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Under this topic is the most important numerical of the density of a solid. It is asked in one form or the other every year. Hence, this topic is very important from an exam point of view. Read the entire article to understand the basics of amorphous and crystalline Solids and solve frequently asked previous year questions. One of the states of matter is solid-state. We learned in elementary school that matter occurs in three states: solid, liquid, and gas. However, as we move through the grades, the principles become more advanced, and there are more things to understand. In this article, we'll look at the definition of solid-state in a wider sense and learn all of the words that go along with it, such as properties and solid forms.
| Table of Contents |
Key Terms: Solids, Crystalline solids, Amorphous solids, State of matter, Liquid, Gas, Atoms, Non-crystalline solid
Types of Solid States
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Solids are categorized into two states based on the arrangement of constituent particles:
- Amorphous Solids
- Crystalline Solids
Arrangement of Constituent Particles
Amorphous Solids
Amorphous solids are solids in which the constituent particles of matter are organized in a random pattern. It is a non-crystalline solid in which the atoms are not arranged in a regular pattern in the solid lattice. Amorphous solids, in other words, are materials that lack a definite ordered structure of atoms and molecules. The majority of solids are amorphous and are used in a variety of industries. Glass, which is commonly used in the automotive industry, is one of the most popular examples of amorphous solids.
Examples: Metallic Glass, Rubber, Plastics, Glass, Polymers, Gel, etc.
Amorphous Solids' Properties
The following properties of an amorphous solid are depicted:
- Amorphous solids soften progressively over a temperature spectrum and can be molded into various shapes when heated.
- Amorphous solids are pseudo solids or supercooled liquids, which means they have a sluggish flow rate. If you look at the glass panes that are attached to the windows of old houses, you'll notice that they are slightly thicker at the bottom than at the top.
- Amorphous solids have an irregular form since their constituent particles are not arranged in a definite geometry.
- When amorphous solids are cut with a sharp-edged instrument, irregular surfaces result.
- Because of the irregular arrangement of the particles, amorphous solids do not have definite heat of fusion.
- Because of the irregular arrangement of particles, amorphous solids are isotropic, which means that the value of any physical property will be the same in any direction.
Uses of Amorphous Solids
- Amorphous solids have a wide range of uses, including the following:
- Rubber is primarily used in the production of tires, boots, chains, and camp fabric, as well as as a raw material in a variety of industries.
- Glass is commonly used in packaging (food cans, cosmetics boxes, and soft-drink bottles), tableware (utensils), and building construction (windows, lighting, and shelves), among other applications.
- The best photovoltaic material for converting sunlight into electricity is amorphous silicon.
- Polymer is used in the manufacture of pipes, medications, and as a raw material in many factories.
Crystalline Solids
Crystalline Solids are solids in which the constituent particles of matter are structured and organized in a particular way. The composition of these solids contains crystals, each of which has a distinct geometry. Furthermore, crystalline solids are the most stable type of solids due to their low potential energy. Almost all solids are known as crystalline solids, including metallic elements (iron, silver, and copper) as well as non-metallic elements (Phosphorus, Sulphur, and iodine). Crystalline solids are often formed by many compounds such as sodium chloride, zinc sulphide, and naphthalene.
Examples: Diamonds, Calcite, Quartz, Mica, Sugar, etc.
Crystalline Solid’s Properties
- Crystalline solids have a distinct melting point and begin to melt at a certain temperature.
- The shape of crystalline solids is described, with typical particle arrangements.
- They have cleavage properties, which means that when sliced with the edge of a sharp tool, they break into two parts, leaving smooth and simple surfaces.
- Crystalline solids are anisotropic, which means that when physical properties like electrical resistance or refractive index are calculated in different directions in the same crystal, they display different values.
- Since crystalline solids do not flow like pseudo solids, they are also known as True Solids.
Uses of Crystalline Solids
- Crystalline solids have a wide range of uses, including the following:
- The most excellent example of crystalline solids is diamond, which is commonly used in the development of beautiful jewelry.
- Quartz is widely used in the production of watches and clocks.
- In many industries, crystalline solids are used as raw materials.
The video below explains this:
Amorphous and Crystalline Solids Detailed Video Explanation:
Read More:
| Related Articles | ||
|---|---|---|
| Physical and Chemical Classification Of Matter | Imperfections in Solids | Crystal Lattices and Unit Cells |
| Schottky Defect | Magnetic Properties | Frenkel Defect |
Types of Crystalline Solids
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Crystalline solids are divided into four groups based on the presence of intermolecular forces or chemical bonding. They are, indeed:
- Molecular Solids
- Ionic solids
- Metallic solids
- Covalent solids
- Molecular solids : The constituent particles of molecular solids are molecules. In general, molecular solids are insulators and soft in nature. Molecular solids have a very low density. Molecular solids are further categorized into three types based on the nature of molecules:
- Non-polar Molecular Solids
- Polar Molecular Solids
- Hydrogen-bonded Molecular Solids
- Ionic Solids : Ions are the constituent particles in ionic solids. These are formed by strong Coulombic forces arranging cations and anions. These are fragile and hard in nature. In the solid state, ionic solids are insulators, but in the molten and aqueous states, they are conductors. Their melting point is extremely high.
- Example: NaCl, MgO, ZnS, CaF2 etc.
- Metallic Solids : In a sea of delocalized electrons, positive metal ions exist. These electrons are distributed uniformly throughout the crystal. They are responsible for high electrical and thermal conductivity due to the presence of free and mobile electrons. In both the solid and liquid states, they are conductors. These solids have a hard physical nature, but they are malleable and ductile. In comparison to ionic solids, they have a higher melting point.
- Examples: Fe, Cu, Ag, Mg, etc.
- Covalent Solids : A broad variety of non-metal crystalline solids shape a giant molecule or large molecules by forming covalent bonds between neighboring atoms in the crystal. These solids, which are carbon isotopes, are hard like diamond and soft like graphite. They are insulators, like diamonds, but due to free electrons, they conduct electricity and act as a conductor in the case of graphite.
Crystalline vs. Amorphous Solids
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The following table summarises the differences between Crystalline and Amorphous Solids:
| Point of difference | Crystalline Solids | Amorphous solids |
|---|---|---|
| Arrangement of atoms | Crystalline solids have a definite and normal geometry, and their constituent particles have both long-range and short-range order. | The constituent particles in amorphous solids are arranged irregularly. They lack some kind of definite geometry and have a lower range order. |
| Melting point | The melting points of crystalline solids are typically strong and distinct. | The melting points of amorphous solids are not sharp. |
| Shape of solid | As crystals are formed, their external forms tend to be normal. | When amorphous solids are shaped, they have no external regularity. |
| Edges | When cut with a knife, crystals appear to have a clean surface. | The cut-edges of amorphous solids are normally irregular. |
| Heat of fusion | They move through a definite fusion heat. | There is no clear heat of fusion in amorphous solids. |
| Compression | Due to their rigid nature, the mild distorting forces cannot bend the Crystalline solids. | The rigidity of amorphous solids, on the other hand, is absent. Bending or compressing them may be used to achieve the deformation. |
| Nature of solid | Crystalline solids are known to be true solids. | Supercooled liquids or pseudo solids are classified as amorphous solids. |
| Isotropy/Anisotropy | Anisotropism is common in crystalline solids. | Isotropism is common in amorphous solids. |
Also Read:
Things to Remember
- Solids are of two types - Crystalline and Amorphous solids.
- Crystalline solids are hard and possess a definite geometrical shape.
- Amorphous solids are soft and do not possess a definite shape.
- Crystalline solids have a definite melting point whereas amorphous solids do not have a fixed melting point and soften over heating.
- Metals, diamonds, graphite are some of the example of crystalline solids. Glass is an example of amorphous solids.
- Crystalline solids are isotropic and amorphous solids are anisotropic.
Sample Questions
Ques. (a) The density, atomic mass and edge length of an element are 11.5 g/cm3 ,93 g/mol and 300 pm respectively. Which type of unit cell does it form?
(b)Elucidate any two differences between amorphous and crystalline solids. (Delhi, 2017)(3 Marks)
Ans. (a) According to the question, Molecular Mass (M)=93 g/mol ρ = 11.5 g/cm3 Edge length
(a) = 300 pm = 300/10-8cm From the formula : Putting values in the above equation, Z = 2.01 Hence, the number of atoms in a single unit cell is 2. So the given cell is a BCC cell.
(b)
| Point of difference | Crystalline Solids | Amorphous solids |
|---|---|---|
| Arrangement of atoms | Crystalline solids have a definite and normal geometry, and their constituent particles have both long-range and short-range order. | The constituent particles in amorphous solids are arranged irregularly. They lack some kind of definite geometry and have a lower range order. |
| Melting point | The melting points of crystalline solids are typically strong and distinct. | The melting points of amorphous solids are not sharp. |
Ques. (a) An element has a bcc lattice with a cell edge of 288 pm. Find out the molar mass if its density is 7.2 g/cm3. (All India compartment 2017)(3 marks)
(b) “Crystalline solids are anisotropic in nature” Explain. (3 Marks)
Ans: We have been given that: a = 288 pm or 288 x 10-10 cm Z = 2, ρ = 7.2 g/cm3 M = ? From the formula : z=\(\frac{{\rho}*a^3*Na}{M}\), substituting the values, M = 51.8 g/mol
(b) Anisotropy means that in case of crystalline solids, propertiesuch as refractive index, density,etc have different values when viewed from different angles. This is because of their regular, repetitive structure in different directions.
Ques. (a) Silver crystallises in an fcc lattice. If the edge length of a cell is 4.07 × 10-8 cm and the density of the crystal is 10.5 g cm-3, find out the atomic mass of silver. (All India Compartment, 2015)(3 Marks)
(b) Give reason : Crystalline solids are anisotropic in nature
Ans: (a) We have been given that: a = 4.07 x 10-8 cm Z = 4, ρ = 10.5 g/cm3 M = ? Substituting the values in the formula z=\(\frac{{\rho}*a^3*Na}{M}\), M = 106.6 g/mol
(b) Crystalline solids are anisotropic because of their regular, repetitive structure in different directions.
Ques. (a) Classify these solids : Sodium sulphate, Hydrogen based on the nature of intermolecular forces.
(b)An element forms a bcc lattice, whose cell edge is 400 pm. What is its density, given that 500 g of this element contains 2.5 × 1024 atoms. (Delhi compartment 2017) (3 marks)
Ans: (a) Sodium Sulphate is an Ionic Solid. Hydrogen is a non polar molecular solid.
(b) We have been given that: a = 400 pm = 400 x 10-10 cm Z = 2 (bcc lattice) Since 500 g contains 2.5 × 1024 atoms, in 6.022 × 1023 atoms, the weight is 120.44 g. Hence M=120.44 g/mol Substituting the values in the formula z= \(\frac{{\rho}*a^3*Na}{M}\),
ρ=6.25 g/cm3
Ques.(a) Classify the given solids based on the nature of intermolecular forces: Benzene, Silver (All India 2017)
(b)An element has a bcc crystal lattice. Its cell edge is 500pm and density is 7.5g cm-3. How many atoms are present in 300 g of the element? (All India 2015)(3 marks)
Ans: (a) Benzene is a nonpolar molecular solid. Silver is a metallic solid.
(b) Since the lattice is bcc, Z=2. As stated in the question, a = 500 pm = 500 x 10-10 cm, ρ= 7.5g cm-3. Substituting the values in the formula z= \(\frac{{\rho}*a^3*Na}{M}\), M=282.28 g/mol. Hence, 282.28 g of this element contains 6.02x1023 atoms. From unitary method, 300 g of the element will contain 6.40 × 1023 atoms.
Ques. (a) Iron forms a bcc unit cell. Its cell dimension is 286.65 pm. The density of iron is 7.874 g cm-3. Calculate the avogadro number from this information. (M of Fe = 55.84 g mol-1). (All India compartment 2014)(3 marks) (b)Give examples of : (i) Molecular solid, (ii)ionic solid
Ans: (a) According to the question, a = 286.65 pm = 286.65 × 10-10, d = 7.87 g cm-3, M = 56 g mol-1 Z = 2, NA = ? Applying the formula : z= \(\frac{{\rho}*a^3*Na}{M}\), Avogadro’s number = 6.023x1023
(b) (i) Iodine (ii) Sodium chloride (NaCl)
Ques. (a)The density of copper is 8.95 g cm-3. It has a face centred cubic structure. What is the radius of copper atom (Compartment Delhi 2014) (3 marks)
(b)Differentiate metallic and ionic solids on the basis of electrical conductivity
Ans: (a)
(b) In case of metallic solids, the conductivity is due to free electrons. In case of ionic solids, the conductivity is due to ions.
Ques. Niobium solid has a bcc structure. Its density is 8.55 g cm-3. Calculate atomic radius of niobium. (M=93 u) (Delhi compartment 2013)(3 marks)
Ans: According to the question, = 7.87 g cm-3, M = 56 g mol-1 ρ= 8.55 g/cm3 , Z = 2, NA = 6.023x1023 , a=?
a = (36.1)⅓ x 102 pm = 330.4 pm.
For bcc, r=34a = 143.1 ρm
Ques. (a) There are a few glass objects, which when recovered from ancient monuments look milky rather than transparent. Why? (b) Copper has a fcc unit cell. Assume that the radius of the copper atom is 127.8 pm, use the information given below to find out the density of copper metal. (M = 63.55 u and NA = 6.02 × 10223 mol-1) (All India 2012)(3 marks)
Ans: (a) Glass has a tendency to crystallise over long periods of time. Hence, over the years, since the glass objects are ancient, their properties such as appearance change to become milky.
(b) Number of atoms in the unit cell, Z = 4 Radius = 127.8
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