Class 10th science chapter 1 notes(EBOOK) | Class 10 chemical reactions and equations notes



Introduction

Class 10 chemical reactions and equations is the first chapter of NCERT science and according to the latest syllabus of cbse 2022-23 there is only two topics reduced in this chapter that is corrosion and Rancidity.

To Know more about the cbse class 10 2022-23 syllabus follow the link below


Class 10 chemical reactions and equations notes that we are providing you is the best and detailed notes ever provided on our website.

Topics we are going to cover:-

  • Introduction to Chemical Reactions
  • Characteristics of Chemical Reactions
  • What are Chemical Equations?
  • Balancing Chemical Equations
  • Types of Chemical Reactions
  • Rancidity and it's prevention
  • Corrosion and it's prevention

Chemical Reactions & Equations Notes(EBOOK LINK BELOW)

Introduction of Chemical Reaction


We have often seen that some substances when mixed, form new substances.




Like if we want to make tea, we add sugar, tea, milk and water. On heating, it turns into tea.


Likewise, if you add a spoon of curd to lukewarm milk and keep it aside for a few hours, then the whole milk turns into curd..


We conclude that they thoroughly mix with each other and form a new substance. This thorough mixing is a chemical reaction.



Chemical reaction


Definition: When two or more substances react and form some new substance, it is called a chemical reaction.


Let us see few activities related to chemical reaction:


1. Burning of magnesium ribbon: the magnesium ribbon we bring has a layer of carbonate on it so before burning it needs to be cleaned with sandpaper.


Products: magnesium oxide (white color_MgO)


Identification property of reaction: white dazzling flame

Magnesium ribbon be like:-

2. Reacting zinc granules with dilute sulphuric acid


Chemical reaction: H2S04+Zn—>ZnSO4+H2


Products: zinc-sulphate and hydrogen gas


Identification: beaker becomes hot and hydrogen gas is produced which makes matchsticks burn with pale blue flame and popping sound.

3.Reacting barium iodide with lead chloride 


Chemical reaction: Bal+PbC12->BaCL2+Pb


Products: barium chloride white color and yellow color precipitate of lead iodide.


Characteristics of a chemical reaction


1. It is accompanied by a change in colour.


2. It either leads to a change in state. 


3. Heat energy is produced or absorbed.


4. Precipitate is formed. 


5. Gas is released.



Chemical Equation and Balancing


Chemical equation: it is the representation of chemical reaction in terms of symbols, molecular formulas, moles, states, etc. 


As we know, all chemical reactions obey the law of chemical combination. Therefore, chemical reactions need to be balanced. It is done by hit and trial method. (For practice, questions are solved in the end)


Types of chemical equations


We come across different types of reactions that occur in nature.

Let us study about their type in detail:


Combination reaction 

when two or more reactants react to form a single product.



ie A+B-AB (In this one single product is formed) This reaction can be between element-element, element-compound or compound-compound.



Like

H2

+

Cl2

-

HCL


(E)


(E)


(Product)








SO2

+

O2

-

SO3


(C)


(E)


(Product)








CO2

+

H2O

-

H2CO3


(C)


(C)


(Product)


Let us see an activity to demonstrate a combination reaction 

Burning of magnesium ribbon is an activity of combination reaction









Burning of magnesium ribbon: 

The magnesium ribbon we bring has a layer of carbonate on it so before burning it needs to be cleaned with sandpaper. Products: magnesium oxide (white color_Mgo) 

Identification property of reaction: white dazzling flame



Decomposition reaction 

it is the type of reaction in which a reactant breaks up into its constituents either by heating or passing current or in presence of light.


i.e.,


1.Photodecomposition (breaking in presence of light 



Example

AgCl

Ag

+

Cl2


(White)


(Grey)




(b) Electrolytic decomposition: breaking by passing current



Example

NaCl

Na

+

Cl2



(c) Thermal decomposition (breaking by heating)



Example

Pb(NO3)2

PbO

+

NO2

+

O2






(Reddish brown gas)




Activity To Demonstrate: heating of ferrous sulphate FeSO4.7H20-FeS04+7H20 (green)


FeS04 - -heat → Fe203+So2+S03



 Displacement reaction 

it is a reaction between element and a compound in which more reactive element displaces less reactive from its compound



i.e. In this we follow the reactivity series. Examples:



Activity To Demonstrate reaction of zinc granules with dilute sulphuric acid is an example of displacement reaction



Double displacement reaction 

it is a reaction between two compounds in which they mutually exchange their ions.


i.e.



A and C are Cations (Positive ions) 

B and D are Anions (Negative ions)


This is either precipitation reaction or neutralization reaction.


Precipitation reaction 

The reaction in which two compounds mutually react and leads to formation of insoluble substances called precipitates.



Bal

+

PbCl2

BaCl2

+

Pbl2





(Yellow colour) 






Neutralisation reaction


A reaction in which two compounds react to form a neutral substance.


i.e. Acid +Base → salt +Water

HCl+NaOH-NaCl+H20

Example:



Let us learn about oxidation and reduction


Oxidation Reaction

addition of oxygen or removal of hydrogen 


Mg + O2 → MgO

NaH →  Na + H2


Reduction Reaction

 addition of hydrogen or removal of oxygen


Na + H2 → NaH

MgO → Mg + O2


Oxidising agent: which oxidised other and itself get reduced


Reducing agent: which reduces other and itself get oxidised 


In this equation

Mg + O2 MgO


Mg is reducing agent and O is oxidising agent


On the basis of electronic concept

Oxidation: which donate electrons 

Reduction: which gains electrons 

Redox reaction: The reaction in which oxidation and reduction takes place simultaneously


Cuo + H2 → Cu + H2O

In this, Cu (Oxidising agent) Is getting Reduced and Hydrogen (Reducing agent) Is getting Oxidised.


Daily life redox reaction: In daily routine we come across many Redox reactions. Out of it we are going to learn about two important reactions:


Reduced part:

  • Rancidity
  • Corrosion

Rancidity


We have seen mostly in summers that if we keep any food item at room temperature for longer time, it becomes stale. It is due to the oxidation of food when it comes in contact with air due to which it starts smelling bad and tastes bad. We can prevent it by taking few precautions like storing food in refrigerator. It will slow down the activity of microorganisms due to which their shelf life increases.

Prevention:


1. Storing at low temperature

2. Adding preservative like salting, sugaring, nitrogen gas in potato chips, etc


Corrosion


it is eating away of metal article.

In case of iron it is called rusting. Conditions required : moist air 

Chemical reaction: fe+02->Fe203.xH20

                               (brown color rust)










Prevention of rusting


  • Painting 
  • Lubricating
  • Galvanisation: it is the process of depositing thin layer of Zn on iron article. By doing it Zn prevent the reaction of iron with moist air.
  • Electroplating: by the process of electrolysis Cu and Cr layers are added on iron articles. 
  • Alloying: we can use the alloy of iron i.e. stainless steel.









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Class 10 Chemical Reactions and Equations Notes EBOOK



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