CBSE Class 10 Science Revision Notes Chapter 4

CBSE Class 10 Science Chapter 4 Revision Notes:

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CBSE Class 10 Science Chapter 4 – Carbon and Its Compounds Notes -(Add revision notes PDF)

Access Class 10 Science Chapter 4 – Carbon and its Compounds

Introduction:

The element carbon and its compounds play a significant role in various domains of our lives. It is present as a constituent in several substances of food in the form of starch, sugar, and fats, in fuels as a component of wood, coal, petrol, and household and commercial particulars such as cosmetics, oils, paints, textile fabrics like cotton, nylon, silk, drugs, and disinfectants such as aspirin, penicillin, perfumes, and explosives such as dynamite, TNT, picric acid, dyes of indigo, congo red and malachite green colourations and poisons such as opium and strychnine. 

Bonding in Carbon – The Covalent Bond:

Covalent bonds come into the picture when we talk about bonding in carbon. One can describe covalent bonds as “The force of attraction originating from mutual sharing of electrons between two atoms”. Within a covalent bond, one, two, or three electron pairs are shared between atoms. This sharing of electrons can happen between two similar or dissimilar atoms, which attain stability accordingly. During mutual electron sharing between the atoms, the combined state is such that each atom attains the nearest noble gas configuration. The covalent bond between two atoms is denoted by a (-) that connects them. The formation of covalent bonds leads to the formation of covalent compounds. 

Properties of Covalent Compounds:

Many different properties are associated with covalent bonds. They are as follows: 

• Covalent compounds have the property of existing as molecules and not ions. 
• Covalent compounds’ melting and boiling points are generally low and usually insoluble or exhibit low solubility in water and other polar solvents. 
• In the condition of average temperatures, covalent compounds exist as gases or liquids. However, a few chemicals such as sugar and urea exist in the form of solids. 
• A covalent bond can be formed in different ways. The bond created by sharing just one pair of electrons between the atoms is called a “single covalent bond” or a “single bond”. In the case of “multiple covalent bonds”, there is mutual sharing of more than one electron pair; examples of such bonds are double and triple covalent bonds. 
• Covalent compounds exhibit poor conduction of electricity when they are fused or dissolved.

Types of Covalent Bonds:

There are many types of covalent bonds such as single bonds, and double and triple covalent bonds. 

Single Bond

• A single covalent bond can be explained through hydrogen bonding. In the outermost shell of hydrogen, there is only one electron present. To attain the nearest noble gas configuration, which is helium, two atoms of hydrogen give one electron each for sharing of the pair. In this process, a single covalent bond is formed. 
• Such a bond formation can also be explained through a chlorine molecule that has seven valence electrons. Each of the two chlorine atoms requires one electron to achieve the nearest noble gas configuration; a pair of electrons are mutually shared between the atoms.

Double Bond

• The concept can be better explained by utilising the oxygen molecule in the case of double covalent bond formation. The number of valence electrons of oxygen is six; therefore, it requires two electrons to achieve the configuration of the nearest noble gas. Hence, there is a mutual sharing of two pairs of electrons between two oxygen atoms forming a double covalent bond. 

Triple Bond

• The triple covalent bond formation can be witnessed in nitrogen molecules. Nitrogen has five valence electrons and requires three additional electrons to obtain the nearest noble gas configuration. Hence, the two nitrogen atoms share three pairs of electrons, forming a triple covalent bond.

Multiple Bond 

• The combination of double or triple bonds leads to the formation of multiple bonds. 

Allotropes of Carbon:

• Allotropy is used to describe the occurrence of different existential forms of an element with different physical but same chemical properties. Such forms of an element are called allotropes or allotropic forms. 
• There are allotropes of carbon such as diamond and graphite in the crystalline form, coal, coke, charcoal, petroleum coke, lampblack, animal charcoal, or bone black in the amorphous form.
• Diamond and graphite are two allotropes of carbon in the crystalline form with vast differences in their qualities.

Comparison of Diamond and Graphite Properties:

Amorphous Forms of Carbon:

Coal:  

Coal is generated naturally through the ‘carbonisation’ of wood. The carbonisation process is converting wood to coal under the influence of the absence or lack of air, high temperature, and high pressure. Among the different coal types, anthracite is the purest form, with a carbon content of 94-95%. 

Wood Charcoal:

Wood charcoal is formed when the wood is burned rapidly in the presence of a little amount of air. The name of this technique is a destructive distillation of wood, and it is permissible for the volatile products to escape. Charcoal is porous in nature, brittle, and a black substance that works well as an adsorbent.

Animal Charcoal:

Animal charcoal, also known as bone charcoal, is formed by the distillation of bones. Amorphous carbon makes up roughly 10% to 12% of the total carbon content.

Sugar Charcoal:

Sugar charcoal is formed by the process of heating sugar in the absence of air and forming the purest amorphous carbon form. 

Lamp Black:

Lamp black, a silky black powder, is formed when tar and vegetable oils are burnt in the room with insufficient air, and the resulting soot is deposited on damp blankets.

Carbon Black:

Carbon black is formed when soot is deposited on the underside of a revolving disc at the time when natural gas is burnt in a limited air supply, which is scraped off and stored in bags. 

Gas Carbon and Petroleum Coke:

Gas carbon refers to the carbon substance scraped off the retort wall used for destructive coal distillation. Petroleum coke is a substance deposited on the walls of distillation towers during crude petroleum refining.

Fullerenes:

Another form of carbon allotropes is fullerenes, enormous spherical cage-like molecules discovered in 1985 in interstellar dust and geological formations. Examples: C32, C50, C60, C70, C76 and C84 are the most well-known fullerenes. The symmetry of C60 is exemplary, representing an aromatic system with 20 hexagons and 12 pentagons of carbon atoms that are fused together in a ring structure. The structure bends and shuts to form a molecule in the shape of a soccer ball. Another name for C60 is Buckyball.

Organic Compounds –

Carbon and hydrogen compounds.

Organic chemistry deals with the study of carbon and hydrogen compounds. 

Distinguishing Features of Organic Compounds:

The features of the organic compounds are as follows: 

• Covalent bonds are observed 
• Low melting and boiling points
• Solubility in organic solvents but not in the water
• Poor electrical conductivity 
• Complex and slow nature of organic reactions
• Low heat resistance 
• Flammable nature

The Creation of a Huge number of Organic Compounds has Several Causes:

There are several causes behind the creation of organic compounds, such as catenation which refers to the ability of atoms to bind, forming chains of identical atoms, formation of C-C multiple bonds due to the small size of carbon atoms, isomerism which refers to the formation of same molecules with different structural formulas and shapes. 

Saturated and Unsaturated Carbon Compounds:

• Saturated carbon compounds refer to those compounds that are carbon and hydrogen compounds with a single link between the neighbouring carbon atoms. There is complete utilisation of all four carbon bonds, and no more hydrogen atoms or other atoms may have the capacity to bind to it. This is why they undergo substitution reactions and are called saturated carbon compounds.
• Unsaturated compounds refer to the carbon and hydrogen compounds with the presence of one double covalent link between carbon atoms or triple covalent bond between carbon atoms. Unsaturated compounds have more hydrogen atoms than saturated compounds and go through additional reactions.

Properties of Saturated and Unsaturated Compounds:

Classification of Hydrocarbons:

Hydrocarbons are classified as open chain/ aliphatic/acyclic compounds and carbocyclic compounds. There are three aliphatic hydrocarbon types: alkenes, alkanes, and alkynes. There are two forms of carbocyclic compounds: alicyclic and aromatic. 

Affinity of Carbon with Other Elements:

Carbon has a strong capacity for forming a spectrum of carbon and hydrogen compounds. Such bonds are formed when one or more hydrogen atoms are substituted by an element, for example, nitrogen, sulphur, and so on, and a hydrocarbon chain is formed when the valency of carbon is sustained. One can understand the term “functional group” as an atom or group of atoms that form a bond with the carbon atom in the form of a chain or ring of an organic compound while exhibiting distinct features. 

Homologous Series & Nomenclature:

A homologous series refers to the collection of molecules with similar chemical structures. Molecules in such a series have similar chemical and structural features. The two consecutive members of a homologous series are separated by the CH2 group in their molecular formula. Each component follows a general molecular formula in a homologous series and has a comparable functional group. The difference between the molecular formula of each successive component of a homologous series is by one unit. 

The term nomenclature refers to “The system of designating a suitable name to a particular carbon compound based on certain rules”. Most of the carbon compounds have either the Trivial or the IUPAC names. 

Trivial Names:

Trivial names are the common names of chemical compounds derived from the compound’s source. However, the names of such compounds were repetitive and unclear.

IUPAC Names

IUPAC names derive from the rules of the system proposed by the International Union for Pure and Applied Chemistry (IUPAC) that constitutes naming the carbon compounds with valid scientific names. 

There are three main compounds in the scheme, which are the number of carbon atoms in a molecule referring to as Wood Root, for example, C1 – Meth, C2 – Eth, C3- Prop, C4- But, a suffix which refers to the bond type or the functional group that is present in the carbon chain such as “ol” for alcohols – (-OH), “ene” (double bond), “al” for aldehydes – (-CHO) and prefix that denotes the position of other functional groups, for example, the compound with Word root: But (C4), Prefix: 3, chloro, Suffix: -ol can be called as  3-chloro butanol. 

Isomers and Isomerism:

Isomers are compounds that constitute different structural but similar molecular formulas, and the process is isomerism. There are two types of isomerism which are chain and functional isomerism. Chain isomerism is a process wherein different carbon chain skeletons distinguish the isomers. Example: n-butane and iso-butane. Functional isomerism is where distinct functional groups are present that distinguish the structures of isomers. 

Chemical Properties of Carbon Compounds:

Combustion:

Combustion refers to the exothermic process of burning a substance that generates a lot of heat energy. The by-products of carbon burning are water, carbon dioxide, heat energy, and its compounds. 

The conditions needed for the combustion of fuel are three in number. The first condition is the presence of a substance that is combustible. Diamond is not flammable, while petroleum is. The following condition is the presence of a combustion promoter in the form of atmospheric air or oxygen gas, without which combustion is impossible. Nitrogen and carbon dioxide do not aid in combustion. The last condition necessary for combustion is sufficient heat for attaining the ignition temperature. 

Oxidation:

When carbon-containing compounds are burnt in oxygen or air, they undergo an oxidation process. Oxidation of carbon molecules produces other carbon compounds with different functional groups like alcohol, ethers, carboxylic acid etc. The oxidation process is accomplished by oxidising agents or an oxygen environment such as alkaline KMnO4 and acidified K2Cr2O7.

Addition Reaction:

Additional reactions refer to those where the unsaturated hydrocarbons react with another chemical to produce a single product. Double carbon bonded alkenes readily react with specific compounds to generate saturated addition products. The addition of a hydrogen molecule across the double bond of an alkene for the production of saturated substances is called hydrogenation. It takes place in the presence of catalysts such as nickel.

Unsaturated double-bonded compounds are found in vegetable oils like mustard, groundnut oil, and vegetable ghee, a saturated compound that results from hydrogenation at double bonds. In an alkane molecule, the hydrogen is replaced by another or group of atoms during substitution, which forms derivatives of that hydrocarbon. 

Substitution Reaction: 

It occurs when one or more atoms in a molecule are replaced or substituted by other atoms or a group of atoms. 

Example: 

Chlorination occurs when a combination of methane and chlorine is exposed to sunlight or heated to a temperature of 250-300 degrees celsius. A variety of substitution products are formed when there is an overabundance of chlorine, such as in the case of ethane, which creates many substitution products like methane when high chlorine and sunlight are present. 

Carbon Containing Compounds:

Alcohol is a term usually used for referring to ethanol, which man has utilised for ions, specifically in wine production. The molecular formula of ethanol is CH3CH2OH or  C2H5OH.

The characteristics of ethanol include colourless liquid with a boiling point of 78 degrees Celsius, a pleasant odour, a freezing temperature of -114degrees Celsius, solubility in water, all organic solvents, and high intoxicity in nature. Ethanol is flammable in nature and produces a blue flame when it is burnt. Hydrogen gas bubbles can be seen when ethyl alcohol is added with a small amount of salt.

Uses: 

• These are all essential chemical compounds that are employed in the chemical industry.
• Ethyl alcohol dissolves many organic solutes, especially insoluble in water.
• The chemical is used to make perfumes.
• This fuel is used to make gasoline, a blend of 90% gasoline (gasoline) and 10% ethanol. As a result, gasoline consumption is reduced.
• Ethyl alcohol is used to make tinctures and medical syrups.
• Alcoholic drinks contain it.
• Paints, varnishes, and dyes, among other things, can be dissolved in it.
• A variety of organic chemicals are made from it.

Chlorination of Methane:

Methane can be chlorinated by the combination of methane and chlorine under sunlight or at high temperatures. When there is excess chlorine a variety of substitution products are formed. 

Effect of Alcohol on Human Beings:

A collection of organic compounds with the -OH group is called alcohol in chemistry. However, when people use “alcohol,” they mean ethyl alcohol or ethanol. It can be used for various things, but notably as a solvent. However, alcoholic beverages, including wine, beer, rum, brandy, and whiskey, are the most widely used form of alcohol. In small doses, it can be utilised as a source of energy, but it can damage the neurological system in large quantities. The person loses mental and muscle control, as well as their sense of balance. This practice has the potential to develop into a habit. Long-term alcohol consumption can be detrimental to one’s health, especially the liver, which is prone to cirrhosis. This type of consumption can be lethal and can ruin a person’s family life.

Methylated Spirit or Denatured Alcohol:

A denatured spirit or methylated spirit combination is produced to deter excessive ethanol consumption.

Remember

To prevent the drinking problem in people, denatured alcohol or methylated spirit mixture is used. 

Spurious Alcohol:

This form of alcohol is illegal and produced by using methylated spirit or poor distillation techniques. The lower segments of our society primarily utilise it since it is affordable. It contains more hazardous methyl alcohol. Such alcoholic beverages may cause blindness, severe other health problems, and even death. Ethyl alcohol may occasionally be combined with other substances to give the consumer an “intoxicating” sensation. Even these are highly harmful to the body and have the potential to kill.

Ethanoic Acid:

One of the most common organic acids is acetic acid, which has been used for a very long period as vinegar. It can also be obtained from many fruit juices. It is in mixed form in various oils and essential oils.

 Formula – CH3COOH

Reactions of Alkyl Group – Halogenation:

The three hydrogen atoms get replaced with three halogen atoms of the alkyl group in acetic acid.

Reactions Involving Replaceable Hydrogen Atom:

Acetic acid ionises to form hydrogen ions in polar fluids, which give it its acidic characteristics.

As a result, metals, alkali metal carbonates, and alkalis react with acetic acid.

With Alkalis, Carbonates, and Bicarbonates:

Acetic acid neutralises alkalis, turning blue litmus into red, and produces salt and water when it reacts with alkalis. Effervescence is a sign that carbonates and bicarbonates are breaking down, releasing carbon dioxide. Use the bicarbonate test to determine if a substance has a carboxyl group.

With Metals:

When acetic acid interacts with strongly electropositive metals like sodium and zinc, it produces acetate and releases hydrogen.

With Alcohols:

Acetic acid reacts with alcohols to form esters when dehydrating substances like anhydrous zinc chloride or concentrated sulfuric acid are present.

Reactions Involving Carboxyl Group as a Whole:

Dry distillation of the anhydrous alkali salts of acetic acid with soda-lime results in methane production.

Reduction:

Acetic acid cannot be subjected to reduction, but it can be converted to ethane by heating it under pressure with a lot of hydriodic acids and red phosphorus. This can also be achieved by utilising a nickel catalyst and heating the acid with hydrogen at high temperatures and pressures.

In the presence of lithium aluminium hydride, acetic acid can be converted to ethanol. The same outcome is obtained by hydrogenating in the presence of ruthenium or copper-chromium oxide catalysts.

Oxidation:

Carbon dioxide and water are released when acetic acid is oxidised and heated for a long time with a potent oxidising agent.

Uses:

• Ethanoic acid is used in the production of dyes, fragrances, and rayon.
• Milk and latex are used to make casein and rubber. It helps the blood to coagulate.
• In the form of salts in both medication and paint.
• Acetates of aluminium and chromium are used as mordants.
• It is used as vinegar when diluted and as a solvent when concentrated.
• As organic esters that can be used as scents.

Soaps & Detergents:

Introduction:

Cleansing agents like soaps and detergents react with water to remove impurities from solid surfaces (e.g., cloth or skin). While synthetic detergents are manufactured from mineral oils, soaps are made from the oils and fats found in plants and animals (petroleum or coal hydrocarbon compounds). Chemically, higher fatty acids like stearic, palmitic, and oleic acids, either saturated or unsaturated, can be satisfied with sodium or potassium to form soaps. 

They contain a long hydrocarbon chain with a single carboxylic acid functional group. Unlike unsaturated fatty acids like oleic and linoleic, which have one or more double bonds in their molecules, saturated fatty acids, like stearic and palmitic, only contain single bonds in their molecules. 

As a result, the following acids’ sodium salts are frequently used to make soap:

• Stearic acid (C17H35COONa), a saturated fatty acid, is generated from vegetable oils, including linseed and soybean oil.
• Animal fat, palm oil, and sodium palmitate (C17H31COONa), a form of saturated fatty acid, palmitic acid.
• Oleic acid, an unsaturated fatty acid, is present in vegetable oils, including linseed oil and soybean oil, in the form of sodium oleate (C17H33COONa).

Difference Between Toilet Soap and Laundry Soap:

Hard soap is produced when soap is made from the sodium salts of the acids of cheap oils or fats. These soaps, including free alkalis, are typically used as washing bars for clothes. High-quality oils and fats are combined with their potassium salts to create soft soap. These soaps contain no free alkalis. Because they produce more lather, they are used as shaving creams, shampoos, and toilet soaps.

Cleansing Action Of Soap:

A soap molecule is made with oppositely polarised ends, just like a tadpole. The long hydrocarbon chain at one end is hydrophobic and nonpolar. Hence it is soluble in oil but insoluble in water. On the other hand, the short polar carboxylate ion is hydrophilic, which is soluble in water but insoluble in oil and grease.

A colloidal soap solution is created when soap is stirred after being combined with water. By concentrating the fluid on the surface during agitation, foaming is produced. This helps the soap molecules penetrate the fabric and produce a unimolecular layer on the water’s surface. A soap molecule’s hydrophobic extended non-polar end is drawn to and surrounds dirt (fat or oil with dust absorbed). The mechanical rubbing or tumbling action is then used to remove the dirt and grease from the fabric. These are displaced by the extra water and washed away, leaving the fabric clean.

Limitations of Soaps:

In hard water, soaps don’t wash as well and don’t lather or froth as they should. The calcium, magnesium, or iron ions in hard water produce scum, an intractable sticky precipitate with a greyish appearance that reduces the cleaning power of soap and makes washing more challenging. Additionally, the scum hardens and fades the fabric as it forms. As a result, cleaning is useless, and a lot of soap is wasted.

Synthetic Detergents:

Detergent is a non-soapy cleaning agent that removes dirt from solutions by applying a surface-active component. Synthetic detergents are referred to as soapless soaps. Unlike soaps, they do not form scum. Therefore, they are still effective in hard or salt water. The alkyl or aryl sulfonates are modern synthetic detergents from coal, oil, petroleum, and sulfuric acid. They are described as “the sodium or potassium salt of a long chain alkyl benzene sulphonic acid that has washing characteristics in water, or “the sodium or potassium salt of a long chain alkyl hydrogen sulphate that has cleansing characteristics in water.” 

Cleansing Action of Detergents:

Synthetic detergents share the same molecular structure as soaps, which is a tadpole-shaped molecule with two components at each end: an extended, non-polar hydrocarbon group that is hydrophobic (repels water) and a short, ionic group that is hydrophilic (attracts water) (hydrophilic). Because of this, the cleansing process is the same as soaps, which entails the formation of micelles and then emulsification.

Advantages of Detergents:

• Synthetic detergents clean well and lather even in hard water and salt water (sea water).
• Detergents do not degrade in an acidic environment since they are the salts of potent acids. Detergents can, therefore, effectively clean the fabric even in acidic water.
• Synthetic detergents have a stronger cleaning action than soaps and are more water-soluble. Detergents utilise less natural vegetable oil, a crucial cooking medium because they are produced from petroleum.

Disadvantages of Detergents:

• Surface-active substances like detergents are a significant cause of a wide range of water pollution problems.
• Because they are resistant to biological agents, many detergents are not biodegradable. Using conventional treatment techniques, it is challenging to get rid of them from municipal wastewater.
• They often create stable foams in rivers that extend hundreds of metres into the water. This is true because of the effect the surfactants employed in their production have on the environment. As a result, they put aquatic life in peril.
• They reduce oxidation in wastewater because they create an envelope-like structure around organic molecules.

Differences between Soaps and Detergents

Carbon and its Compounds Class 10 Notes – Free PDF Download

Class 10th Science Chapter 4 Notes

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