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Class 9th Science NCERT Exemplar Solutions
1. Matter In Our Surroundings
This chapter explores the nature of **matter**, defining it as anything with mass that occupies space. It delves into the characteristic properties of particles of matter and the different states: solid, liquid, and gas. The chapter explains the effect of temperature and pressure on these states and discusses physical processes like melting, boiling, evaporation, condensation, and sublimation based on particle behaviour. Understanding matter's states and transformations is fundamental to chemistry and helps explain everyday phenomena.
2. Is Matter Around Us Pure?
This chapter differentiates between **pure substances** (elements and compounds) and **mixtures**. Mixtures are classified as homogeneous (uniform composition) and heterogeneous (non-uniform composition). Various physical methods for separating the components of different types of mixtures are explained, such as evaporation, filtration, distillation, chromatography, and crystallisation. Concepts like solutions, suspensions, and colloidal solutions, their properties (e.g., Tyndall effect), and how to distinguish between them are also covered, essential for analyzing and purifying substances.
3. Atoms And Molecules
This fundamental chemistry chapter introduces the basic building blocks of matter: **atoms** and **molecules**. It discusses the **Laws of Chemical Combination** (Conservation of Mass, Constant Proportions). **Dalton's Atomic Theory** is presented as an early model. The concepts of atomic mass, molecular mass, and the **mole concept** ($\textsf{1 mole} = 6.022 \times 10^{23}$ particles), Avogadro's constant, and molar mass are introduced. These concepts are crucial for performing calculations related to chemical reactions and understanding the quantitative aspects of chemistry.
4. Structure Of The Atom
This chapter explores the intricate internal structure of the atom, revealing it is not indivisible. It discusses the discoveries of **subatomic particles** (electrons, protons, neutrons) and the evolution of atomic models, including Thomson's plum pudding model, Rutherford's nuclear model based on alpha scattering experiments, and Bohr's model for the hydrogen atom, explaining electron shells and energy levels. Concepts like atomic number (Z), mass number (A), isotopes (same element, different neutrons), and isobars (different elements, same mass number) are explained, providing a foundational understanding of atomic composition.
5. The Fundamental Unit Of Life
This chapter establishes the **cell** as the basic structural and functional unit of all living organisms. It covers the history of cell discovery and the key postulates of the **Cell Theory**. The structure of both **plant cells** and **animal cells** is discussed, highlighting their differences and similarities. Various **cell organelles** within the cytoplasm, such as the cell membrane, cell wall (in plants), nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, mitochondria, and plastids (chloroplasts in plants), are described with their respective functions, illustrating the complexity and organization within a single cell.
6. Tissues
In multicellular organisms, similar cells group together to form **tissues** that perform specific functions, enabling efficiency and division of labour. This chapter explores different types of tissues in both plants and animals. **Plant tissues** are classified into meristematic and permanent tissues (simple: parenchyma, collenchyma, sclerenchyma; complex: xylem and phloem). **Animal tissues** are categorized into epithelial, connective (including blood and bone), muscular, and nervous tissues. Understanding tissue organization helps explain how organs and organ systems are formed and function in complex organisms.
7. Diversity In Living Organisms
This chapter explores the enormous variety of life forms on Earth (**biodiversity**) and the need for their systematic classification. It discusses the basis of classification and the hierarchical system used (species, genus, family, order, class, phylum/division, kingdom). The **Five-Kingdom classification** (Monera, Protista, Fungi, Plantae, Animalia) proposed by Whittaker is introduced, and the salient features of major groups within the Plant Kingdom and Animal Kingdom are briefly discussed. This classification helps in studying and understanding the relationships and evolutionary history among different organisms, simplifying the study of life's vast diversity.
8. Motion
This physics chapter introduces the concept of **motion** and how to describe it. It defines key terms like distance, displacement (a vector quantity), speed, velocity (a vector quantity), and acceleration (the rate of change of velocity). Different types of motion, such as uniform and non-uniform motion, are discussed. The chapter utilizes **graphs** (distance-time and velocity-time) to represent and analyze motion. The fundamental **equations of motion** ($\textsf{v = u + at}$, $\textsf{s = ut} + \frac{1}{2}\textsf{at}^2$, $\textsf{v}^2 - \textsf{u}^2 = 2\textsf{as}$) for uniformly accelerated linear motion are derived and applied to solve problems.
9. Force And Laws Of Motion
This chapter investigates the cause of motion: **force**, defined as a push or pull. It explains how force can change an object's state of motion or shape. **Newton's Laws of Motion** are central: the First Law describes **inertia**, the Second Law relates force, mass, and acceleration ($\textsf{F = ma}$), and the Third Law states that for every action, there is an equal and opposite reaction. The concept of **momentum** ($\textsf{p = mv}$) and the **Conservation of Linear Momentum** principle are derived and applied to analyse interactions like collisions, providing a fundamental framework for understanding mechanics.
10. Gravitation
This chapter explores the universal attractive force between any two objects with mass: **gravitation**. **Newton's Law of Universal Gravitation** ($\textsf{F} = \textsf{G}\frac{\textsf{m}_1\textsf{m}_2}{\textsf{r}^2}$) is discussed. Concepts like free fall, **acceleration due to gravity** ($\textsf{g}$), and the distinction between mass and weight are explained. The chapter also introduces **thrust** and **pressure** (force per unit area), the **buoyant force** exerted by fluids, and **Archimedes' principle** explaining why objects float or sink. These principles are applied to understand phenomena ranging from falling objects to the motion of planets and the behaviour of objects in fluids.
11. Work And Energy
This chapter introduces the physics concepts of **work**, **energy**, and **power**. **Work** is done when a force causes displacement in the direction of the force ($\textsf{W} = \textsf{F} \cdot \textsf{s}$). **Energy** is defined as the capacity to do work, discussed in various forms, focusing on mechanical energy, which includes **kinetic energy** ($\textsf{KE} = \frac{1}{2}\textsf{mv}^2$) due to motion and **potential energy** due to position or state. The **Work-Energy Theorem** and the fundamental **Law of Conservation of Energy** (energy cannot be created or destroyed, only transformed) are key. **Power** is defined as the rate at which work is done ($\textsf{P} = \frac{\textsf{W}}{\textsf{t}}$).
12. Sound
This chapter explores **sound**, a form of energy produced by **vibrations**. It explains how sound is produced and requires a material medium (solid, liquid, or gas) to travel, demonstrating that it cannot propagate in a vacuum. Key characteristics of sound waves, such as amplitude (related to loudness), frequency (related to pitch), time period, and speed (varying in different media), are discussed. The chapter covers reflection of sound (echoes), absorption, and the range of human hearing, also touching upon the distinction between musical sound and noise.
13. Why Do We Fall Ill?
This chapter discusses the concepts of **health** and **disease**, defining health as a state of physical, mental, and social well-being. It explores the causes of diseases, differentiating between immediate and contributory causes. Diseases are broadly classified into **infectious diseases** (caused by pathogens like bacteria, viruses, fungi, protozoans) and **non-infectious diseases** (e.g., genetic, lifestyle-related). Modes of disease transmission, principles of prevention (including public hygiene and vaccination), and basic principles of treatment are discussed, highlighting the importance of community health and individual lifestyle choices for preventing illness.
14. Natural Resources
This chapter highlights the essential **natural resources** available on Earth, such as air, water, and soil, which are crucial for the sustenance of life. It discusses the composition and importance of these resources. The dynamic nature of the environment is explained through **biogeochemical cycles**, such as the water cycle, carbon cycle, oxygen cycle, and nitrogen cycle, illustrating how elements circulate through the living and non-living components of the environment. The chapter also addresses environmental problems like pollution and the need for sustainable use and management of these resources.
15. Improvement In Food Resources
This chapter focuses on strategies to enhance the production and quality of **food resources** to meet the demands of a growing population, particularly relevant in India. It discusses methods for improving **crop production**, including crop variety improvement (e.g., hybridisation), crop production management (nutrient management, irrigation, cropping patterns), and crop protection management (from pests and diseases). **Animal husbandry**, covering the scientific management of farm animals for food (cattle for milk, poultry for eggs/meat, fish farming, beekeeping), is also explored to enhance livestock production.
Sample Paper I
This Sample Paper is the 1st Sample Paper provided in Exemplar designed to help students practice and assess their understanding of the Class 9th Science syllabus covered in the NCERT Exemplar Solutions. It contains a variety of practice questions based on the concepts and topics from the preceding chapters (1-15). Working through this sample paper allows students to familiarize themselves with the examination pattern, question types, and time management, enabling effective revision and preparation for their assessments on science topics.
Sample Paper II
This second Sample Paper is a part of the Class 9th Science NCERT Exemplar Solutions. Like Sample Paper I, it offers a collection of practice questions covering the breadth and depth of the science syllabus (Chapters 1-15). Utilising this resource allows students further opportunity to consolidate their learning, test their knowledge application, and build confidence before examinations. Engaging with multiple sample papers helps students reinforce concepts and improve problem-solving skills acquired from the chapters.