| Science NCERT Exemplar Solutions (Class 6th to 10th) | ||||||||||||||
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| Science NCERT Exemplar Solutions (Class 11th) | ||||||||||||||
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| Science NCERT Exemplar Solutions (Class 12th) | ||||||||||||||
| Physics | Chemistry | Biology | ||||||||||||
Class 7th Science NCERT Exemplar Solutions
1. Nutrition In Plants
This chapter explains how plants obtain the nutrients they need to survive. It focuses primarily on **photosynthesis**, the process by which green plants, acting as **autotrophs**, synthesize their own food using carbon dioxide ($\textsf{CO}_2$), water, sunlight, and chlorophyll. The chapter also introduces **heterotrophic nutrition** in some plants, such as parasitic plants (like Cuscuta) that derive nourishment from others and insectivorous plants that trap insects. Understanding plant nutrition is fundamental to appreciating their role as producers in ecosystems.
2. Nutrition In Animals
This chapter explores how animals, being **heterotrophs**, obtain and process food. It describes the different steps involved in animal nutrition: **ingestion** (taking in food), **digestion** (breaking down complex food), **absorption** (taking digested food into body), **assimilation** (using absorbed food), and **egestion** (removing waste). The chapter provides a detailed overview of the **human digestive system**, explaining the function of each organ from mouth to anus. Digestion in other animals like grass-eating ruminants and the simple process in Amoeba are also discussed.
3. Fibre To Fabric
Building on the concept of fibres, this chapter specifically focuses on two important **animal fibres**: **wool** and **silk**. It describes the animals from which wool is obtained (sheep, goat, yak) and the process of converting fleece into woollen yarn and fabric, including shearing, scouring, sorting, and spinning. The life cycle of the **silk moth** and the process of obtaining silk fibre from cocoons through **sericulture** are explained. This chapter provides insight into the production of these valuable natural textiles.
4. Heat
This chapter differentiates between **heat** (a form of energy) and **temperature** (a measure of hotness or coldness). It explains that heat flows from a region of higher temperature to lower temperature. Different temperature scales like Celsius and Fahrenheit are introduced, along with the use of **thermometers** (clinical and laboratory) for measurement. The three modes of heat transfer – **conduction** (in solids), **convection** (in liquids and gases), and **radiation** (transfer without medium) – are explained with examples from daily life, such as cooking and feeling warmth from the sun.
5. Acids, Bases And Salts
This chapter introduces three important categories of chemical substances: **acids**, **bases**, and **salts**. Acids are typically sour (e.g., lemon juice), and bases are bitter and soapy (e.g., baking soda solution). **Indicators** like litmus paper (turning red in acid, blue in base), turmeric, and china rose extract are used to test whether a substance is acidic or basic. The reaction between an acid and a base, called **neutralisation**, which produces a salt and water, is explained. Examples of these substances found in nature and home are provided.
6. Physical And Chemical Changes
This chapter helps differentiate between two types of changes observed in substances around us. **Physical changes** alter the physical properties (shape, size, state) but not the chemical composition of the substance, and are often reversible (e.g., melting ice, cutting paper). **Chemical changes**, on the other hand, result in the formation of new substances with different chemical properties and are usually irreversible (e.g., burning wood, rusting of iron, cooking). Recognizing these differences helps in understanding transformations in matter.
7. Weather, Climate And Adaptations Of Animals To Climate
This chapter distinguishes between **weather** (day-to-day atmospheric conditions) and **climate** (long-term average weather pattern of a region). Factors influencing weather and climate are discussed. A significant part focuses on how animals develop specific features or behaviors called **adaptations** to survive in particular climatic conditions. Examples of adaptations in animals living in polar regions (like polar bears' fur) and tropical rainforests (like monkeys' tails for climbing) illustrate how organisms are suited to their environment, showcasing nature's resilience and diversity.
8. Winds, Storms And Cyclones
This chapter explores the movement and power of air. It explains that **wind** is caused by differences in air pressure, often due to uneven heating of the Earth's surface. The chapter discusses how small pressure differences create gentle breezes, while large differences can lead to strong winds, storms, and **cyclones**. The structure and devastating effects of cyclones are explained. Safety measures to be taken during storms and cyclones are highlighted, emphasizing preparedness and minimizing damage from these powerful natural phenomena, particularly relevant in India's coastal areas.
9. Soil
**Soil** is a vital natural resource that supports plant life. This chapter discusses its formation through the weathering of rocks and its composition, which includes mineral particles, organic matter (humus), water, air, and living organisms. Different types of soil (sandy, clayey, loamy) are described based on particle size and properties like water percolation rate. The chapter also addresses the problem of **soil erosion** (removal of topsoil) and methods for **soil conservation**, emphasizing the importance of protecting this non-renewable resource for agriculture and environmental health.
10. Respiration In Organisms
This chapter explains **respiration**, the process by which living organisms release energy from food. It differentiates between **aerobic respiration** (requiring oxygen) and **anaerobic respiration** (without oxygen). Respiration in various organisms is discussed: breathing and cellular respiration in humans, respiration through skin in earthworms, through tracheae in insects, and through gills in fish. Respiration in plants, involving exchange of gases through stomata in leaves and lenticels in stems, is also covered, highlighting the fundamental energy-releasing mechanism in all life forms.
11. Transportation In Animals And Plants
This chapter explores how essential substances are moved within living organisms. In **animals**, the circulatory system, consisting of blood, blood vessels, and the heart, transports nutrients, oxygen, hormones, and waste products. The structure and function of the human circulatory system and heart are explained. In **plants**, water and minerals are transported from roots upwards by **xylem**, while food synthesized in leaves is transported to other parts by **phloem**. The process of **transpiration**, water loss from leaves, also aids in water uptake.
12. Reproduction In Plants
This chapter explains how plants produce new individuals to perpetuate their species. It describes **asexual reproduction**, which involves a single parent and includes methods like vegetative propagation (using parts like stems, roots, leaves), budding, fragmentation, and spore formation. **Sexual reproduction** in plants, involving the fusion of male and female gametes typically within a flower, is also covered, detailing the processes of **pollination** and **fertilisation** leading to the formation of seeds and fruits. Understanding plant reproduction is vital for agriculture and maintaining plant populations.
13. Motion And Time
This chapter builds upon the concept of motion by introducing the measurement of time and the relationship between distance and time through **speed**. It defines **speed** as the distance covered per unit time ($\textsf{Speed} = \frac{\textsf{Distance}}{\textsf{Time}}$) and differentiates between uniform and non-uniform motion. Methods for measuring time using various devices are discussed. The chapter also introduces the use of **distance-time graphs** to represent motion and calculate speed, providing tools for analyzing and describing the movement of objects quantitatively.
14. Electric Current And Its Effects
This chapter explores the effects produced when **electric current** flows through a circuit. It revisits the components of an electric circuit and how to represent them using symbols in circuit diagrams. The chapter focuses on the **heating effect of electric current**, where electrical energy is converted into heat (e.g., in heaters, bulbs), and the **magnetic effect of electric current**, where a current-carrying wire produces a magnetic field (used in electromagnets). Safety precautions related to electricity are also emphasized.
15. Light
This chapter delves deeper into the properties of **light** and how it interacts with objects. It reinforces that light travels in straight lines. The phenomenon of **reflection**, the bouncing of light off surfaces, is explained, including the laws of reflection and image formation by **plane mirrors**. Image formation by **spherical mirrors** (concave and convex) and the appearance of objects in different coloured lights are also introduced. The chapter highlights how light enables us to see the world around us and forms the basis of optics.
16. Water: A Precious Resource
This chapter underscores the vital importance and increasing scarcity of **water**. It discusses various sources of fresh water, the different forms water exists in, and the continuous circulation of water through the **water cycle**. The uneven distribution of water resources globally and the causes of water scarcity are highlighted. Methods for **water conservation**, including rainwater harvesting and efficient irrigation techniques, are discussed. The chapter stresses the urgent need for responsible use and conservation of water for sustainable living, a critical issue in India.
17. Forests: Our Lifeline
Forests are vital ecosystems providing numerous benefits to humans and the environment. This chapter explores forests as dynamic entities, highlighting their role in maintaining ecological balance, preventing soil erosion, regulating the water cycle, and purifying the air. It discusses the diverse organisms living in forests and the concept of **food chains** and **food webs** illustrating interdependence. The chapter emphasizes the importance of conserving forests as a source of timber, medicines, and livelihoods, and as crucial habitats for biodiversity, considering their significance in India's natural heritage.
18. Wastewater Story
This chapter addresses the issue of **wastewater** generated from homes, industries, and other sources. It explains what wastewater is and the impurities it contains. The process of treating wastewater in a **sewage treatment plant (STP)** through physical, chemical, and biological processes to remove pollutants is described. The chapter emphasizes the importance of proper sanitation and wastewater management to prevent pollution of water bodies and protect public health and the environment, highlighting the need for effective waste disposal systems, especially in growing urban areas in India.