Periodic Classification of Elements, class 10th

Periodic Classification of Elements for Class 10th

Science Class 10 Notes for Periodic Classification of Elements

1. Classification means identifying similar species and grouping them together.

2. Lavoisier divided elements into two main types known as metals and non-metals.

3. Doberiner’s Law of Triads:

According to this law, “in certain triads (grout) of three elements) the atomic mass of the central element was the arithmetic mean of the atomic masses of the other two elements.” But in some triads all the threc elements possessed nearly the same atomic masses, therefore the law was rejected.

e.g., atomic masses of Li, Na and K are respectively 7, 23 and 39, thus the mean of atomic masses of I St and 3rd element is

Limitations of Doberiner’s Triads: He could identify only a few such triads and so the law could not gain importance. In the triad ofFe, Co, Ni, all the three elements have a nearly equal atomic mass and thus does not follow the above law

4. Newland’s Law of Octaves:

According to this law “the elements are arranged in such a way that the eighth element starting from a given one has properties which are a repetition of those of the first if arranged in order of increasing atomic weight like the. eight note of musical scale.”

Drawback of Newland’s law of Octaves:

(i) According to Newland only 56 elements exists in nature and no more elements would be discovered in the future. But later on several new element were discovered

whose properties did not fit into law of octaves.

(ii) In order to fit new elements into his table Newland adjust two elements in the same column, but put some unlike elements under the same column.

Thus, Newland’s classification was not accepted.

Mendeleev’s Periodic Table :

Mendeleev arranged 63 elements known at that time in the periodic table. According to Mendeleev “the properties of the elements are a periodic function of their atomic masses.” The table consists of eight vertical column called ‘groups’ and horizontal rows called ‘periods’.

Merits of Mendeleev’s Periodic Table:

(i) At some places the order of atomic weight was changed in order to justify the chemical and physical nature.

(ii) Mendeleev left some gap for new elements which were not discovered at that time.

(iii) One of the strengths of Mendeleev’s periodic table was that, when inert gases were discovered they could be placed in a new group without disturbing the existing

order.

Characteristics of the periodic table : Its main characteristics are :

(i) In the periodic table, the elements are arranged in vertical rows called groups and horizontal rows called periods.

(ii) There are eight groups indicated by Roman Numerals I, II, III, IV, V, VI, VII, VIII. The elements belonging to first seven groups have been divided into sub-groups designated as A and B on the basis of similarities. The elements that are present on the left hand side in each group constitute sub-group A while those on the right hand side form sub-group B. Group VIII consists of nine elements arranged in three triads.

(iii) There are six periods (numbered 1, 2, 3, 4, 5 and 6). In order to accomodate more elements, the periods 4, 5, 6 are divided into two halves. The first half ofthe elements are placed in the upper left corners and the second half occupy lower right corners in each box.

Achievements of mendeleev’s periodic table

(i) The arrangement of elements in groups and periods made the study of elements quite systematic in the sense that if properties of one element in a particular group are known, those of the others can be easily predicted.

(ii) Prediction of new elements and their properties : Many gaps were left in this table for undiscovered elements. However, properties of these elements could be predicted in advance from their expected position. This helped in the discovery of these elements. The elements silicon, gallium and germanium were discovered in this manner.

(iii) Correction of doubtful atomic masses :

Mendeleev corrected the atomic masses of certain elements with the help of their expected positions and properties.

Limitations of mendeleev’s classification :

(i) He could not assign a correct position of hydrogen in his periodic table, as the properties of hydrogen resembles both with alkali metals as well as with halogens.

(ii) The isotopes of the same element will be given different position if atomic number is taken as basis, which will disturb the symmetry of the periodic table.

(iii) The atomic masses do not increases in a regular manner in going from one elements to the next.

So it was not possible to predict how many elements could be discovered between two elements.

6. Modern Periodic Law : This law was given by Henry Moseley in 1913. it states, “Properties of the elements are the periodic function of their atomic numbers”.

Cause of periodicity : Periodicity may be defined as the repetition of the similar properties of the elements placed in a group and separated by certain definite gap of atomic numbers.

The cause of periodicity is the resemblance in properties of the elements is the repetition of the same valence shell electronic configuration.

7. Modern Periodic Table

Moseley proposed this modern periodic table and according to which “the physical and chemical properties of elements are periodic function of their atomic number and not the horizontal rows called “periods”. The groups have been numbered 1, 2, 3 …. 18 from left to right.

(ii) The elements belonging to a particular group make a family and usually named after the first member. In a group all the elements contain the same number of valence electrons.

(iii) In a period all the elements contain the same number of shells, but as we move from left to right the number of valence shell electrons increases by one unit.

The maximum number of electrons that can be accommodated in a shell can be calculated by the formula 2n2 where n is the number of the given shell from the nucleus.

8. Trends in Modern Periodic Table : The trends observed in some important properties of the elements in moving down the group (from top to bottom of the table) and across a period (from left to right in a period) are discussed below :

(i) Valency : Valency may be defined as the combining capacity of the atom of an element with atoms of other elements in order to acquire the stable configuration (i.e. 8 electron in valence shell. In some special cases it is 2 electrons).

(ii) Atomic size : It refers to the distance between the centre of nucleus of an isolated atom to its outermost shell containing electrons.

The atomic radius decreases on moving from left to right along a period. This is due to an increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom.

In a group atomic size decreases from top to bottom due to increase in number of shells.

(iii) Metallic and non-metallic properties : In a period from left to right metallic nature decreases while non-metallic character increases.

In a group metallic character increases from top to bottom while non-metallic character decrease.

(iv) Electronegativity : The relative tendency of an atom to attract the shared electron pair of electrons towards itself is called electronegativity.

In a period from left to right, the value of electronegativity increases while in a group from top to bottom the value of electronegativity decreases.

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Carbon and its Compounds, class 10th

Carbon and its Compounds

Science Class 10 Notes for Carbon and its Compounds

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.

Characteristics of covalent compounds :

(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.

In case a functional group is present, it is indicated in the name of the compound with either as a prefix or as a suffix.

While adding the suffix to the word root the terminal ‘e’ of carbon chain is removed If the carbon chain is unsaturated then the final `ane’ in the name of the carbon chain is substituted by ‘en& or yne’ respectively for double and triple bonds.

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.

(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.

2. Reaction with conc : H2SO4 :

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)

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.

14. Soaps and Detergents :

Soaps : Soaps are sodium or potassium salts of long chain acid carboxylic acids.

Detergent : They are ammonium or sulphurate salts of long chain carboxylic acids.

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Metals and Non-Metals, class 10th

Metals and Non-Metals for Class 10th

Some Important Notes

Introduction

In our day to day life we use many well-known materials like iron, aluminum, copper, gold, silver and many more. We are also familiar with the elements like oxygen, carbon, Sulphur as well. These are all obtained from some naturally occurring substances encompassing one or more elements or their compounds. They are termed as minerals. Minerals form which elements can be profitably extracted are termed as ores.

   

There 92 well known naturally occurring minerals of which 70 are metals and rets 20 are the non-metals.

Some metals possess the characteristics of both metals as well as non-metals. They are termed as metalloids. For instance, boron, silicon, germanium, arsenic, antimony, tellurium, and polonium.

Elements found in free state includes some metals like gold, silver, platinum etc. and some non-metals like helium, neon, argon etc. as well.

A major proportion of metals are found in combined states like oxides, sulphides, carbonates, silicates etc. Some non-metals like sulphur, phosphorous too are found to exist in combined state.

Physical properties of metal

Metals are solid except mercury that is found in liquid state at room temperature.

               

They are hard and tough except sodium and potassium that can be cut with a knife.

They are lustrous i.e. they shine in light because metals possess free electrons that vibrates on getting in contact with light.

They have high melting points except caesium and gallium have very low melting point.

They are good conductors of heat and electricity. The best conductors of electricity are silver and copper whereas lead and mercury are comparatively poor conductors.

They have high density except alkali metals like lithium, sodium and potassium.

They are malleablee. they can be beaten into thin sheets. For instance, the aluminium foil we use to pack food is manufactured by beating the aluminium metal into thin sheets. This a characteristic property of metal.

They are ductile. they can be drawn into wires. For instance. We all are familiar with copper and aluminium wires. It is due to their characteristic property of ductility that these metals can be drawn into wires.

They are sonorouse. they produce a ringing sound when struck against a hard object. For instance, your school bells are made of metal that produces a ringing sound after the period is over when struck hard by a hammer.

Examples are iron, gold, silver, magnesium, copper, aluminium and many more.

Physical properties of non-metals

Non-metals may be either solids, liquids or gases.

Solid non-metals are brittle and break down into powdery mass on striking with a hammer except diamond which is the hardest non-metal.

They have a dull luster but iodine is lustorous.

They have low melting points except diamond that has very high melting point.

They are poor conductors of heat and electricity except graphite.

They are not malleable.

They are not ductile.

They are not sonorous.

Examples are carbon, Sulphur, oxygen, phosphorous and many more.

Reactions of metal with oxygen

Metals reacting with oxygen is observed in our day to day life. We all must have observed rusting of iron, silver jewellery getting tarnished, or copper articles getting covered by green layer. Metals reacts with atmospheric oxygen and produces metal oxides that are basic in nature because they react with water to form bases.

In case of rusting of iron, the iron reacts with the oxygen present in air and moisture and develops rust (hydrated iron (III) oxide).

In case of rusting of copper, the metallic copper reacts with oxygen, carbon-dioxide and atmospheric moisture and develops a green coloured coating of copper hydroxide and copper carbonate.

In case of tarnishing of silver articles, the metallic silver reacts with hydrogen sulphide or sulphur present in air and gets tarnished.

Copper burns in air to combines with oxygen and form copper (II) oxide, a black oxide.

Exceptions to metallic oxides being basic in nature

Aluminium forms aluminium oxide.

And show both acidic as well as basic actions. Such metal oxides reacting with both acids as well as bases to produce salts and water are known as amphoteric oxides.

Metallic oxides are generally insoluble in water but some of the metallic oxides like Sodium oxide and potassium oxide dissolves in water to produce alkalis.

At normal temperature, the surfaces of metals such as magnesium, aluminium, zinc, lead, etc., develops a coating of thin layer of oxide. The protective oxide layer prevents the metal from further oxidation.

Magnesium burns in air to form magnesium oxide.

       2Mg + O2 --> 2MgO

Iron does not burn on heating but iron filings burn vigorously when scattered

in flames.

Copper does not burn on heating , but the hot metal develops a coating of black coloured copper(II) oxide.

        2Cu + O2 ---> 2CuO

Silver and gold do not react with oxygen even at high temperatures.

Reactions of metal with water

Sodium being very reactive reacts vigorously with water leading to the production of sodium hydroxide and hydrogen. Therefore it is stored in kerosene.

          2Na + 2H2O à 2NaOH + H2

Magnesium does not react with cold water. Magnesium undergoes reaction with hot water to form magnesium hydroxide and hydrogen.

        Mg +H2O à Mg(OH)2 + H2

  

The reaction of calcium with water evolves heat that is not sufficient for the hydrogen to catch fire.

          Ca (s)  + 2H2O(l) à Ca(OH)2 (aq) + H2 (g)

Whereas metals like aluminium, iron and zinc reacts neither with cold nor

hot water. Instead they react with steam to form the metal oxide and hydrogen.

Metals including lead, copper, silver and gold do not react with water at all.

Reactions of metal with acids

Metals react with acids to produce hydrogen gas. If a matchstick is brought near the mouth of the tube containing the product of the reaction then we hear a pop sound. It is this hydrogen gas that burns with a pop sound.

For instance, Magnesium reacts with dilute hydrochloric acid to form magnesium chloride and hydrogen.

Mg + 2HCl --> MgCl2 + H2

Copper does not react with hydrochloric acid but reacts with sulphuric acid.

CuO + H2SO4 --> CuSO4 + H2O

Hydrogen gas is not evolved when a metal reacts with nitric acid. This is due to the fact that HNO3 is a strong oxidising agent. It oxidises the H2 produced to water and gets reduced to any of the nitrogen oxides (N2O, NO, NO2). But magnesium (Mg) and manganese (Mn) react with very dilute HNO3 to evolve H2 gas.

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Acids, Bases and Salts, class 10th

Acids, Bases and Salts for Class 10th

X

Chemistry

Chapter 2

Acids, Bases and Salts

Chapter Notes

Top concepts:

1.Methyl orange: Methyl orange turns pink in acids and becomes yellow in bases.

2. On the basis of origin, acids are classified as:

a. Organic acids: Acids derived from living organisms like plants and animals are called organic acids. They are weak acids and are not harmful for living organisms. For example: citric acid is present in fruits, acetic acid present in vinegar, oxalic acid present in tomato, tartaric acid present in tamarind, lactic acid present in sour milk and curd.

b. Mineral acids: They are also called inorganic acids. They are dangerous and corrosive. Special precautions have to be taken while handling them. For example: sulphuric acid (H2SO4), hydrochloric acid (HCl) etc.

3. On the basis of their strength, acids are classified as:

a. Strong acids: Strong acids are those acids which completely dissociate into its ions in aqueous solutions. Example: nitric acid (HNO3) , sulphuric acid(H2SO4), hydrochloric acid(HCl)

b. Weak acids: Weak acids are those acids which do not completely dissociate into its ions in aqueous solutions. For example: carbonic acid (H2CO3), acetic acid (CH3COOH)

4. On the basis of their concentration, acids are classified as:

a. Dilute acids: Have a low concentration of acids in aqueous solutions.

b. Concentrated acids: Have a high concentration of acids in aqueous solutions.

5. Alkalies: Water soluble bases are called alkalies. For example: Sodium hydroxide (NaOH), potassium hydroxide(KOH)

6. On the basis of their strength, bases are classified as:

a. Strong bases: Strong bases are those bases which completely dissociate into its ions in aqueous solutions. Example: sodium hydroxide (NaOH), potassium hydroxide (KOH)

b. Weak bases: Weak bases are those bases which do not completely dissociate into its ions in aqueous solutions. For example: ammonium hydroxide (NH4OH)

7. On the basis of their concentration, bases are classified as:

a. Dilute bases: Have a low concentration of alkali in aqueous solutions.

b. Concentrated bases: Have a high concentration of alkali in aqueous solutions.

8. Acids and bases conduct electricity because they produce ions in water. There is a flow of electric current through the solution by ions.

9. Indicators are those chemical substances which behave differently in acidic and basic medium and help in determining the chemical nature of the substance. Acid base indicators indicate the presence of an acid or a base by a change in their colour or smell.

10.Indicators can be natural or synthetic.

11.Olfactory indicators: These are those indicators whose odour changes in acidic or basic medium. Example: onion

12.Onion: Smell of onion diminishes in a base and remains as it is in an acid.

13.Vanilla essence: The odour of vanilla essence disappears when it is added to a base. The odour of vanilla essence persists when it is added to an acid.

14.Turmeric: In acids, yellow colour of turmeric remains yellow. In bases, yellow colour of turmeric turns red.

15.Litmus: Litmus is a natural indicator. Litmus solution is a purple dye which is extracted from lichen. Acids turn blue litmus red. Bases turn red litmus blue. Water is essential for acids and bases to change the colour of litmus paper. Remember that litmus paper will act as an indicator only if either the litmus paper is moist or the acid or base is in the form of aqueous solution. This is because acids and bases release H+ and OH- ions respectively in aqueous solutions.

16.Phenolphthalein: Phenolphthalein remains colourless in acids but turn pink in bases.

Some Important Questions of this Chapter

1. What are the symptoms of the problem of acidity? What possible remedy can be used at home?

2. Name three chemical indicators.

3. How does turmeric change its colour in an alkaline medium?

4. Write equations for the reaction of an acid with;

  (a) a metal (b) a metal carbonate (c) a metal hydrogencarbonate (d) a base (e) a metallic oxide.

5. On keeping curd in a brass vessel for sometime, it becomes bitter. Why?

6. What happens when an acid is dissolved in water?

7. Why is HCl gas unable to change the colour of a dry blue litmus paper? What happens if the litmus paper is moistened?

8. A solution of HCl in water conducts electricity but that of glucose in water does not. Why?

9. What is a hydronium ion? How is it formed?

10. Which ions are generated by bases in water?

11. For diluting an acid, the acid should be poured carefully in water and not the reverse. Why?

12. When an acid is mixed with water, what happens to:-

  (a) The conc. of hydronium ions per unit volume. (b) The conc. of hydroxide ions per unit volume.

13. Two solutions A & B have pH 2 and 6 respectively. Which is more acidic?

14. Name the hardest chemical substance present in our body.

15. How does acid rain water affect the survival of aquatic life?

16. Why does bee-sting cause pain and irritation? What relief can be given in such a case immediately?

17. From the following, pick the acidic, basic or neutral salts:- (a) Sodium chloride (b) Sodium acetate (c) Ammonium chloride (d) Calcium carbonate (e) sodium carbonate

18. What is chlor-alkali process?

19. How is baking soda & washing soda manufactured?

20. Explain the role of baking soda in baking powder.

21. What is meant by water of crystallization?

22. How can you show with an activity the presence of water in blue copper Sulphate crystals?

23. How is gypsum different from plaster of paris chemically?

24. Why should POP be stored in air tight containers?

25. Write 2 uses of: Washing soda, baking soda. bleaching powder.

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Chemical Reactions and Equations ,class 10th

Chemical Reactions And Equations For Class 10th 

Chemical Reactions And Equations: 

Balnced and unblanced chemical equations and balancing of cemical equatons.

Chemical Reaction:

The transformation of chemical substance into another chemical subsubstance is known as Chemical Reaction. For example: Rusting of iron, setting of milk into curd, digestion of food, respiration, etc.

In chemical reaction, new substance is formed which is completely different in properties from the original substance, so in a chemical reaction, chemical change takes place.

Only a rearrangement of atoms takes place in a chemical reaction.

(1) The substances which take part in a chemical reaction are called reactants.

(2) The new substances produced as a result of chemical reaction are called products.

Example: The burning of magnesium in air to form magnesium oxide is an example of chemical reaction.

    2Mg(s) + O2(g) ----> 2MgO(s)

Before burning in air, the magnesium ribbon is cleaned by rubbing with sand paper.

This is done to remove the protective layer of basicbasic magnesium carbonate from the surface of magnesium ribbon.

•Reactant: Substances which take part in a chemical reaction are called reactants. Example: Mg and O2.

•Products: New substances formed after a chemical reaction are called product. Ex: MgO.

Characterstics of Chemical Reactions:

(1) Evolution of gas: The chemical reaction between zinc and dilute sulphuric acid is characterised by the evolution of gas.

   Zn(s) + H2SO4(aq) ----> ZnSO4(aq)                                                 + H2(g)

(2) Change in colour: The chemical chemical reaction between citric acid and purple coloured potassium permanganate solution is characterised by a change in colour from purple to colourless.

The chemical reaction between sulphur dioxide gas and acidified potassium dichromate solution is characterised by a change in colour from orange to green.

(3) Change in state of substance: The combustion reaction of candle wax is characterised by a change in state from solid to liquid and gas (because wax is solid, water formed by the combustion of wax is a liquid at room tempreture whereas, carbon dioxide produced by the combustion of wax is a gas). There are some chemical reactions which can show more than one characteristics.

(4) Change in temperature: The chemical reaction between quick lime water to form slaked lime is characterised by a change in temperatue (which is rise in temperature).

The chemical reaction between zinc granules and dilute sulphuric acid is also characterised by change in temperature (which is rise in temperature).

(5) Formation of precipitate: The chemical reaction between sulphuric acid and barium chloride solution is characterised by the formation of a white precipitate of barium sulphate.

   BaCl2(aq) + H2SO4(aq) ----->                                      BaSO4(s) + 2HCl(aq) 

                            (ppt)

Some important Questions Of Chapter Chemical Reaction And Equations

1. Give 5 examples each of physical and chemical changes that take place around us in our day to day life.

2. When a magnesium ribbon is burnt in air, what are the two observations that you make?

3. Write a balanced chemical equation to represent decomposition of lead nitrate on heating. What are brown fumes due to?

4. Make a list of at least 10 cations and 10 anions.

5. Taking help from the list prepared in Q4,, write the chemical formulae of:-

  (i) Barium chloride (ii) Sodium Sulphate (iii) Ammonium phosphate (iv) Calcium hydroxide

  (v) Aluminium carbonate (vi) Magnesium hydrogen carbonate (vii) Zinc sulphide

  (viii) copper (׀) chloride (ix) Potassium Bromide (x) Lead nitrate (xi) Iron ( ׀׀׀) oxide (xii) Sodium Oxide (xiii) Silver sulphide (xiv) Calcium Fluoride

6. Write the following in the form of balanced chemical equations:-

  (a) Calcium carbonate decomposes on heating to form calcium oxide and carbon – di – oxide.

  (b) When ammonium hydroxide is added to a solvent of iron (ll) Sulphate, a green ppt of iron (ll) hydroxide and ammonium Sulphate are formed.

  (c) When a nail of iron is added to a solution of copper Sulphate, iron (ll) Sulphate and copper metal are formed.

  (d) Zinc reacts with dil hydrochloric acid to form zinc chloride and hydrogen gas is liberated.

7. A chemical reaction which is both combination as well as exothermic, is used by us for white washing purposes. Write the equation for the same.

8. What is a decomposition reaction? Give 2 examples each of decomposition taking place due to heat, light and electricity.

9. How does a displacement reaction differ from a double displacement reaction? Give examples to explain.

Some definitions of this chapter

Top definitions:

1. Chemical reaction: A chemical reaction involves a chemical change in which substances react to form new substances with entirely new properties. Substances that react or take part in the reaction are known as reactants and the substances formed are known as products. 

2. Physical change: If a change involves change in colour or state but no new substance is formed, then it is a physical change.

3. Chemical change: If a change involves formation of new substances, it is a chemical change.

4. Chemical equation: The symbolic representation of a chemical reaction is called a chemical equation.

5. Exothermic and endothermic reactions: If heat is evolved during a reaction, then such a reaction is known as exothermic reaction. If heat is absorbed from the surroundings, then such a reaction is known as endothermic reaction

6. Combination reaction: Combination reaction is a reaction in which 2 or more substances combine to give a single product.

7. Decomposition reaction: In a decomposition reaction, a single reactant decomposes to give 2 or more products. Decomposition reactions require energy in the form of heat, light or electricity

8. Displacement reaction: A reaction in which a more active element displaces less active element from its salt solution.

9. Reactivity series: The Reactivity series is a list of metals arranged in the order of decreasing reactivity. The most reactive metal is placed at the top and the least reactive metal is placed at the bottom.

10.Double displacement reaction: A chemical reaction in which there is an exchange of ions between the reactants to give new substances is called a double displacement reaction.

11.Precipitation reaction: An insoluble solid known as precipitate is formed during a double displacement reaction. Such reactions are also known as precipitation reactions.

12.Redox reaction: A reaction, in which oxidation and reduction takes place simultaneously is known as redox reaction.

13.Oxidation: Oxidation is a chemical process in which a substance gains oxygen or loses hydrogen.

14.Reduction: Reduction is a chemical process in which a substance gains hydrogen or loses oxygen.

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Hello Friends in Sceince Logic

I am Suraj Gour, and I welcomes you in science logic.

Here we explore the world of science. Nowadays ,we all are know that all things happend in our environment is all related to science. So our problems are also related to our works and science, we all of us try or think to solve our problems but many of them can't do that because we don't know the roots of our problems. To know the roots of our problem we have to explore science because all that is related to science.   

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