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Class 9 Social Science Chapter 1 Notes | Understanding Social Science | NCERT 2026–27 | Understanding Society: India and Beyond

Chapter 1: Understanding Social Science

Topic 1: What Is Social Science?

What Is Social Science?

Introduction

Human beings do not live alone. They live in families, villages, towns, cities, states and countries. They interact with nature, use resources, form governments, develop cultures, exchange goods, create traditions and solve problems together.

The study of all these human activities is known as Social Science.

Social Science helps us understand how people live, think, work, govern, produce, trade and interact with each other and with their environment. It explains not only what happened in the past but also why it happened, how it affects the present and how it can influence the future.

Unlike natural sciences, which study nature and physical objects, Social Science studies human society and human behaviour.

Definition of Social Science

Social Science is the systematic study of human society, human behaviour, relationships, institutions, cultures, economies, governments and the interaction between people and their environment.

Simple Definition

Social Science is the study of people, society and the world in which they live.

Meaning of Social Science

The word Social refers to people living together in society.

The word Science means knowledge obtained through careful observation, investigation, evidence and logical reasoning.

Therefore,

Social Science means the scientific study of society using facts, evidence and logical thinking.

Social scientists do not depend only on opinions or guesses. They collect information, analyse evidence, compare different viewpoints and then reach conclusions.

Why is Social Science Called a Science?

Many students think only Physics, Chemistry and Biology are sciences.

However, Social Science is also a science because it follows a systematic method.

Social scientists

  • Observe society carefully.
  • Collect evidence.
  • Study historical records.
  • Conduct surveys.
  • Analyse data.
  • Compare different situations.
  • Draw logical conclusions.

Although human behaviour changes over time, Social Science studies it using scientific methods.

What Does Social Science Study?

Social Science studies almost every aspect of human life.

It includes

1. Human Society

  • Families
  • Communities
  • Villages
  • Cities
  • Nations

2. Human Behaviour

  • People's actions
  • Decision making
  • Beliefs
  • Traditions
  • Values

3. Government

  • Democracy
  • Constitution
  • Elections
  • Laws
  • Rights and Duties

4. Economy

  • Production
  • Distribution
  • Consumption
  • Markets
  • Money
  • Employment

5. Environment

  • Land
  • Climate
  • Water
  • Natural Resources
  • Human-environment interaction

6. History

  • Ancient Civilisations
  • Important Events
  • Kingdoms
  • Freedom Movements
  • Social Change

Nature of Social Science

Social Science has several important characteristics.

1. It studies human society.

It explains how people live together and organise their lives.

2. It is evidence-based.

Conclusions are based on facts, historical sources, maps, surveys, statistics and observations.

3. It is interdisciplinary.

It combines Geography, History, Political Science and Economics to understand society completely.

4. It studies change.

Society keeps changing due to technology, population growth, climate, economy and politics.

5. It develops critical thinking.

Students learn to question, analyse and understand problems instead of memorising facts.

Objectives of Social Science

The main objectives are to

  • Understand society.
  • Learn from history.
  • Respect different cultures.
  • Protect the environment.
  • Become responsible citizens.
  • Develop logical thinking.
  • Solve social problems.
  • Make informed decisions.

Difference Between Natural Science and Social Science

Natural Science

Social Science

Studies nature

Studies society

Studies plants, animals and physical objects

Studies people and human behaviour

Examples: Physics, Chemistry, Biology

Examples: Geography, History, Political Science, Economics

Mostly deals with natural laws

Deals with human behaviour and society

Experiments are common

Surveys, observations and historical evidence are commonly used

Importance of Social Science

Social Science is important because it helps us

  • understand our society,
  • know our rights and responsibilities,
  • respect diversity,
  • understand different cultures,
  • protect natural resources,
  • appreciate democracy,
  • make better decisions,
  • solve community problems,
  • become responsible citizens.

Without Social Science, it would be difficult to understand why societies develop differently or how governments, economies and cultures influence our daily lives.

Real-Life Examples

Example 1

Heavy rainfall causes floods.

A Social Scientist studies

  • why floods occur,
  • how people are affected,
  • government relief measures,
  • economic losses,
  • environmental impact.

Example 2

Food prices suddenly increase.

Social Science explains

  • demand and supply,
  • inflation,
  • transport costs,
  • government policies,
  • effect on families.

Example 3

People vote during elections.

Social Science helps us understand

  • why elections are held,
  • how governments are formed,
  • citizens' rights,
  • democratic participation.

Key Terms

Term

Meaning

Society

A group of people living together with shared customs and institutions.

Culture

The beliefs, traditions, language and way of life of people.

Institution

An organised system such as family, school or government.

Economy

The system of producing, distributing and consuming goods and services.

Government

The authority that governs a country and makes laws.

Citizen

A legal member of a country with rights and responsibilities.

Quick Concept Map

               SOCIAL SCIENCE

                     │

 ┌───────────────────┼───────────────────┐

 │                   │                   │

 Society         Human Behaviour     Environment

 │                   │                   │

 History        Political Science   Geography

                     │

                 Economics

                     │

          Better Understanding of Society

Important Points to Remember

✅ Social Science studies human society.

✅ It is based on evidence and logical reasoning.

✅ It combines Geography, History, Political Science and Economics.

✅ It helps us understand the past, present and future.

✅ It develops critical thinking and responsible citizenship.

Exam-Oriented Questions

Very Short Answer

Q1. What is Social Science?

Answer: Social Science is the systematic study of human society, behaviour, institutions and the interaction between people and their environment.

Q2. Why is Social Science called a science?

Answer: Because it studies society through observation, evidence, analysis and logical reasoning.

Short Answer (2–3 Marks)

Explain two objectives of Social Science.

Answer:

  1. To understand human society and its development.
  2. To develop responsible and informed citizens capable of solving social problems.

Long Answer (5 Marks)

Explain the importance of Social Science in our daily life.


  

Class 11 Geography Chapter 9 Notes: Solar Radiation, Heat Balance and Temperature (NCERT)

 

🔷 1. Insolation

Meaning:
The energy received by the Earth from the Sun is called Insolation.
It reaches the Earth in the form of electromagnetic waves, which include visible light, ultraviolet (UV), and infrared (IR) rays.

Importance:

  • Insolation controls the climate, temperature, and weather of the Earth.

  • Without solar energy, life and weather systems could not exist.

🔷 2. Solar Constant

  • The average amount of solar energy received on a unit area at the top of the atmosphere, when the Earth is at its mean distance from the Sun.

  • Its value is about 2 calories per cm² per minute.

  • It represents the constant rate at which solar energy reaches the Earth’s outer atmosphere.

🔷 3. Factors Affecting Insolation

  1. ☀️ Angle of the Sun’s Rays:

    • When the Sun is overhead, the rays are vertical → more heating.

    • When the Sun is slanting, the rays spread over a larger area → less heating.

  2. ⏰ Duration of the Day:

    • Longer days → more insolation.

    • Shorter days → less insolation.

  3. 🏔 Altitude:

    • Temperature decreases with height (about 1°C for every 165 m rise).

  4. 🌫 Cloud Cover:

    • Clouds reflect and absorb sunlight, reducing the amount reaching the surface.

  5. 🌍 Nature of the Surface:

    • Dark surfaces absorb more heat, while light-colored surfaces reflect more.

🔷 4. Earth’s Energy Balance

The Earth’s Heat Balance refers to the balance between the incoming solar radiation and the outgoing terrestrial radiation.

Energy Distribution:

Process

Approx. %

Description

Incoming solar radiation

100

Total solar energy from the Sun

Reflected by atmosphere and clouds

35

Sent back into space

Absorbed by atmosphere

14

Gases & clouds absorb energy

Absorbed by Earth’s surface

51

Land and water absorb heat

📊 Result:
Incoming energy = Outgoing energy → Earth’s average temperature remains stable 🌏

🔷 5. Heating and Cooling of the Atmosphere

The atmosphere is not directly heated by the Sun.
It is mainly heated by the Earth’s surface, which absorbs solar energy and then re-emits it as heat.

Modes of Heat Transfer:

  1. 🔥 Conduction:

    • Transfer of heat from the Earth’s warm surface to the lower layers of air.

  2. 🌡 Convection:

    • Warm air rises, cool air sinks — creating vertical movement of heat.

  3. 💨 Advection:

    • Horizontal transfer of heat through wind (e.g., warm or cold air movement).

  4. ☀️ Radiation:

    • The Earth re-radiates absorbed energy as long-wave infrared radiation.

🔷 6. Terrestrial Radiation

  • The Earth absorbs short-wave solar energy and emits long-wave infrared radiation back to the atmosphere.

  • This outgoing energy helps maintain the Earth’s temperature balance.

🌿 Greenhouse Effect:

  • Certain gases like CO₂, CH₄, O₃, and water vapour trap the outgoing heat and prevent it from escaping into space.

  • This natural process keeps the Earth’s average temperature around 15°C.

  • Without greenhouse gases, the temperature would drop to about −18°C.

✅ Note: The Greenhouse Effect is essential for maintaining life on Earth.

🔷 7. Heat Budget of the Earth

Definition:
The heat budget is the balance between the total incoming solar radiation and the total outgoing terrestrial radiation.

Process

Energy (Units)

Total incoming solar radiation

100

Reflected by clouds and atmosphere

35

Absorbed by atmosphere

14

Absorbed by Earth’s surface

51

Outgoing long-wave radiation

65

✅ Conclusion:
The Earth emits as much energy as it receives → maintaining a heat equilibrium.

🔷 8. Temperature

  • Temperature refers to the degree of hotness or coldness of a body or place.

  • It is measured with a thermometer.

  • Common units: Celsius (°C), Fahrenheit (°F), and Kelvin (K).

🔷 9. Factors Controlling Temperature

  1. 🌐 Latitude:

    • Temperature decreases from the equator to the poles.

  2. 🏔 Altitude:

    • Higher altitudes have lower temperatures.

  3. 🌊 Distance from the Sea:

    • Coastal areas have moderate temperatures.

    • Interior areas experience greater variations (continental effect).

  4. 🌊 Ocean Currents:

    • Warm currents raise temperatures of coastal regions.

    • Cold currents lower temperatures.

  5. ☁️ Cloud Cover:

    • Clouds reduce solar heating during the day and trap heat at night.

  6. 🌍 Nature of Surface:

    • Land heats and cools faster than water, affecting local temperature patterns.

🔷 10. Temperature Inversion

Normally, temperature decreases with height.
But sometimes, the reverse happens — temperature increases with height.
This condition is called Temperature Inversion.

Causes:

  1. Clear, calm, and cold nights 🌌

  2. Cold air trapped below warm air 🌫

  3. Valley regions where cold air settles at the bottom 🏞

📍 Result:
Lower layers become colder than upper layers → frost and fog often occur.

🔷 11. Distribution of Temperature

Temperature is unevenly distributed across the Earth due to various physical and geographical factors.

Isotherms:

  • Lines on a map joining places with the same temperature.

Global Patterns:

  • Equatorial region → hottest

  • Polar regions → coldest

  • Northern Hemisphere → higher temperature variation (more land)

  • Southern Hemisphere → moderate variation (more ocean)

📘 Summary Table

Concept

Explanation

Insolation

Solar energy received by Earth

Solar Constant

2 cal/cm²/min

Heat Balance

Equality between incoming & outgoing energy

Greenhouse Effect

Heat trapped by CO₂, CH₄, H₂O vapour

Temperature Factors

Latitude, Altitude, Sea, Currents, Clouds

Temperature Inversion

Increase in temperature with height


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