Download in PDF – NCERT Solutions for Class 8 Science based on latest CBSE Syllabus 2020 – 2021 – Free. Each chapter is solved and kept in a separate downloadable PDF file, so that students can use it offline also. Solutions contains pictures, MCQ answers, short and long answers questions and matching of column.
NCERT Solutions For Class 8 Science
The following NCERT solutions for class 8 Science contains NCERT chapter (both exemplar and NCERT book), solutions and the important points of the chapters.
Chapter 1: Crop production and management
Crop production and management – Agricultural practices (Cultivation of crops involves several activities undertaken by farmers over a period of time like preparation of soil, sowing, adding manure and fertilisers, irrigation, protecting from weeds, harvesting and storage), crop (when plants of the same kind are grown and cultivated at one place on a large scale, it is called a crop like kharif crops and rabi crops) and animal husbandry (obtaining food from animals on farming scale).
Chapter 2: Microorganisms: Friend and Foe
Organisms which can’t be seen by eyes alone are called microorganisms or microbes. Four major groups of microbes are bacteria, fungi, protozoa and algae. Viruses are also microscopic however, they reproduce only inside the cells of the host organism.
Chapter 3: Synthetic Fibres and Plastics
The synthetic fibres and plastics are made by man (not natural), so it is called synthetic or man-made fibres. A synthetic fibre is a chain of small units (chemical substances) joined together. Many such small units combine to form a large single unit called a polymer. Poly means many and mer means part/unit.
Chapter 4: Materials: Metals and Non-Metals
Metals and non-metals can be distinguished from each other on the basis of physical (malleability, ductility, shining, sonorous, good conductor of heat and electricity, etc.) and chemical properties (gives ions – cation/anions, reaction with water, with air, etc.).
Chapter 5: Coal and Petroleum
Wildlife, minerals, natural gas, coal and petroleum, etc. are exhaustible natural resources. As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonisation. Coke is the almost pure form of carbon. Petroleum was formed when the organism, living in the sea, died and settled at the bottom of the sea. Over millions of years, absence of air, high temperature and pressure transformed the dead organisms into petroleum and natural gas.
Chapter 6: Combustion and Flame
A chemical process in which a substance reacts with oxygen to give off heat is called combustion and the substance undergoes combustion is called combustible or fuel. The lowest temperature at which a substance catches fire is called it ignition temperature. Types of combustion – rapid combustion and spontaneous combustion.
Chapter 7: Conservation of Plants and Animals
The conservation of plants and animals is necessary as they are essential for the well being and survival of mankind. We should protect the endemic and endangered species. The record of endangered species is given in RED DATA BOOK. We should save trees, energy and water by reduce, recycle and reuse (RRR).
Chapter 8: Cell – Structure and Functions
Cell is the basic structural unit of an organ. Just like bricks in building, the cells in the living organisms, are basic structural units. It is first observed by Robert Hooke in 1665 under a simple magnifying device. A human body has trillions (thousand billion) of cells of different shape and size. The smallest cell is 0.1 to 0.5 micrometre in bacteria and the largest cell is 170 mm x 130 mm in egg of an ostrich.
Chapter 9: Reproduction in Animals
Reproduction in animals as well as in all living being is essential for the continuation of a species. Mode of reproduction – Sexual reproduction – This type of reproduction beginning from the fusion of male and female gametes. Asexual reproduction – This type of reproduction in which only a single parent is involved.
Chapter 10: Reaching the Age of Adolescence
The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence. The human body undergoes several changes during adolescence. These changes mark the onset of puberty. Increase in height, change in body shape, change in voice, development of sex organs, increase in activity of sweet and sebaceous glands, etc., are the changes at puberty.
Chapter 11: Force and Pressure
A push or a pull on an object is called a force. If the forces acting in opposite direction, the net force acting on the object is difference between the two forces. Force can change the state of motion or shape. Contact forces – Muscular forces and friction force. Non-contact forces – Magnetic force, electrostatic force and gravitational force.
Chapter 12: Friction
Force of friction act between the surfaces of two objects. Friction is caused by the irregularity on the two surfaces in contact. Even those surfaces which appear very smooth have a large number of minute irregularities on them. The substances which reduce friction force are called lubricants. When one body rolls over the surface of another body, the resistance to its motion is called the rolling friction.
Chapter 13: Sound
Sound plays an important role in our life. It helps us to communicate with one another. The to and fro or back and forth motion of an object is called vibration. In humans, the sound is produced by the voice box or the larynx which is at the upper end of the windpipe. Sound needs a medium for propagation it can’t travel in vacuum.
Chapter 14: Chemical Effect of Electric Current
Under the certain conditions most of the materials conduct electricity. According to that it is classified as good conductors or poor conductors. The passage of an electric current through a conducting solutions causes chemical reactions is known as chemical effect of electric current. Electroplating is one of its example.
Chapter 15: Some Natural Phenomena
Wind, storms, cyclones, lightning are some natural phenomena. Lightning is caused by the accumulation of charges in the clouds. Types of charges – positive and negative. Same charges repel each other and opposite charges attract each other. Electroscope is used to detect whether a body is having charge or not. Earthquake is another natural phenomena which can cause large scale destruction of human life and property.
Chapter 16: Light
Light makes the things visible to our eyes. It follows the laws of reflection – incident angle = reflected angle. When all the parallel rays reflected from a plane surface are not parallel, the reflection is called diffused or irregular. On the other hand reflection from a smooth surface like that of a mirror is called regular reflection.
Chapter 17: Stars and the Solar System
The stars, the planets, the moon and many other objects in the sky are called celestial objects. The various shapes of the bright part of the moon as seen during a month are called phases of moon. Moon’s surface is dusty and barren, there are many craters of different sizes. It has a large number of steep and high mountains. The stars forming a group that has a recognisable shape is called a constellation.
Chapter 18: Pollution of Air and Water
In the atmosphere, by volume about 78% of Nitrogen and 21% of oxygen. Carbon dioxide, argon, methane, ozone and water vapour are also present in very small quantities. When this composition is disturbed and air is contaminated by unwanted substance which have a harmful effect on both the living and non-living, it is referred to as air pollution.