[TERM 2] Carbon and its Compounds Class 10 Notes, Important Points and Explanation

Carbon And Its Compounds Class 10 Notes

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Carbon and its Compounds Class 10 notes, Main Points and Explanation

Carbon and its Compounds class 10 pdf

Properties of Carbon 

  • The element carbon is non-metal. Its symbol is C. 
  • Carbon is a versatile element. The percentage of carbon present in earth’s crust in form of mineral is 0.02% and in atmosphere as CO2 is 0.03%. 
  • All the living things, like plants and animals are made up of carbon based compounds.  Carbon always forms covalent bonds. 
  • The atomic number of carbon is 6.

Ionic Bond in Class 10 science chapter 4 notes

Ionic bonding involves the transfer of valence electron/s, primarily betweena metal and a non metal. The electrostatic attractions between theoppositely charged ions hold the compound together.

Ionic compounds:

  • Are usually crystalline solids (made of ions)
  • Have high melting and boiling points
  • Conduct electricity when melted
  • Are mostly soluble in water and polar solvents

Covalent Bond in Class 10 science chapter 4 notes

A covalent bond is formed when pairs of electrons are shared between two atoms. It is primarily formed between two same nonmetallic atoms or between nonmetallic atoms with similar electronegativity.
 

Conditions for formation of a covalent bond:

  • The combining atoms should have 4 to 7 electrons in their valence shell.
  • The combining atoms should not lose electrons easily.
  • The combining atoms should not gain electrons readily.
  • The difference in electronegativity of two bonded atoms should be low.

Properties of covalent compounds:

  • Physical state: They are generally liquids or gases. Some covalent compounds may exist as solid.
  • Solubility: They are generally insoluble in water and other polar solvents but soluble in organic solvents such as benzene, toluene etc.
  • Melting and boiling points: They generally have low melting and boiling points.
  • Electrical conductivity: Covalent compounds are generally poor conductor of electricity. This is because the electrons are shared between atoms and no charged particles are formed in these compounds.

Types of Formula for Writing Hydrocarbons:

  • Molecular formula: It involves the actual number of each type of atom present in the compound.
  • Structural formula: The actual arrangement of atoms is written in structural formula.
  • Condensed formula: It is the shortened form of the structural formula.
These heteroatoms or group of atoms which make carbon compound reactive and decides its properties are called functional groups.
 
Homologous Series: A series of organic compounds in which every succeeding member differs from the previous one by – CH2 or 14 a.m.u. is called homologous series.
The molecular formula of all the members of a homologous series can be derived from a general formula.
  • Properties of a homologous series: As the molecular mass increases in a series, physical properties of the compounds show a variation, but chemical properties which are determined by a functional group remain the same within a series.
  • Homologous series of alkanes: General formula: CnH2n+ 2, where n = number of carbon atoms. CH4, C2H6, C3H8.
  • Homologous series of alkenes: General formula: CnH2n, where n = number of carbon atoms. C2H4, C3H6, C4H8.
  • Homologous series of alkynes: General formula: CnH2n–2, where n = number of carbon atoms. C2H2, C3H4, C4H6.

Class 10 Term 2 Xam Idea Books Class 10

Tetravalency:

Having a valency of 4, carbon atom is capable of bonding with atoms of oxygen, hydrogen, nitrogen, sulphur, chlorine and other elements. The smaller size of carbon atom enables nucles nucleus to hold the shared pair of electrons strongly, thus carbon compounds are very stable in general.
 

Saturated and Unsaturated Carbon Compounds:

Formulae and Structures of Saturated Compounds of Carbon and Hydrogen:

Nomenclature of Carbon Compounds:

1. Identify the number of carbon atoms in the compound.

2. Functional group is indicated either by prefix or suffix
 
3. If a suffix is added, then final ‘e’ is removed from the name eg. methanol (methane-e = methan + ol)
.

.

 

Lewis Dot Structure:

Lewis structures are also known as Lewis dot structures or electron dot structures. These are basically diagrams with the element’s symbol in the centre. The dots around it represent the valence electrons of the
element.
 

Covalent Bonding in H2, N2 and O2

Formation of a single bond in a hydrogen molecule:

Each hydrogen atom has a single electron in the valence shell. It requires one more to acquire nearest noble gas configuration (He).Therefore, both the atoms share one electron each and form a single bond.

Formation of a double bond in an oxygen molecule:

Each oxygen atom has six electrons in the valence shell (2, 6). Itrequires two electrons to acquire nearest noble gas configuration (Ne).Therefore, both the atoms share two electrons each and form a double bond.
 

Formation of a triple bond in a nitrogen molecule:

Each nitrogen atom has five electrons in the valence shell (2, 5). It requires three electrons to acquire nearest noble gas configuration (Ne).Therefore, both atoms share three electrons each and form a triple bond.

Single, Double and Triple Bonds and Their Strengths:

A single bond is formed between two atoms when two electrons are shared between them, i.e., one electron from each participating atom. It is depicted by a single line between the two atoms.
 
A double bond is formed between two atoms when four electrons are shared between them, i.e., one pair of electrons from each participating atom. It is depicted by double lines between the two atoms.
 
A triple bond is formed between two atoms when six electrons are shared between them, i.e., two pairs of electrons from each participating atom. It is depicted by triple lines between the two atoms.
 

Bond Strength in Class 10 science chapter 4 notes

  • The bond strength of a bond is determined by the amount of energy
  • required to break a bond.
  • The order of bond strengths when it comes to multiple bonds is:
  • Triple bond>double bond>single bond
  • This is to signify that the energy required to break three bonds is higher
  • than that for two bonds or a single bond

Bond length in Carbon and its Compounds Class 10 Notes

  • Bond length is determined by the distance between nuclei of the two atoms in a bond.
  • The order of bond length for multiple bonds is: Triple bond<doublebond<single bond The distance between the nuclei of two atoms isleast when they are triple bonded.

Covalent Bonding of N, O with H and Polarity

In ammonia (NH3), the three hydrogen atoms share one electron each with the nitrogen atom and form three covalent bonds.
  • Ammonia has one lone pair.
  • All the three N-H covalent bonds are polar in nature.
  • N atom is more electronegative than the H atom. Thus the shared pair of electrons lies more towards N atom.
  • This causes the N atom to acquire a slight negative charge, and H atom a slight positive charge.
In water (H2O), the two hydrogen atoms share one electron each with the oxygen atom and form two covalent bonds.
  • Water has two lone pairs.
  • The two O-H covalent bonds are polar in nature.
  • O atom is more electronegative than the H atom. Thus the shared pair of electrons lies more towards O atom.
  • This causes the O atom to acquire a slight negative charge, and H atom a slight positive charge.
Covalent Bonding in Carbon
A methane molecule (CH4) is formed when four electrons of carbon are shared with four hydrogen atoms as shown below.

Mp,Bp and Electrical Conductivity:

Covalent compounds Carbon and its Compounds Class 10 Notes

  • Are molecularcompounds
  • Are gases, liquids or solids
  • Have weak intermolecular forces
  • Have low melting and boiling points
  • Are poor electrical conductors in all phases
  • Are mostly soluble in nonpolar liquids

Esterification :

Carboxylic acids react with alcohols in presence of few drops of concentrated sulphuric acid as catalyst and form sweet smelling compounds called ester.

Hydrolysis in Carbon and its Compounds Class 10 Notes

 On heating with an acid or a base the ester forms back the original alcohol and carboxylic acid.

 

*Alkaline hydrolysis of ester is also called saponification.

Soaps and Detergents:

  • Soap is sodium and potassium salt of carboxylic acids with long chain.
  • Soaps are effective with soft water only and ineffective with hard water.
  • Detergents are ammonium or sulphonate salts of carboxylic acids with long chain. They are effective with both soft as well as hard water.

 An ionic part (hydrophilic) and a long hydrocarbon chain (hydrophobic) part constitutes the soap molecule.

Cleansing Action of Soaps :

Most dirt is oily in nature and the hydrophobic end attaches itself with dirt, while the ionic end is surrounded with molecules of water. This result in formation of a radial structure called micelles

Allotropes of Carbon:

  • The phenomenon of existence of the same element in different physical forms with similar chemical properties is known as allotropy.
  • Some elements like carbon, sulphur, phosphorus, etc., exhibit this phenomenon.
  • Crystalline allotropes of carbon include diamond, graphite and, fullerene.
  • Amorphous allotropes of carbon include coal, coke, charcoal, lamp black and gas carbon.

Diamond:

Diamond has a regular tetrahedral geometry. This is because each carbon is connected to four neighbouring carbon atoms via single covalent bonds, resulting in a single unit of a crystal. These crystal units lie in different planes and are connected to each other, resulting in a rigid three-dimensional cubic pattern of the diamond.

Diamond:

  • Has a high density of 3.5g/cc.
  • Has a very high refractive index of 2.5.
  • Is a good conductor of heat.
  • Is a poor conductor of electricity.

Graphite

In graphite, each carbon atom is bonded covalently to three other carbon atoms, leaving each carbon atom with one free valency. This arrangement results in hexagonal rings in a single plane and such rings are stacked over each other through weak Van der Waals forces.

Graphite:

  • Has a density of 2.25 g/cc.
  • Has a soft and slippery feel.
  • Is a good conductor of electricity.

Oxidation in Carbon and its Compounds Class 10 Notes

By use of mild oxidizing agent, CrO3 (chromic anhydride), ethanol CH3CH2OH is oxidised to ethanal (CH3CHO).
Whereas, by use of a strong oxidizing agent like (alkaline KMnO4 or acidified K2Cr2O7), ethanol CH3CH2OH is oxidised to ethanoic acid (CH3COOH).
 
 

Addition:

The reactions in which two molecules react to form a single product having all the atoms of the combining molecules are called addition reactions.
The hydrogenation reaction is an example of the addition reaction. In this reaction, hydrogen is added to a double bond or a triple bond in the presence of a catalyst like nickel, palladium or platinum.

Substitution:

The reaction in which an atom or group of atoms in a molecule is replaced or substituted by different atoms or group of atoms is called substitution reaction. In alkanes, hydrogen atoms are replaced by other elements.

Hard Water:

Hard water contains salts of calcium and magnesium, principally as bicarbonates, chlorides, and sulphates. When soap is added to hard water, calcium and magnesium ions of hard water react with soap forming insoluble curdy white precipitates of calcium and magnesium salts of fatty acids.
 
2C17H35COONa +MgCl2 → (C17H35COO)2Mg + 2NaCl
2C17H35COONa + CaCl2 → (C17H35COO)2Ca + 2NaCl
 
These precipitates stick to the fabric being washed and hence, interfere with
the cleaning ability of the soap. Therefore, a lot of soap is wasted if water is hard.
  • Catenation: The self linking property of carbon atoms through covalent bonds to form long chains and rings is called catenation.
  • Tetravalency: Tetravalency is the state of an atom in which there are four electrons available with the atom for covalent chemical bonding.
  • Electronegativity: It is the ability of an atom to attract a shared pairs of electrons towards itself.
  • Isomerism: The compounds which possess the same molecular formula but different structural formulae, are called isomers, and the phenomenon is known as isomerism. For example, butane with a molecular formula C4H10 has two isomer

Main Points of carbon and its compounds class 10 notes

  • Organogens : The elements from which organic life starts are called organogens. Carbon is the
    backbone of organic life, supported by elements hydrogen, nitrogen and oxygen.
  • States of carbon :
    (i) Carbon occurs in the free state as diamond, graphite and coal.
    (ii) Carbon occurs in the combined state as carbonates of metals, all kinds of living being, as
    petroleum and as carbon dioxide.
  • Covalent bond or Molecular bond or Homopolar bond : A chemical bond formed between two
    non-metallic elements by the mutual sharing of one or more electron pairs is called a covalent
    bond.
  • Single covalent bond : A chemical bond formed between two non-metallic elements by the mutual
    sharing of one electron pair only, is called a single covalent bond.
  • Double covalent bond : A chemical bond formed between two non-metallic elements by the mutual
    sharing of two electron pairs, is called a double covalent bond.
  • Triple covalent bond : A chemical bond formed between two non-metallic elements by the mutual sharing of three electron pairs, is called a triple covalent bond.
  • Covalency : The number of electron pairs which an atom of an element mutually shares with
    another atom or atoms of the same or different elements, so as to acquire a stable configuration
    like noble gases, is called covalency.
  • Covalent compound or Molecular compound : The chemical compound formed as a result
    of mutual sharing of electron pairs of two or more different kinds of atoms is called a covalent
    compound.
  • Non-polar covalent compound : A covalent compound in which the shared pair of electrons are
    equally distributed between two or more different atoms is called a non-polar covalent compound.
    For example, methane, ethane, etc.
  • Polar covalent compound : A covalent compound in which the shared pair of electrons are
    unequally distributed between the two atoms, is called a polar covalent compound. For example,
    water, hydrochloric acid, etc.
  • Properties of covalent (molecular) compounds :
    (i) They have low melting points and boiling points.
    (ii) They have low densities, i.e., their density is generally less than that of water.
    (iii) They are generally gaseous or volatile liquids or soft solids.
    (iv) They are insoluble in water, but soluble in organic solvents.
    (v) They are bad conductors of electricity.
  • Diamond is the purest crystalline form of carbon which is the hardest naturally occurring substance.
    Other pure crystalline forms of carbon are graphite and fullerenes. In Buckminsterfullerene, each
    molecule has 60 atoms arranged in hexagons and pentagons.
  • Catenation : The property of carbon atoms to link with other carbon atoms or the atoms of other
    elements with single, double or triple covalent bonds, so as to form large number of compounds
    is called catenation.
  • Organic chemistry : The branch of chemistry dealing with carbon compounds other than carbon
    monoxide, carbon dioxide and carbonates is called organic chemistry.
  • Organic compounds : The compounds of carbon, other than CO, CO2 and carbonates, hydrogen
    carbonates are called organic compounds.
  • Saturated organic compounds : Organic compounds in which all the four valencies of carbon
    atoms are satisfied by single covalent bonds, are called saturated organic compounds.
  • Unsaturated organic compounds : Organic compounds in which a double or a triple bond exists
    between two carbon atoms in a carbon chain, are called unsaturated organic compounds.
  • Hydrocarbons : Organic compounds which contain only carbon and hydrogen atoms are called
    hydrocarbons.
  • Straight chain hydrocarbons : Hydrocarbons, in which all the carbon atoms are linked to one
    another in a straight chain by single covalent bonds are called straight chain hydrocarbons.
    Branched chain
  • hydrocarbons : Hydrocarbons, in which one or more carbon atoms are attached to the main straight chain of carbon atoms by a single covalent bond are called branched chain
    hydrocarbons.
  • Straight chain hydrocarbons : Hydrocarbons, in which all the carbon atoms are linked to one
    another in a straight chain by single covalent bonds are called straight chain hydrocarbons.
  • Branched chain hydrocarbons : Hydrocarbons, in which one or more carbon atoms are attached
    to the main straight chain of carbon atoms by a single covalent bond are called branched chain
    hydrocarbons.
  • Isomerism : The phenomenon due to which there can exist two or more organic compounds, with
    different physical and chemical properties, due to the difference in the arrangement of carbon atoms in their structure, but have the same chemical formula is called isomerism.
  • Isomers : Organic compounds having the same molecular formula but different structural formulae,
    and hence, different physical and chemical properties, are called isomers.
  • Straight chain unsaturated hydrocarbons : Hydrocarbons, in which carbon atoms are arranged
    in a straight chain, such that there is a double or triple covalent bond between a pair of carbon
    atoms are called straight chain unsaturated hydrocarbons.
  • Ring chain saturated hydrocarbons : Hydrocarbons, in which carbon atoms are arranged in the
    form of a ring and bonded by single covalent bonds are called ring chain saturated hydrocarbons.
  • Ring chain unsaturated hydrocarbons : Hydrocarbons, in which carbon atoms are arranged in
    the form of a ring and are bonded by one or more double covalent bonds are called ring chain
    unsaturated hydrocarbons.
  • Alkanes [saturated hydrocarbons] : Compounds of carbon and hydrogen, in which all the
    valencies of carbon atoms are satisfied by single covalent bonds are called saturated hydrocarbons
    or alkanes.
    General formula of alkanes is CnH2n + 2 where ‘n’ stands for the number of carbon atoms.
  • Homologous series : A group of members of the same class of organic compounds, which differ
    from each other by a – CH2 group, when arranged in the order of ascending molecular mass, is
    called a homologous series.
  • Homologues : The members of the same class of organic compounds, when arranged in the
    order of ascending molecular mass, such that they differ by 14 amu or a – CH2 group are called
    homologues
  • Alkenes : A homologous series of unsaturated hydrocarbons, characterised by the presence of double covalent bond (— C = C —) in the straight chain of carbon atoms, are called alkenes.
    General formula of alkenes is CnH2n , where n stands for the number of carbon atoms in the carbon
    chain.
  • Alkynes : A homologous series of unsaturated hydrocarbons, characterised by the presence of triple
    covalent bond (— C ≡ C —) in the straight chain of carbon atoms are called alkynes.
    General formula of alkynes is CnH2n – 2, where ‘n’ stands for the number of carbon atoms in the
    carbon chain.
  • Alkyl Radical : The fragment of an alkane molecule, from which one atom of hydrogen is removed
    from its straight chain is called an alkyl radical or alkyl group.
    General formula of alkyl group is CnH2n + 1 , where ‘n’ stands for number of carbon atoms in the
    carbon chain.
  • Functional group in an organic compound is an atom or group of atoms bonded together in such
    a unique fashion, that it is usually the site of chemical reactivity of an organic compound.
  • Alcohols are carbon compounds containing a — OH group attached to the carbon atom of an alkyl
    chain. IUPAC name for alcohols is alkanols and their general formula is CnH2n + 1 OH.
  • Aldehydes are carbon compounds containing a — CHO group attached to the carbon atom of an
    alkyl chain. IUPAC name for aldehydes is alkanals and their general formula is CnH2n + 1 CHO.
  • Ketones are the compounds containing C=O group, in which the carbon atom of C=O is
    attached to two carbon atoms of the same or different alkyl radicals.
  • Carboxylic acids are the compounds of carbon containing a — COOH group attached to the carbon
    atom of an alkyl chain.
    IUPAC name of carboxylic acids is alkanoic acids and general formula is R—COOH where R
    stands for alkyl radical having the general formula CnH2n + 1.
  • Halo alkanes : Halogen compounds of alkanes, obtained by replacing a hydrogen atom of an alkane
    with an atom of a halogen are called halo alkanes.
    General formula of halo alkanes is R—X where ‘R’ stands for an alkyl radical and ‘X’ stands for
    a halogen atom.
  • All allotropic forms of carbon as well as organic compounds burn in air/oxygen to form carbon
    dioxide and water (in the form of steam), with the release of a large amount of energy
  • The process of rapid burning of carbon or its compounds in air/oxygen, with the release of a lot
    of energy and formation of carbon dioxide and water is called combustion.
  • The region of burning gases when a substance burnt is called flame.
  • Some metallic salts impart colour to the non-luminous flame.
  • Coal and petroleum were formed when organic matter (plants and animals) got buried deep inside
    the earth and then decomposed by anaerobic bacteria.
  • When organic compounds are slowly oxidised by using oxidising agents other than atmospheric
    oxygen, the compounds form new organic products. Acidified potassium dichromate or alkaline
    potassium permanganate are strong oxidising agents.
    Copper (II) oxide, chromium oxide in acetic acid are mild oxidising agents
  • A reaction which proceeds with the breaking of double or triple covalent bonds in organic compounds so as to form new organic compounds having single covalent bonds, is called an addition reaction.
  • The conversion of unsaturated vegetable oils into saturated vegetable oil by the absorption of
    hydrogen in the presence of finely divided nickel is called hydrogenation of oils.
  • A chemical reaction in which hydrogen atoms in a saturated hydrocarbon are replaced by the atoms
    of some other elements is called a substitution reaction.
  • Ethanol (i) is a colourless and inflammable liquid, (ii) is miscible in water in all proportions,
    (iii) has a boiling point of 78.2°C and freezing point of – 118°C and (iv) is a bad conductor of
    electricity.
  • Ethanol reacts with sodium and potassium to form their respective ethoxides and hydrogen gas.
  • Ethanol gets dehydrated to ethene when heated with conc. sulphuric acid at 443 K (170°C).
  • All kinds of alcoholic drinks contain ethanol.
  • A mixture of 20% petrol and 80% alcohol is called power alcohol. It is used in automobiles.
  • Ethanol is used as an antifreeze in the radiators of motorcars in cold countries.
  • Excessive drinking of alcohol is bad for health as it slowly damages the liver and kidneys.
  • Methylated spirit is ethanol in which methanol is mixed. This makes it unfit for drinking purposes,
    but is extensively used in paints and varnish industry.
  • Pure ethanoic acid is a colourless corrosive liquid having a strong smell like that of vinegar.
  • A chemical reaction between ethanoic acid and any alcohol to form an acetate of the alcohol
    (commonly called ester), which is a sweet smelling product, is called esterification.

Last Lines of Class 10 science chapter 4 notes

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