Class - 10 Chemical Reaction and Equations Chapter Notes

Class - 10

Science Chemistry

Chapter :- 1

Chemical Reaction and Equations

Notes

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Physical Change :-

These are the changes which can be reversed.

Example- Freezing of water.

 

Chemical Change :-

These are the changes which cannot be reversed.

Example- Rusting of iron.

 

Reactant :-

The substance which take part in chemical reaction are called reactants.

 

Products :-

The substance which are formed in the chemical reaction are called products.

Example- Na + H₂O → NaOH + H₂

 

Chemical Reaction :-

The chemical reaction is the process in which two or more substances combine to form new substance.

Example- H₂ + O₂ → H₂O

 

Changes occur during a chemical Reaction :-

     1.     Change in state

     2.     Change in color

     3.     Evolution of gas

     4.     Change in temperature

     5.     Formation of a precipitation

 

What is Chemical Equation?

Chemical Equation is the symbolic representation of a chemical reaction with the help of symbols and formulas.

Example- CH₄ + O₂ → CO₂ + H₂O

 

What is Balance Chemical Equation?

The equation in which the number of atoms in the reactant and product are same is called balanced chemical equations.

 

Why do we need to balance Chemical Equations?

According to law of conservation of mass, mass can be neither created nor be destroyed during a chemical reaction.

 

 

Types of Chemical Reaction :-

     1.   Combination reaction

     2.   Decomposition reaction

     3.   Displacement reaction

     4.   Double displacement reaction

     5.   Exothermic and Endothermic reaction

 

1.  Combination Reaction :-

The reaction in which two or more reactants combine to form a single products is called combination reaction.

 

Example-

     a.  Formation of water:-

     2H₂ + O₂ → 2H₂O

     b.  Burning of coal:-

          C + O₂ → CO₂

 

 

2.  Decomposition Reaction :-

The reaction in which a single reactant breakdown to form two or more products.

 

A. Thermal Decomposition :-

Decomposition which is done by heat, we call it thermal decomposition.

 

Example- CaCO₃ → CaO + CO₂

 

 

B.  Electrolytic Decomposition :-

Decomposition which is done be electricity we call it electrolytic decomposition.

 

Example- 2H₂O → 2H₂ + O₂

 

 

C. Photolytic Decomposition :-

Decomposition which is done with the help of light energy, we call it photolytic decomposition.

 

Example- 2AgCl → 2Ag + Cl₂

 

 

 

3.  Displacement Reaction :-

     The reaction in which more reactive elements displaces less reactive elements from its compound or solution is called displacement reaction.

     Example- Zn + CuS₄ → ZnS₄

 

 

 

4.  Double Displacement Reaction :-

The reaction in which two different ion or group of atom in the reactant molecules are displace by each other is called double displacement reaction.

 

Example- AgNO₃ + NaBr → AgBr + NaNO₃

 

 

 

5.  Oxidation and Reduction Reaction :-

Oxidation Reaction :-

The process in which ;-

a.  Oxygen is added to a substance

b.  Hydrogen  is removed from a substance

c.   Substance loss electron

Example- 2Cu + O₂ → 2Cu₂O

     2H₂S + O₂ → 2H₂O + 2S

     Zn → Zn²⁺ + 2^e- _­

Reduction Reaction :-

The process in which :-

a.  Oxygen is removed from a substance

b.  Hydrogen is added to a substance

c.   Substance gain electron

 

Example- 2KClO₃ → 2KCl + O₂

      2Na + H₂ → 2NaH

      Zn²⁺ + 2^e- → Zn

 

 

 

Redox Reaction :-

The reaction in which oxidation and reduction take place simulation take place simultaneously are called redox reaction.

Example- CuO + H₂ → Cu + H₂O

 

6.  Exothermic and Endothermic Reaction :-

Exothermic Reaction :-

The reaction are accomplished by evolution of heat are called exothermic reaction.

 

Example- Burning of Natural Gas

               CH + 2O₂ → CO₂ + 2H₂O + Heat

 

Endothermic Reaction :-

The reaction which occur by the absorption of heat energy  are called endothermic reaction.

 

Example- 2HgO + Heat → 2Hg + O₂

 

 

Effects of oxidation in our daily life :-

1.   Corrosion

2.   Rancidity

 

1.  Corrosion :- The phenomenon due to which metals are slowly eaten away from the reaction of air, water, and other chemical present in atmosphere is called corrosion.

 

Example - Black Coating on silver

              - Green Coating on copper

              - Rusting of Iron

        

Effects of Corrosion :- Car bodies, Bridges, Iron Railways, Ships, other materials are damaged.

 

 

 

2.   Rancidity :- It is the process of slow oxidation for oil and fat present in the food material.

Methods to prevent Rancidity :-

a.  Keeping food material in air tight containers.

b.  Refrigeration of cooked food at low temperature.

c.   Avoid keeping the cooked food and food materials in direct sunlight.