matter-solid-featured

Solids – The State of Matter

Definition of Solids

“Solids are those compounds which are rigid, tough, have a definite shape and definite volume”.

  • The atoms, ions, and particles that make up a solid are closely packed.
  • They are held together by strong cohesive forces.
  • The constituent atoms, ions, or molecules of solids can not move at random.
  • There exists a well-ordered arrangement in solids.
Types of Solids

Solids can be classified based on the regular plans of constituent atoms, ions, or molecules. There are two kinds of solids in this regard.

(i) Crystalline Solids

Those solids in which atoms, ions or molecules are arranged in a definite3-dimensional pattern are called crystalline solids. This repeating regular geometrical pattern of the structure extends 3- dimensionally.

Crystalline-Solids

(ii) Amorphous Solids

All solids are not crystalline. The word amorphous means shapeless.

” Amorphous substances are those whose constituent atoms, ions, or molecules do not possess a regular orderly arrangement”.

The best examples are glass, plastics, rubber, glue, etc. These compounds have solid-state properties and virtually total maintenance of shape and volume. However, they do not have an ordered crystalline state.

Numerous crystalline solids can be changed into amorphous solids by melting them and then cooling the molten mass rapidly. In this way, the constituent particles do not find time to organize themselves.

A long-range regularity does not exist in amorphous solids but they can possess little areas of organized arrangements. These crystalline parts of otherwise amorphous solids are referred to as crystallites.

Amorphous solids don’t have sharp melting points that is why particles of glass soften over a temperature range and can be moulded and blown into numerous shapes. They do not possess definite heats of fusion.

Properties of Crystalline Solids
Geometrical shape

All the crystalline solids have a definite, unique geometrical shape due to the definite and orderly plan of atoms, ions or particles in the three-dimensional area. For a given crystal, the interfacial angles, at which the surfaces converge, are constantly the same no matter in which shape they are grown. The faces and angles stay particular even when the material is ground to a fine powder.

Melting Points

Crystalline solids have sharp melting points and can be identified from their definite melting points.

Cleavage Planes

Whenever the crystalline solids are broken, they do so along definite planes. These planes are called the cleavage planes and they are inclined to one another at a particular angle for an offered crystalline solid. The value of this angle differs from one solid to another solid.

Anisotropy

A few of the crystals reveal variation in physical properties relying on the direction. Such properties are called anisotropic properties and the phenomenon is referred to as anisotropy. The physical properties of crystalline solids like refractive index, coefficient of thermal expansion, electrical and thermal conductivities are in some cases anisotropic in nature for some crystals.

The variation in these properties with direction is because of truth that the orderly plan of the particles in crystalline solids is different in different instructions. For example, the electrical conductivity of graphite is greater in one direction than in another.

Further Reading:  Trends in Periodic Table [Atomic Radius, Ionization Energy, Ionic Radius and More]

In fact, electrons in graphite are mobile for electrical conduction parallel to the layers. For that reason, its conductivity in this direction is far much better than perpendicular to the other directions. Likewise, cleavage itself is an anisotropic behaviour.

Anisotropy

Symmetry

The repetition of faces, angles, or edges when a crystal is rotated by 360 ° along its axis is called symmetry. This is a crucial property of the crystal and there are different kinds of symmetry elements discovered in crystals like the center of symmetry, the plane of symmetry and axis of symmetry, and so on.

Habit of a Crystal

The shape of a crystal in which it normally grows is called the habit of a crystal. Crystals are normally acquired by cooling the saturated option or by slow cooling of the liquid compound. These are formed by growing in different directions.

If the conditions for growing a crystal are kept, then the shape of the crystal always remains the same. If the conditions are altered the shape of the crystal may change. For instance, a cubic crystal of NaCl ends up being needle-like when 10% urea is present in its solution as an impurity.

Isomorphism

Isomorphism is the phenomenon in which two different substances exist in the very same crystalline type. These different compounds are called isomorphs of each other.

A crystalline type is independent of the chemical nature of the atoms and depends just on the variety of atoms and their method of combination.

Primarily the ratio of atoms in numerous compounds is such that isomorphism is possible. Their physical and chemical properties are rather different from each other. Anyway, isomorphic substances take shape together in all proportions in uniform mixtures. The following examples tell us the nature of the compound, their crystalline kinds, and the ratio of their atoms.

The structures of the negatively charged ions like NO3-1 and CO32-, are the same. Similarly shapes of SO42- and CrO42- are also alike. CO32-, and NO3-1are triangular planar units, while SO42and CrO42-are both tetrahedral.

Polymorphism

Polymorphism is a phenomenon in which a compound exists in more than one crystalline form. That compound which exists in more than one crystalline form is called a polymorphic, and these forms are called polymorphs, and these forms are called polymorphs of each other.

Polymorphs have exact same chemical properties, but they differ in the physical properties. The difference in physical properties is due to the different structural arrangements of their particles.

The following substances are very important polymorphs.

Polymorphism

 

Allotropy

The existence of an element in more than one crystalline form is called allotropy and these kinds of the element are called allotropes or allotropic kinds. Sulphur, phosphorus, carbon and tin are some major examples of elements which reveal allotropy.

Allotropy

Transition Temperature

It is that temperature at which two crystalline forms of the same substance can co-exist in balance with each other. At this temperature level, one crystalline type of substance changes to another. Above and below this temperature, only one type exists.

A few examples for those substances which show allotropy and have a transition temperature are listed below.

Further Reading:  Reactions of Lipids with MCQs + FAQs

(i) Grey Tin (cubic)⇌White tin (Tetragonal)

13.2C

(ii) Sulphur S8 (rhombic)⇌Sulphur S8(monoclinic)

95.5C

(iii) KNO3 (orthorhombic) ⇌ KNO3(rhombohedral)

123C

MCQs about Solids – The State of Matter

  1. What is the defining characteristic of solids?
    • A. Variable shape
    • B. Indefinite volume
    • C. Rigid and definite shape
    • D. No cohesive forces

    Answer: C. Rigid and definite shape

  2. Which type of solids have atoms, ions, or molecules arranged in a definite 3-dimensional pattern?
    • A. Amorphous Solids
    • B. Crystalline Solids
    • C. Glassy Solids
    • D. Liquid Solids

    Answer: B. Crystalline Solids

  3. What does the term “amorphous” mean in the context of solids?
    • A. Rigid
    • B. Shapeless
    • C. Crystal clear
    • D. Symmetrical

    Answer: B. Shapeless

  4. Which of the following is an example of an amorphous solid?
    • A. Diamond
    • B. Glass
    • C. Quartz
    • D. Ruby

    Answer: B. Glass

  5. What is the key characteristic of cleavage planes in crystalline solids?
    • A. Random orientation
    • B. Definite melting points
    • C. Planes of breakage
    • D. Symmetrical arrangement

    Answer: C. Planes of breakage

  6. Anisotropy in crystals refers to:
    • A. Variable melting points
    • B. Variation in physical properties with direction
    • C. Amorphous structure
    • D. Random arrangement of atoms

    Answer: B. Variation in physical properties with direction

  7. Which property is a result of symmetry in crystals?
    • A. Melting point
    • B. Cleavage planes
    • C. Symmetry
    • D. Geometrical shape

    Answer: C. Symmetry

  8. What is the habit of a crystal?
    • A. Regular shape
    • B. Growing in different directions
    • C. Changing conditions
    • D. Specific geometrical shape

    Answer: B. Growing in different directions

  9. Isomorphism in crystalline solids involves:
    • A. Same chemical nature
    • B. Different crystalline forms
    • C. Different substances with similar structures
    • D. Lack of symmetry

    Answer: C. Different substances with similar structures

  10. Polymorphism is characterized by:
    • A. Same physical properties
    • B. Different chemical properties
    • C. Same crystalline form
    • D. Different crystalline forms

    Answer: D. Different crystalline forms

  11. Which term refers to the existence of an element in more than one crystalline form?
    • A. Isomorphism
    • B. Polymorphism
    • C. Allotropy
    • D. Symmetry

    Answer: C. Allotropy

  12. What is the transition temperature in the context of crystalline forms?
    • A. Temperature for melting
    • B. Temperature for sublimation
    • C. Temperature for co-existence of forms
    • D. Critical temperature

    Answer: C. Temperature for co-existence of forms

  13. Which substance shows allotropy and has a transition temperature between grey and white tin?
    • A. Sulphur
    • B. Phosphorus
    • C. Carbon
    • D. Tin

    Answer: D. Tin

  14. What is the transition temperature for the allotropy of Sulphur (S8)?
    • A. 95.5°C
    • B. 123°C
    • C. 13.2°C
    • D. 60°C

    Answer: B. 123°C

  15. Which type of solid has a definite, unique geometrical shape due to a well-ordered arrangement of particles?
    • A. Liquid Solids
    • B. Random Solids
    • C. Crystalline Solids
    • D. Glassy Solids

    Answer: C. Crystalline Solids

 

Frequently Asked Questions (FAQs) – Solids: The State of Matter

Definition of Solids:

Q1: What is the definition of solids?

  • Solids are compounds that are rigid, tough, and have a definite shape and volume.

Q2: How are the atoms, ions, and particles arranged in solids?

  • They are closely packed and held together by strong cohesive forces, with a well-ordered arrangement.

Types of Solids:

Q3: What are the two main types of solids?

  • Crystalline Solids and Amorphous Solids.

Q4: How can we distinguish crystalline solids from amorphous solids?

  • Crystalline solids have a repeating 3-dimensional pattern, while amorphous solids lack a regular orderly arrangement.
Further Reading:  Hard & Soft Water - Ways to Softening of Hard Water

Q5: Can crystalline solids be transformed into amorphous solids?

  • Yes, by melting them and rapidly cooling the molten mass.

Properties of Crystalline Solids:

Q6: What gives crystalline solids a definite, unique geometrical shape?

  • The definite and orderly plan of atoms, ions, or particles in the three-dimensional space.

Q7: How can we identify crystalline solids?

  • They have sharp melting points.

Q8: What are cleavage planes in crystalline solids?

  • Cleavage planes are the definite planes along which crystalline solids break, inclined at specific angles.

Q9: What is anisotropy in the context of crystalline solids?

  • Anisotropy refers to the variation in physical properties depending on the direction in crystals.

Miscellaneous:

Q10: Can amorphous solids exhibit a sharp melting point?

  • No, amorphous solids do not have sharp melting points.

Q11: What is the habit of a crystal?

  • The habit of a crystal refers to the shape in which it normally grows.

Q12: What is isomorphism in crystalline solids?

  • Isomorphism is when two different substances exist in the same crystalline form.

Q13: How is polymorphism different from isomorphism?

  • Polymorphism is when a compound exists in more than one crystalline form, whereas isomorphism involves different substances in the same form.

Q14: What is allotropy?

  • Allotropy is the existence of an element in more than one crystalline form.

Q15: What does transition temperature signify in crystalline forms?

  • It is the temperature at which two crystalline forms of the same substance can co-exist in balance with each other.

 

Wrapping up Solids

This tutorial explores the diverse aspects of solids, providing a comprehensive understanding of their definition, types, and properties.

1. Definition of Solids:

  • Solids are compounds with a definite shape and volume, characterized by rigidity and toughness.
  • Constituent atoms, ions, or molecules are closely packed and held together by strong cohesive forces, resulting in a well-ordered arrangement.

2. Types of Solids:

  • Crystalline Solids (2.1):
    • Atoms, ions, or molecules are arranged in a definite 3-dimensional pattern, exhibiting a repeating geometrical structure.
  • Amorphous Solids (2.2):
    • Lack a regular orderly arrangement, and their particles do not possess a specific shape.

3. Properties of Crystalline Solids:

  • 3.1) Geometrical Shape:
    • Crystalline solids have a definite, unique geometrical shape due to the orderly arrangement of particles.
  • 3.2) Melting Points:
    • Sharp melting points distinguish crystalline solids.
  • 3.3) Cleavage Planes:
    • Crystalline solids break along definite planes with specific angles.
  • 3.4) Anisotropy:
    • Variation in physical properties based on direction, resulting from different particle arrangements.
  • 3.5) Symmetry:
    • Symmetry involves the repetition of faces, angles, or edges when a crystal is rotated.

4. Habit of a Crystal:

  • The shape in which a crystal normally grows, influenced by conditions during formation.
  • Changing conditions can alter the crystal’s shape.

5. Isomorphism:

  • Different substances existing in the same crystalline form, independent of the chemical nature of atoms.

6. Polymorphism:

  • A compound existing in more than one crystalline form, exhibiting the same chemical properties but differing in physical properties.

7. Allotropy:

  • The existence of an element in more than one crystalline form; examples include sulfur, phosphorus, carbon, and tin.

8. Transition Temperature:

  • The temperature at which two crystalline forms of the same substance coexist in balance, leading to a transformation between forms.

Conclusion:

This tutorial provides a thorough exploration of solids, covering their definition, types, and various properties. Understanding these concepts is crucial for comprehending the behavior and characteristics of different solid states in nature.