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Class 8th Science MCQ Questions
1. Crop Production And Management
This chapter focuses on the agricultural practices essential for producing food crops, vital for India's large population. It covers key steps such as preparing the soil, sowing seeds, adding manure and fertilisers for nutrients, providing water through irrigation, protecting crops from weeds and pests, harvesting the mature crop, and proper storage of grains to minimize spoilage. Understanding these practices is crucial for increasing food production and ensuring food security across the country.
2. Microorganisms : Friend And Foe
Microorganisms are tiny living beings found everywhere, with both beneficial and harmful roles. This chapter explores various types like bacteria, fungi, protozoa, and viruses. It discusses their friendly aspects, such as in making curd and bread, producing antibiotics and vaccines, and decomposing waste. It also highlights their role as foes, causing diseases in humans, plants, and animals (like typhoid or malaria). Methods to prevent common microbial diseases and food spoilage are also covered.
3. Synthetic Fibres And Plastics
This chapter introduces **synthetic fibres** (man-made) like nylon, rayon, and polyester, discussing their properties (strength, durability) and uses in clothing and other items. It also explores **plastics**, their types (thermoplastics, thermosetting), and properties (lightweight, non-reactive), which make them widely used. However, the chapter emphasizes the environmental problems caused by plastics due to their **non-biodegradable** nature and the need for responsible use, recycling, and proper disposal to minimize pollution.
4. Materials : Metals And Non-Metals
This chapter classifies materials into **metals** and **non-metals** based on their distinct physical and chemical properties. Physical properties include lustre, hardness, malleability (can be hammered), ductility (can be drawn into wires), conductivity of heat and electricity, and state at room temperature. Chemical properties cover their reactions with oxygen, water, acids, and bases. The chapter also introduces the **Reactivity Series** of metals, explaining how more reactive metals displace less reactive ones, and highlights the diverse uses of these materials in daily life and industry.
5. Coal And Petroleum
**Coal** and **petroleum** are major **fossil fuels**, non-renewable sources of energy formed over millions of years from ancient organic matter. This chapter explains their formation, extraction, and the various products obtained from their processing (like petrol, diesel, kerosene, LPG, coke, coal tar). These fuels are critical for industries and transport globally and in India. The chapter emphasizes that these resources are **finite** and need conservation, stressing the importance of exploring alternative energy sources due to their limited availability and environmental impact.
6. Combustion And Flame
This chapter focuses on **combustion**, the rapid reaction between a substance and oxygen that produces heat and light, commonly known as burning. It identifies **combustible substances** and the three necessary conditions for combustion: fuel, oxygen, and reaching the ignition temperature. Different types of combustion (rapid, spontaneous, explosion) are discussed. The structure of a **flame**, seen when gaseous substances burn, is explained with its different zones. The chapter also covers methods for controlling fire by removing one or more of these essential conditions.
7. Conservation Of Plants And Animals
This chapter emphasizes the importance of preserving **biodiversity** and natural habitats. It discusses the causes and consequences of **deforestation**, such as soil erosion and climate change. Concepts like **endangered species**, extinct species, flora, fauna, and endemic species are introduced. Different methods of **conservation** are explained, including the establishment of **national parks**, **wildlife sanctuaries**, and **biosphere reserves** in India to protect forests and wildlife, highlighting the need for collective effort in preserving our natural heritage for ecological balance and future generations.
8. Cell — Structure And Functions
This chapter introduces the **cell** as the basic structural and functional unit of all living organisms. It explains the discovery of the cell and discusses the diversity in cell number, shape, and size. The fundamental components of a cell, including the **cell membrane**, **cell wall** (in plant cells), **cytoplasm**, and **nucleus**, are described. Various **cell organelles** located within the cytoplasm, such as vacuoles, plastids (chloroplasts), and mitochondria, are introduced with their basic functions, providing a microscopic view of life and highlighting the differences between plant and animal cells.
9. Reproduction In Animals
This chapter explains how animals produce new individuals to ensure the continuation of their species. It covers both **asexual reproduction**, involving a single parent (e.g., binary fission in Amoeba, budding in Hydra), and **sexual reproduction**, which involves the fusion of male and female gametes (**fertilisation**). The chapter details both internal (inside the body) and external (outside the body) fertilisation. The development of the embryo and different life cycles in animals, including **metamorphosis** in organisms like frogs and silkworms, are also discussed, illustrating the varied reproductive strategies in the animal kingdom.
10. Reaching The Age Of Adolescence
**Adolescence** is the transitional period between childhood and adulthood, marked by the onset of **puberty** and rapid physical, emotional, and psychological changes. This chapter discusses the changes associated with puberty, including growth spurts, changes in body shape and voice, increased activity of sweat and sebaceous glands, and the development of secondary sexual characteristics, driven by hormones. The chapter also highlights the importance of personal hygiene, proper nutrition, and understanding reproductive health during this crucial stage of development, providing essential information for teenagers navigating these changes.
11. Force And Pressure
This chapter introduces the concepts of **force** and **pressure**. A force is defined as a push or pull that can change an object's state of motion (at rest or in motion) or change its shape. Different types of forces, both contact (e.g., muscular, friction) and non-contact (e.g., magnetic, electrostatic, gravitational), are discussed. **Pressure** is defined as the force acting per unit area ($\textsf{Pressure} = \frac{\textsf{Force}}{\textsf{Area}}$), explaining that it depends on both the magnitude of the force and the area over which it is applied. Pressure exerted by liquids and gases is also covered, illustrating its presence and effects in everyday situations.
12. Friction
**Friction** is a force that opposes the relative motion between two surfaces in contact. This chapter explains the cause of friction (interlocking of surface irregularities) and discusses different types: static friction (opposing motion initiation), sliding friction (opposing sliding), and rolling friction (opposing rolling), noting that rolling friction is generally less than sliding friction. The chapter explores situations where friction is beneficial (e.g., walking, braking) and where it is undesirable (e.g., wear and tear), and discusses methods to increase or decrease friction, such as using lubricants or changing the surface.
13. Sound
**Sound** is a form of energy that is produced by **vibrations**. This chapter explains how sound is produced and requires a material medium (solid, liquid, or gas) to travel, demonstrating that it cannot propagate through a vacuum. Key characteristics of sound waves, such as amplitude (related to loudness), frequency (related to pitch), time period, and speed, are discussed. The chapter differentiates between musical sound and noise, highlights the harmful effects of **noise pollution**, and suggests measures to control it, emphasizing the physical nature of sound and its impact.
14. Chemical Effects Of Electric Current
This chapter explores the **chemical changes** that can occur when electric current passes through certain liquids known as electrolytes. It introduces the process of **electrolysis**, where electricity is used to decompose a substance. Experiments demonstrating the conduction of electricity through various liquids and the resulting chemical effects (e.g., deposition of metal) are discussed. The chapter highlights practical applications of these effects, such as **electroplating**, a process used to coat a metal object with a thin layer of another metal for protection or decoration, common in jewellery, automotive parts, and utensils.
15. Some Natural Phenomena
This chapter focuses on understanding two powerful and sometimes destructive **natural phenomena**: **lightning** and **earthquakes**. It explains how **lightning** is caused by the accumulation and discharge of electric charges in storm clouds and between clouds and the ground, discussing necessary safety measures during thunderstorms. **Earthquakes** are described as sudden vibrations in the Earth's crust caused by the movement of tectonic plates. The chapter covers their causes and effects and discusses safety precautions to take during an earthquake, raising awareness about these natural hazards.
16. Light
This chapter delves into the properties of **light** and how we perceive the world visually. It reinforces that light travels in straight lines. The phenomenon of **reflection**, the bouncing back of light from surfaces like mirrors, is explained, including the laws of reflection and image formation by **plane mirrors**. The chapter also introduces image formation by **spherical mirrors** (concave and convex) using ray diagrams. The structure and working of the **human eye**, common eye defects and their correction, and the importance of eye donation are also covered, highlighting the role of light and vision.
17. Stars And The Solar System
This chapter takes you on an astronomical journey, exploring celestial objects beyond Earth. It introduces **stars**, their vast distances, and **constellations** (patterns of stars). The **Solar System**, consisting of the Sun, eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune), asteroids, comets, and meteoroids, is described. The Moon, its phases, and artificial satellites are also covered. The chapter provides a basic understanding of our place in the universe and the movements of celestial bodies, sparking curiosity about astronomy and space.
18. Pollution Of Air And Water
This chapter addresses the critical environmental issue of **pollution**, focusing on **air** and **water** pollution. It identifies the major sources and types of **air pollutants** (e.g., smoke, dust, harmful gases from vehicles and industries) and their adverse effects on human health, plants, and the environment (e.g., acid rain). Similarly, it discusses the sources and types of **water pollutants** (e.g., sewage, industrial waste, agricultural chemicals) and their consequences for aquatic life and human health. The chapter stresses the need for measures to prevent and control air and water pollution for a healthier environment, a significant challenge in India.