notes of chapter 4 carbon and compounds in science class 10
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Answers
1. Bonding in Carbon
Carbon form covalent bonds.
Formation of covalent bond : Covalent bond formation involves sharing of electrons between bonding atoms which may be either same or different.
Covalency : The number of electrons contributed by an atom for sharing is known as its covalency
(i) These compounds are molecular in nature (i.e. they exist as single molecules)
(ii) These are insoluble in water and soluble in benzene, kerosene and petrol etc.
(iii) These compounds are poor conductor of electricity.
2. Allotropy in Carbon
The property due to which an element exists in two or more forms, which differ in their physical and some ofthe chemical properties is known as “Allotropy” and the various forms are called “Allotropes”.
Carbon exists in two allotropic form (i) crystalline (ii) amorphous. The crystalline forms are diamond and graphite whereas the amorphous forms are coal, charcoal, lamp black etc.
Fullerenes form another class of carbon allotropes. The first one to be identified was C-60, which has carbon atoms arranged in the shape of a football.
3. Unique Nature of Carbon
Catenation : The property of elements to form long chains or rings by self linking of their own atoms- through covalent bonds is called catenation. The extent of catenation depends upon the strength of the bonds between the atoms involved in catenation.
4. Saturated and Unsaturated Carbon Compounds
In saturated compounds the valencies of all the carbon atoms are satisfied by single bonds between them.
While in the unsaturated compounds, the valencies of all the carbon atoms are not satisfied by single bonds, thus in order to satisfy their valencies, they form double or triple bond between the carbon atoms.
5. Straight chain compounds : The compounds which contain straight chain of carbon atoms e.g. normal butane (C4H10), normal pentane (5H12) etc.
6. Branched chain compounds : Those compounds which are branched.
e.g. iso-butane (C4H10), isopentane (C5H12), neopentane (C5H12) etc.
7. Closed chain compounds or Ring compounds :
Cyclic compounds are called closed chain or ring compounds e.g. cyclohexane (C6H12), cyclopentane (C5H10), cyclobutane (C4H8), cyclopropane (C3H6) etc.
8. Hydrocarbons
All those compounds which contain just carbon and hydrogen are called hydrocarbons.
9. Functional Group
The atom or group of atoms which determine the properties of a compound is known as functional group. e.g. —OH (alcohol), —CHO (aldehyde), > C = C < (alkene), — C C — (alkyne) etc.
10. Homologous Series
A series of compounds in which the same functional group substitutes hydrogen in a carbon chain is called a homologous series.
e.g. CH3C1 and C2H5C1 differ by a —CH2 unit.
11. Nomenclature
Chemists developed a set of rules, for naming organic compounds based on their structures which is known as IUPAC rules.
The IUPAC name of an organic compounds consists of three parts.
Prefix – word root – Suffix
Word Root : A word root indicates the nature of basic carbon skeleton.
12. Chemical Properties of Carbon Compounds :
(i) Combustion : Carbon compound undergo combustion reaction to produce CO2 and H20 with the evolution of heat and light.
CH4 +O2 > CO2 + 2O + heat and light
(ii) Oxidation :
The substance which are used for oxidation are known as oxidising agent.
e.g alkaline KMnO4, acidified K2Cr2O7.
(iii) Addition reaction :
Unsaturated hydrocarbons (alkenes and alkynes undergo addition reaction in presence of catalysts e.g.
Science Class 10 Notes - Carbon and its Compounds
(iv) Substitution reaction : Saturated hydrocarbons give substitution reaction e.g. methane in presence of sunlight undergo chlorination.
13. Some Important Carbon Compounds
Alcohols : Compounds containing -OH group attached to a carbon atom are known as alcohols.
Example : Ethanol (C2H5OH) : commonly known as alcohol.
Properties of ethanol :
1. Reaction with sodium : Due to its weakly acidic nature, ethanol reacts with sodium to librate H2 gas.
Science Class 10 Notes - Carbon and its Compounds
2. Reaction with conc : H2SO4 :
Science Class 10 Notes - Carbon and its Compounds
Alcohol as a fuel : Alcohol (ethanol) is added to petrol upto 20% and the mixture is called “gasol”.
Harmful Effects of Drinking Alcohol :
If the alcohol used for drinking purposes contains some methyl alcohol (CH3OH) as impurity then it may cause serious poisoning and loss of eye sight.
It is habit forming and damages liver if taken regularly in large quantities.
Ethanoic Acid (Acetic Acid) CH3COOH:
Ethanoic acid, commercially known as acetic acid belongs to a group of acids called carboxylic acid.
Chemical properties :
(i) Reaction with a base :
2CH3COOH + 2NaOH → 2CH3COONaH2O
(ii) Reaction with carbonates and bicarbonates :
2CH3COOH + Na2CO3 → 2CH3COONa + CO2 + H2O
CH3COOH + NaHCO3 → CH3COONa + H2O + CO2
(iii) Reaction with alcohol : (Esterification)
Science Class 10 Notes - Carbon and its Compounds
Esters react is the presence of an acid or a. base to give back the alcohol and carboxylic acid-this reaction is known as saponification.
Answer:
soap and detergents
when soap is added to water , the soap molecules uniquely orient themselves to form spherical shape Michelle's.
The non polar hydrophobic part of tail of the soap molecules attracts the dirt or the oil part of the fabric , while the polar hydrophobic part or head,
( - COO _ NA+ ) , remains attracted to water molecules .
The agitation or scrubbing of the fabric helps the micelles to carry the oil or dirt particles and detach them from the fabric of the fabric.
HARD WATER
hard water contains salt of calcium and magnesium , principally as bicarbonates , chlorides and sulphates , when soap is added to water , calcium and magnesium ions of hard water react with soap forming insoluble curdy white precipitates of calcium and magnesium salts of fatty acids.
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 the water is hard.
COVALENT BONDS
To achieve the electronic configuration of the nearest noble as if the carbon atom loses our of its valence electrons a huge amount of energy is involved C4± ion hence formed will be highly enstable due to the presence of six protons and two electrons .
IONIC BOND
ionic bond involves the transfer of valence electrons primarily between a metal and a non metals . The electrostatic attractions between the oppositely charged ions hold the compound together.
ionic compounds
are usually crystalline solids ( made of iron )
have high melting and boiling points
conduct electricity when melted
are mostly soluble in water and polar solvents
LEWIS DOT STRUCTURE
Lewis structures are also known as Lewis dot structure or electron dot structure
Lewis structures of elements with atomic numbers 5-8
COVALENT BONDING IN CARBON
A methane molecules ( CH4 ) is formed when four electrons of carbon are shared with four hydrogen atoms.
ALLOTROPHS OF CARBON
The phenomenon of the existence of the same element is different physical forms with similar chemical properties is known as allotrophy.
some elements like carbon , sulphur , phosphorous etc exhibit this phenomenon .
crystalline allotrophs of carbon include diamond , graphite and fullerene.
Amorphous allotrophs of carbon include coal, coke, charcoal , lamp, black and gas carbon .
Hope it helps you