Class 10, NCERT (CBSE) Chemistry Notes and Sample (Hot) Questions | Chapter 1, Chemical Reactions and Equations

Ncert Cbse Class 10, Science (Chemistry) 

 Chemical Reactions and Equations

Science Notes

What is a ‘Reaction’?

Reaction is a term used for depicting a change or transformation in which a substance decomposes, combines with other substances, or interchanges constituents with other substances.

What is a ‘Chemical Reaction’?

A chemical change is always accompanied by a chemical reaction. a chemical change or reaction can be confirmed by any or all of the following observations:

=> change in state

=> change in colour

=> change in temperature

=> evolution of gas.

What is a ‘Chemical Equation’?

A Chemical Equation represents a chemical reaction. A complete chemical equation represents the reactants, products, and their physical states symbolically. A chemical equation also indicates a number of atoms of each element involved in a reaction. A chemical equation can be written as balanced or unbalanced. An unbalanced chemical equation is also known as Skeletal Chemical Equation for a reaction. An equation having an equal number of atoms of each element on both the sides is called a balanced chemical equation.

Types of Chemical Reaction

Chemical Reactions are primarily of five types as listed below:

1. Combination reaction

2. Decomposition reaction

3. Displacement reaction

4. Double displacement reactions

5. Oxidation and Reduction reactions

What are ‘Combination Reactions’?

When two or more substances (elements or compounds) combine to form a single product, the reactions are called ‘Combination Reactions’. Generally, Combination Reactions are exothermic in nature. The following are some examples of Combination Reactions:

CaO (s) + H₂O (l) -----> Ca(OH)₂ (aq)

C (s) + O₂ (g) ------> CO₂ (g)

What are ‘Decomposition Reactions’?

Decomposition reactions are opposite to combination reactions. In a Decomposition reaction, a single substance decomposes to give two or more substances.

What are ‘Displacement Reactions’?

When an element displaces another element from its compound, such reaction is called a displacement reaction e.g. -

Zn (s) + CuSO₄ (aq) -----> ZnSO₄ (aq) + Cu (s)

What are ‘Double Displacement Reactions’?

A double displacement reaction is a bimolecular process in which parts of two compounds are exchanged to give two new compounds. The general equation used to represent double displacement reactions can be written as -

AB + CD -----> AD + BC

Examples of double displacement reactions are -

Na₂SO₄ (aq) + BaCl₂ (aq) -----> BaSO₄ (s) + 2NaCl (aq)

“Double Displacement Reactions” have two commoj features -

1. Two compounds exchange their ions resulting in the formation of two new compounds.

2. One of the new compounds formed would be separated from the mixture in some way, commonly as a solid or gas.

Double displacement reactions can be further classified as Precipitation, Gas formation, and Acid-base neutralization reactions.

Sample Hot Questions

Q.1: Which of the following is a Combination and which is a Displacement Reaction?

(a) Cl₂ + 2KI -----> 2KCl + I₂

(b) 2K + Cl₂ ------> 2KCl

Ans:

(a) Displacement reaction

(b) Combination reaction

Q.2: What is a catalytic decomposition?

Ans: Those reactions in which a compound splits up into two or more simpler substances in the presence of catalyst are called catalytic reactions. For example, digestion of food in human body.

Q.3: What is the term used for the symbolic representation of a reaction.

Ans: Chemical equation.

Q.4: Write two uses of decomposition reactions.

Ans: Two uses of decomposition reactions -

(i) These reactions are used to extract several metals from their oxides and salts. When the oxide or salt is electrolyzed, metal is obtained as per the following equation:

2Al₂O₃ ------> 4Al + 3O₂

(ii) Digestion of food in our body is also an example of decomposition reaction. The starch (carbohydrates) present in the body is decomposed to give simple substance (glucose) and the proteins are broken down into amino acids.   

Q.5: Explain the terms ‘oxidizing agent’ and reducing agent’.

Ans:

Oxidizing agent

The substance, which oxidizes elements or compounds, is known as oxidizing agent e.g. -

4Fe + 3O₂ ------> 2Fe₂O₃

Hence, oxygen is an oxidizing agent. In this equation it oxidizes iron (Fe^II) to ferric oxide (Fe₂O₃).

Reducing agent

The substance, which oxidizes elements or compounds, is known as oxidizing agent e.g. -

SnCl₂ + 2FeCl₃ -----> SnCl₄ + 2FeCl₂

Here stannous chloride is a reducing agent. It reduces ferric chloride to ferrous chloride.    

Further Study on Chapter 1, Chemical Reactions and Equations  

• Chemical Reactions and Equations | Class 10 NCERT (CBSE) Science (Chemistry) Textbook In-Text Questions - Answers 
• Class 10, CBSE (NCERT) Science | Chapter-1, Chemical Reactions and Equations | NCERT Solution - Science Textbook Exercise 
• Class 10 NCERT (CBSE) Science Chemistry - Multiple choice questions (MCQ) | Chapter 1,  Chemical Reactions and Equations

Ncert Our Past II Class VII History | Towns, Trades and Crafts Persons | Sample Questions (Cbse Cce pattern)

Class 7, Towns, Trades and Crafts Persons

Sample Hot Questions based on NCERT textbook following CBSE syllabus, CCE pattern 

Short type Questions with their Answers

Q.1: What were the kinds of towns in the medieval period? Or, For what purposes towns were made in the medieval period?

Answer: During the medieval period the towns were of many kinds which were made for 

various functions: 

• The town used to be a temple town, administrative center, a commercial town or a port town.
• In fact, many towns combined several functions. They were administrative centers, temple towns, centers of commercial activities and craft production.

Q.2: Give an account of administrative centers of the Chola Dynasty (in the medieval period), especially the Thanjavur.

Answer: Administrative Centers of the Chola Dynasty: 

1. During the rule of the Chola dynasty Thanjavur was the capital a thousand years ago. 
2. The perennial river Kaveri flows near this beautiful town. The Rajarajeshvara temple was built by king Rajaraja of Chola dynasty. 
3. The town’s people are all praised for its architect Kunjaramallan Rajaraja Perunthachchan. He proudly carved his name on the temple wall. Inside is a massive Shiva Linga. 
4. Along with the temple, there are palaces with Mandapas or pavilions. 
5. Kings held court in these mandapas. They issued orders to their subordinates. 
6. There are also Barracks for the army.

Q.3: Describe temple-towns and pilgrimage centers.

Answer: Temple-Towns and Pilgrimage Centers: 

• Temple towns represent a very important pattern of urbanization. For example, Thanjavur is a temple town and so an important pilgrimage center. 
• Urbanization is the process by which cities develop. 
• Temples were often central to the economy and society: (i) rulers built temples to demonstrate their devotion to various deities. (ii) they also endowed temples with grants of land & money to carry out elaborate rituals, feed pilgrims etc. 
• Pilgrims also made donations.

Q.4: Why did European sailors undertake voyages to the Indian subcontinent in the 15^th century?

Answer: In the 15^th century European sailors undertook difficult voyages of sea routes. They were driven by the desire to find ways of reaching the Indian subcontinent and obtaining spices.

Q.5: Give an account of the Journey of Columbus.

Answer: On the assumption that the earth was round, Christopher Columbus, an Italian sailor, decided to sail westwards across the Atlantic Ocean to find a route to India. But he landed in the West Indies. He was followed by sailors and conquerors from Spain and Portugal, who occupied large parts of central & South America, often, destroying earlier settlements in the area. 

Long type Questions with their Answers

Q.1: Give an account of Hampi.  

Answer:

• The architectural splendor of Hampi: It is located in the Krishna-Tungabhadra basin. It was the centre of the Vijayanagara Empire. The magnificent ruins at Hampi reveal a well - fortified city. 
• The architecture of Hampi was distinctive. The buildings in the royal complex had splendid arches, domes and pillared halls with niches for holding sculptures, with well planed orchards and pleasure gardens. 
• Hampi was famous for commercial and cultural activities. 
• Moors, chettis and agents of European traders like the Portuguese, thronged the market of Hampi. 
• The Mahanavami festival was one of the most important festivals celebrated at Hampi. Archeologists have found the Mahanavami platform where the king ereceived guests and accepted tributes from subordinate chiefs. 
• Hampi fell into ruin following the defeat of Vijayanagara in 1565 by the Deccani Sultans. The sultans included the rulers of Golconda, Bijapur, Ahmednagar, Berar and Bidar.

Q.2: Describe Surat as a gate-way to the west.

Answer: Surat in Gujarat was the emporium means, showcase of Western trade during the Mughal period. Surat was the gate-way for trade with West Asia via the gulf of Ormuz. Surat is also called the gate to Mecca because many pilgrim ships set sail from here. The city was cosmopolitan. People of all casts and creeds lived there. In the 17^th century the Portuguese, Dutch and English had their factories and warehouses at Surat. There were also several retail and whole-sale shops selling cotton textiles. The textiles of Surat were famous for their gold lace borders (Zari). They had a market in West Asia, Africa and Europe. Surat hundis were honoured in the far off markets of Cairo in Egypt, Basra in Iraq and Antwerp in Belgium. The factors responsible for decline of Surat were mainly the –

• Loss of markets and productivity as a result of the decline of the Mughal Empire. 
• Control of the sea routes by the Portuguese. 
• Competition from Mumbai where the English East India Company shifted its head quarters in 1668.

Q.3: Describe the voyage of Vasco-da-gama.

Answer: Vasco-da-gama, a Portuguese sailor, was one of those who sailed across the Atlantic to the African coast. He went round it, crossing over to the Indian Ocean. He reached Calicut in 1498, and returned to Lisbon. During his voyage he lost two of his four ships and of the 170 men at the start of the journey, only 54 survived. In spite of the obvious hazards, the routes that were opened up proved to be extremely profitable. English, Dutch and French sailors followed him. 

   

Towns, Trades and Crafts Persons | Class VII, NCERT (CBSE) Social Science |  Chapter 6, Our Past II - NCERT Solutions for Textbook Exercise Questions

CBSE (NCERT) Class X Geography - Contemporary India II | Chapter - 1, Resources and Development | Intext and Sample Questions

Class 10 Ncert Cbse Geography | Contemporary India - II

RESOURCES AND DEVELOPMENT

 Activities and NCERT textbook In-Text Questions

Q.1: Identify at least two resources from each category.

Ans:

Biotic resources - 1. human beings, 2. natural vegetation.

Abiotic resources - 1. water, 2. coal, 3. petroleum.

Renewable resources - 1. forests, 2. solar energy.

Non-renewable resources - 1. coal, 2. CNG.

Individual resources - 1. land, 2. house.

Community resources - 1. grazing grounds, 2. public parks.

National resources - 1. minerals, 2. river water.

International resources - 1. resources from ocean water and sea-bed beyond 200 km. of EEZ, 2. sea-routes

Potential resources - 1. tidal energy, 2. geothermal energy.

Developed resources - 1. coal 2. water.

Stock resources - 1. unexplored energy present in the interior of the earth, 2. hydrogen  and oxygen from water.

Reserves - 1. forests, 2. water in dams.    

Q.2: Can you name some resource-rich but economically backward regions and some resources poor but economically developed regions. Give reasons for such a situations.  

Ans: Regions rich in resource but backward

1)    Jharkhand is rich in mineral resources but still it is economically backward due to the following reasons:

a.    illiteracy

b.    scarcity of agricultural land

c.       lack of small scale industries

d.    disparity in income among the people

2)    Assam is rich in minerals like - coal and petroleum, cultivable land, forests and water resources but is still economically backward. The reasons are:

a.    various tribal groups who reside in this region are poor and orthodox

b.    terrorism and insurgency

c.      floods occurring almost every year

  Regions poor in resources but economically rich

Delhi is poor in resources but still it is economically rich because it is the administrative capital of India. Due to the availability of properly developed infrastructure it is industrially rich as well as most of the head offices of various government organizations are also situated here.      

Q.3: Why is conservation of resources important?

Ans: Irrational consumption and over-utilization of resources lead to socio-economic and environmental problems. If natural resources are not used judiciously then, it will cause a stagnation of development after a point of time. Exploiting resources unethically will ultimately undo the development that a country may have achieved as in future those resources will not be available for further progress. 

Q.4: The pattern of net sown area varies greatly from one state to another. It is over 80% of the total area in Punjab and Haryana and less than 10% in Arunachal Pradesh, Mizoram, Manipur and Andaman Nicobar Islands.

Find out reasons for the low proportion of net sown area in these states.   

Ans: Reasons for the low proportion of net sown area in Arunachal Pradesh, Mizoram, Manipur and Andaman Nicobar Islands are as follows:

1. Mostly tribal group lives in this region. Even today they practice shifting cultivation.

2. These states are covered by dense tropical forests.

3. These states receive very heavy and a large amount of rainfall.

4. The topography and soil types are not favourable for the cultivation.

5. These states are still considered as backward where the farmers or peasants are economically poor and do not have access to technological resources. 

Additional Important Sample Questions (CCE pattern)

Q.5: What are resources?

Ans: Everything available in our environment which can be used to satisfy our needs provided it is technologically accessible, economically exploitable and culturally acceptable, can be termed as resource.   

Q.6: Why are the human beings essential components of resources?

Ans: Human beings are essential components of resources because it is the human beings who transform the material available in our environment into resources and use them. In fact, resources are a function of human activities. 

Q.7: How are the resources classified on the basis of origin and exhaustibility?

Ans: Classification of resources on the basis of origin

1. Biotic

2. Abiotic

Classification of resources on the basis of exhaustibility

1. Renewable

2. Non-renewable

Q.8: Classify the resources on the basis of ownership and status of development.

Ans: Classification of resources

(i) On the basis of ownership:

1. Individual

2. Community

3. National

4. International

(ii) On the basis of status of development:

1. Potential

2. Developed (Reserve)

3. Stock  

Resources and Development | CBSE Class X, Social Science (Geography) | Chapter 1, Contemporary India - II | NCERT Textbook Exercise Solutions Read