, and are typically a mixture of more elements.
• Among the types of molecular solids are organic compounds such as fullerenes and carbon and larger molecules such as halogens and pnictogens.
• The size and structure of these compounds determine whether or not they can be classified as molecularly stable or not.

The molecules that make up molecular solids are the particles that make up the solid. In class 12 chemistry chapter 1 NCERT solutions, the same is subdivided into three categories:

Non-Polar Molecular Solids

In terms of properties, non-polar molecular solids are substances that have a weak dispersion force between their molecules. These solids tend to be soft, and their molecules are held together by powerless London and dispersion forces. While they usually exist in a liquid or gaseous state, some notable exceptions are also. One of the most significant is graphite, a type of molecule with a free fourth electron.

• The melting point of non-conductors and insulators is shallow due to the weak forces.

For instance, F₂, H₂, and so on.

Polar Molecular Solids

Polar molecular compounds have low melting points and good electrical and thermal conductivity.

• These are the most common solids found in electrical applications. Polar molecular compounds have low melting points and high conductivity, making them good conductors.
• These solids are the most often found in electrical applications. 

For instance, HCl, NH₃, and others.

Hydrogen-Bonded Molecular solids

Hydrogen-Bonded Molecular Solids are crystalline compounds based on a network of interconnected atoms. These compounds have high melting and boiling points and are generally poor conductors. One exception to this rule is graphite, a solid at room temperature, but a gas when sublimated. A hydrocarbon molecule has an average of four hydrogen bonds, while a polymer has one or two.

• The solids in question are very tough and durable.
• Their melting values are considerably lower than conductors because they are insulators.
• They are either volatile fluids or soft solids at room temp.

For instance, H₂O, H₂F, and so on.

Covalent Solids

A ‘covalent solid’ is a molecule with a large number of covalent bonds. In these materials, atoms are held together by their covalent bonds, forming a giant molecule. It is impossible to break a covalent solid without breaking many of its other chemical bonds. In this way, as per the class 12 chemistry chapter 1 NCERT solutions, it is different from a ‘solid’ in the traditional sense. It can't melt, either.

• As per the solid state NCERT solutions, according to the structural lattice, they may be either soft or rigid.
• On the configuration of molecules, they may be either conductive or insulated.

For instance, SiO₂, CH₄, and so on are all elements.

Amorphous Solid State

An amorphous Solid State is a substance that lacks the standard shape of atoms or molecules. Amorphous solids (from the Greek amorphous-no form) are composed of particles arranged in an irregular pattern. The configurations of the specific particles are for quick order. That is, periodic organisation and regular order apply only over short distances. It is a supercooled liquid with an infinite volume and a wide melting temperature range.

Although the two types of particles are identical, their physical properties are very different. In solid state chemistry class 12 NCERT solutions, their main distinguishing feature is their incompressibility and lack of long-range regularity. Amorphous solids are highly dense and have a wide melting point range.

• Their placement can be haphazard.
• Amorphous solids are supercooled pseudo-solids. Amorphous solids cleave randomly.
• The melting points are rounded
• The same as liquids, these are isotropic. A rapid succession ensures that all physicochemical characteristics have the same value.

For instance, Polyethylene terephthalate, polymers, crystal glass, and so on.

One common misconception about solid-state class 12 NCERT chemistry is that it is similar to solid-state physics, but this is not the case. Make sure you have these class 12 chemistry chapter 1 NCERT solutions handy. These class 12 chemistry chapter 1 NCERT solutions will help you better understand what was covered in class. 

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Q: What causes solids to be rigid? 

A: The answer lies in the intermolecular forces between constituent particles. These forces keep the atoms in place in a solid, preventing them from moving beyond their fixed positions. This lack of mobility is the main reason why material is rigid. Moreover, it helps to explain the behaviour of objects in everyday life. The following information will help you understand the mechanism of solids.

Q: What are the two fundamental differences between solids and liquids?

A: Solids and liquids have two fundamental differences.

• The main difference between a solid and a fluid is how they are compressed. A solid has a fixed volume, while gas can have an indefinite volume.
• A solid has a fixed volume, and a liquid has no fixed volume. The difference is that solids are close-packed particles that cannot be compressed. On the other hand, a liquid can be poured into any container and remain the same volume.
  
  

Q: What are the main differences between amorphous and crystalline solids?

A: The main differences are as follows:

• The first is in the number of polar groups. These increase the intermolecular forces and increase cohesion between the polymeric chains. On the other hand, moisture content causes the formation of hydrogen bonds between the polymeric chains, reducing the free volume and increasing the Tg.
• Crystallised solids have a higher Tg but are anisotropic. The same is true for amorphous and crystalline solids. 
  
  

Q: Is copper a crystalline or amorphous solid? 

A: It is a Crystalline solid. 

Q: Why is glass classified as a supercooled liquid? 

A: Glass is a supercooled liquid because it is an amorphous solid. Slow-moving materials, such as amorphous solids, are becoming more common. A liquid form is formed since the particles in solids do not move, but a solid crystalline structure is not included in this case. The supercooled liquid is the term used to describe these phenomena.