Extra Questions for Class 8 Science

Extra Questions for Class 8 Science CBSE Extra Questions for Class 8 Science Most students start looking for Extra questions as the exam nears. By this time they have finished the syllabus and started with the revision. The CBSE E ​ xtra Questions for Class 8 Science​ will help them. Here we have compiled the Extra Questions for all the chapters of CBSE class 8 science subject. Going through them students understand the types of questions asked in the exam. From basic to a high level, all types of questions are provided for students practice.

● ● ● ● ● ● ● ● ● ● ● ● ●

Crop Production and Management Class 8 Extra Questions Microorganisms: Friend and Foe Class 8 Extra Questions Synthetic Fibres and Plastics Class 8 Extra Questions Materials: Metals and Non-Metals Class 8 Extra Questions Coal and Petroleum Class 8 Extra Questions Combustion and Flame Class 8 Extra Questions Conservation of Plants and Animals Class 8 Extra Questions Cell Structure and Functions Class 8 Extra Questions Reproduction in Animals Class 8 Extra Questions Reaching the Age of Adolescence Class 8 Extra Questions Force and Pressure Class 8 Extra Questions Friction Class 8 Extra Questions Sound Class 8 Extra Questions

● ● ● ● ●

Chemical Effects of Electric Current Class 8 Extra Questions Some Natural Phenomena Class 8 Extra Questions Light Class 8 Extra Questions Stars and the Solar System Class 8 Extra Questions Pollution of Air and Water Class 8 Extra Questions

1. Crop Production and Management Class 8 Extra Questions CBSE Crop Production and Management Class 8 Extra Questions Same kinds of plants grown and cultivated at a place constitute a crop. In India, based on seasons crops can be broadly categorized into two types, rabi and Kharif crops. In order to provide adequate food to the growing population, we need to adopt certain agricultural practices.

Agricultural practices involve Preparation of soil, sowing of seeds, manuring, irrigation, weeding, crop harvesting, and storage. Soil is prepared by plowing (tilling) and leveling.

Plowing is done by the plow, cultivator, and hoe while leveling is done by leveler. Sowing is the process of planting seeds and plays a key role in crop production. B Before sowing, healthy and good quality seeds are selected. Please refer ​Crop Production and

Management Class 8 Extra Questions​ for more information.

2. Microorganisms: Friend and Foe Class 8 Extra Questions CBSE Notes for Microorganisms: Friend and Foe Class 8 Extra Questions Microorganisms are the living organisms, which are not visible through naked eyes.

Microorganisms are divided into four groups; bacteria, fungi, protozoa, and some algae.

Viruses are also microscopic microbes and they reproduce inside the host cell. The microorganism can survive in hot springs, on the ocean floor, high in the atmosphere and

deep inside rocks within the Earth's crust. They can also live inside the animal body as well as on the body of other microorganisms.

Some microorganisms play an important role in our daily life. They are used for various purposes such as preparation of curd, bread, and cake. The bacteria responsible for the formation of curd are Lactobacillus. Yeast converts sugar into alcohol by the process called fermentation. They are used to manufacture antibiotics, vaccines, etc. Some of the vaccines are DPT, polio vaccine, etc. Several diseases, including cholera, tuberculosis, smallpox, and hepatitis can be prevented by vaccination. Please refer M ​ icroorganisms: Friend and Foe

Class 8 Extra Questions​ for more information.

3. Synthetic Fibres and Plastics Class 8 Extra Questions CBSE Notes for Synthetic Fibres and Plastics Class 8 Extra Questions

● Fibre is a type of thread that is strong enough to make clothes, nets, wires, etc. It is obtained from natural and man-made sources. Natural fibers are obtained from plants and animals. Synthetic fibers are obtained from petrochemicals which are raw materials of petroleum origin. Synthetic fiber is a chain of small units called monomers. These monomers combine to form a large single unit called polymer.

Depending upon the chemicals used for preparing synthetic fibers the synthetic fibers are of different types. ● Plastics are the synthetic polymers that can be molded or set into any desired shape when soft and then hardened to make durable articles. Plastics can be formed by linear arrangement of monomers or by the cross-linked arrangement of monomers.

Thermoplastics and thermosetting are the two types of plastics. Thermoplastics get deformed easily on heating and can be bent into desired shapes on the heating again and again. Please refer ​Synthetic Fibres and Plastics Class 8 Extra Questions​ for more information.

4. Materials: Metals and Non-Metals Class 8 Extra Questions CBSE Notes for Materials: Metals and Non-Metals Class 8 Extra Questions

Chemical elements can be classified as metals and non-metals. Some metals, as well as non-metals, occur in a free state. Most of the metals are solid under normal conditions of temperature and pressure. The property of metals having a shining surface is called metallic luster. Metals also show the property of sonority. Metals show the property of malleability. Metals are ductile and good conductors of heat and electricity.

Metals are reactive towards oxygen, water, dilute acids and show displacement reaction.

Metals react with oxygen to give basic oxides. Metals react with water to produce metal hydroxides/ metal oxide and hydrogen gas. Metal oxides are basic in nature, so they turn red litmus blue. Please refer ​Materials: Metals and Non-Metals Class 8 Extra Questions for more information.

5. Coal and Petroleum Class 8 Extra Questions CBSE Coal and Petroleum Class 8 Extra Question​s Natural resources are the naturally occurring substances that are considered valuable in their relatively unmodified form. Natural resources are classified as exhaustible and inexhaustible. Exhaustible resources are present in limited quantity in nature. These are exhausted by human activities. Inexhaustible natural resources are not likely to be exhausted by human activities.

Fuel is a material that is burnt or changed in order to obtain energy. Fuels are classified as natural fuels and processed fuels. Some of the natural fuels are found as fossil fuels. Fossil fuels are formed by the decomposition of dead plants and animals b buried under Earth over millions of years ago. Please refer C ​ oal and Petroleum Class 8 Extra Questions​ for more information.

6. Combustion and Flame Class 8 Extra Questions CBSE Combustion and Flame Class 8 Extra Questions Combustion is the act of burning. Combustion is a chemical process in which a substance reacts with oxygen to produce heat and light. Combustion is of three types- rapid combustion, spontaneous combustion, and explosion. On the basis of combustion, substances are classified as combustible and non-combustible substances. Air, fuel and ignition temperature are essential for combustion. Ignition temperature is the minimum temperature at which a substance catches fire and starts burning.

Fire is the process of the oxidation of a combustible material by which heat and light are released and product such as carbon dioxide is formed. Water and carbon dioxide act as fire extinguishers as they stop the supply of air or brings down the temperature of the fuel.

When a substance vapourises during burning, a shiny light-producing heat is obtained. The shiny light is called flame. A flame has three zones- outer or non-luminous zone, middle or luminous zone, and innermost or dark zone. Please refer C ​ ombustion and Flame Class 8

Extra Questions​ for more information.

7. Conservation of Plants and Animals Class 8 Extra Questions CBSE Conservation of Plants and Animals Class 8 Extra Questions Conservation of plants and animals is required to maintain the balance in the ecosystem.

Still, people perform deforestation and hunt animals to fulfill their needs. Deforestation is done to procure land for cultivation, build houses and factories, use wood as fuel and furniture, etc.

Deforestation leads to global warming, an increase in pollution, uncertain rainfall pattern, floods, drought, soil erosion, lowering of the level of groundwater, desertification, etc.

Certain rules, methods, and policies are laid down by the government to protect and conserve forest and wildlife. The protected areas for conservation of plants and animals are biosphere reserves, wildlife sanctuaries, and the national parks, etc. Biosphere reserves are the areas meant for the conservation of biodiversity. Please refer ​Conservation of Plants

and Animals Class 8 Extra Questions​ for more information.

8. Cell Structure and Functions Class 8 Extra Questions CBSE Cell Structure and Functions Class 8 Extra Questions

● Cell is the structural and functional unit of all the living organisms, which is capable of carrying out all life processes. Robert Hooke observed honeycomb-like compartments under the microscope and named them ‘cells’. ● The protoplasm includes the cytoplasm and the nucleus. In eukaryotes, the nucleus is separated from the cytoplasm by a nuclear membrane and it directs all the life processes of the cell. Within the nucleus, the nucleolus is present. The nucleus contains the chromosomes, which carry genes. Mitochondria are the powerhouse of the cells. A plant cell has a big central vacuole unlike a number of small vacuoles in animal cells. Plant cells possess plastids, which are of three types namely: chloroplasts, chromoplasts, and leucoplasts. Prokaryotic cells lack membrane-bound organelles whereas eukaryotic cells possess membrane-bound organelles. Please refer ​Cell Structure and Functions Class 8 Extra Questions​ for more information.

9. Reproduction in Animals Class 8 Extra Questions CBSE Reproduction in Animals Class 8 Extra Questions Reproduction is essential for the continuation of life on Earth. There are two modes by which animals reproduce: Sexual reproduction and asexual reproduction. Reproduction resulting from the fusion of male and female gametes is called sexual reproduction. The

reproductive organs in male include testes, sperm ducts, and penis. Testes produce the sperms. The structure of sperm comprises Head, middle piece and tail. The reproductive organs in the female include ovaries, oviducts, and uterus. The ovary produces female gametes called ova or egg. The fusion of ovum and sperm is called fertilization. Please refer R ​ eproduction in Animals Class 8 Extra Questions​ for more information.

10. Reaching the Age of Adolescence Class 8 Extra Questions CBSE Reaching the Age of Adolescence Class 8 Extra Questions

● Between the ages of 11 and 19 years, children are called adolescents. Adolescents are also called ‘teenagers’. Humans become capable of reproduction after the onset of puberty. ● In females, maturation and release of ova start from the age of 10-12 years.

Menstrual flow commences at puberty, which is called menarche. It stops at the age of 45-50, which is called menopause. When the state of well being is with special reference to reproductive conditions, it is reproductive health. Please refer ​Reaching

the Age of Adolescence Class 8 Extra Questions​ for more information.

11. Force and Pressure Class 8 Extra Questions CBSE Force and Pressure Class 8 Extra Questions Force is a push or pulls applied on an object. The motion imparted to objects is due to the action of the force. A force applied, produces an interaction between the two bodies. The net force on a body depends on the magnitude and direction. A force applied on an object may bring the change in the state of the object and even can change its shape.

There are two types of forces: Contact forces and non – contact forces. The contact between the bodies is necessary in case of contact forces. In the case of non-contact forces, direct contact between the interacting bodies is not necessary. Please refer F ​ orce

and Pressure Class 8 Extra Questions f​ or more information.

12. Friction Class 8 Extra Questions CBSE Friction Class 8 Extra Questions Friction is the opposing force that comes into play when one body moves or tries to move over another body. Friction depends on the nature of the surfaces in contact, how hard the two surfaces pressed together. For a given pair of surfaces, friction depends upon the state of smoothness of those surfaces.

The three types of friction are static, sliding and rolling frictions. Static friction is the friction which acts on an object when we try to move an object from rest. Sliding friction is the friction which acts on an object when it is sliding over another object. Rolling friction is the friction which comes into play when one body rolls over another body. Friction is both a necessity and an evil for us. It has both advantages and disadvantages. To increase the force of friction, we need to increase the roughness of the two surfaces in contact. Please refer F ​ riction Class 8 Extra Questions​ for more information.

13. Sound Class 8 Extra Questions CBSE Sound Class 8 Extra Questions Sound in the form of energy that causes a sensation of hearing. The vibration of an object is the necessary condition for the production of sound. In humans, the sound is produced by

the voice box or larynx. Sound needs a material medium for its propagation. Sound travels through solids, liquids, and gases but it cannot travel through a vacuum. Hearing is the process in which eardrum senses the vibrations of sound and sends the signals to the brain. Properties of sound enable us to distinguish between two sounds produced by a different source. The two important properties of sound are amplitude and frequency.

Amplitude is the maximum displacement of a body from its mean position. Please refer

Sound Class 8 Extra Questions​ for more information.

14. Chemical Effects of Electric Current Class 8 Extra Questions CBSE Chemical Effects of Electric Current Class 8 Extra Questions The liquids that allow electricity to pass through them are known as good conductors. The liquids that do not allow electricity to pass through them are known as poor conductors.

The conductivity of liquids can be checked by using the tester circuit. There are two types of tester circuit: one uses bulb or LED and another uses a magnet. Liquids that conduct electricity are solutions of acids, bases, and salts. The passage of an electric current through a conducting liquid causes chemical reactions. The process of depositing a layer of any desired metal on another material by means of electricity is known as electroplating.

The layer of metal deposited has some desired property which the metal of the object lacks.

Please refer C ​ hemical Effects of Electric Current Class 8 Extra Questions​ for more information.

15. Some Natural Phenomena Class 8 Extra Questions CBSE Some Natural Phenomena Class 8 Extra Questions Some objects get charged when rubbing with some other specific object. The electrical charges produced by rubbing are static. There are two types of charges: positive charge and

negative charge. Like charges repel and unlike charges attract each other. An electric current is produced when charges move. The electrical charge can be transferred from a charged object to another through a metal conductor. The device used to detect charge is known as electroscope. The process of transfer of charge from a charged object to the earth is known as earthing. Lightning is the process of discharge between the clouds and the earth or between different clouds. Please refer ​Some Natural Phenomena Class 8

Extra Questions​ for more information.

16. Light Class 8 Extra Questions CBSE Light Class 8 Extra Questions Light is a form of energy that causes a sensation of vision. When the light falls on a polished or shiny surface it gets reflected back into the same medium. We see the things around us when reflected light from the object enters our eyes. Reflection of light takes place in accordance with the two laws of reflection. The incident light reflected light and the normal at the point of incidence, all lie in the same plane. The angle of incidence is always equal to the angle of reflection. When light rays coming from an object incident on a plane mirror, the image formed is laterally inverted i.e., left the side of the object appears as a right side in the mirror r and vice-versa and the phenomenon is called lateral inversion.

Please refer L ​ ight Class 8 Extra Questions​ for more information.

17. Stars and the Solar System Class 8 Extra Questions CBSE Stars and the Solar System Class 8 Extra Questions The stars, the planets, the moon and many other objects in the sky are called celestial objects. Moon is the brightest object in the night sky. The moon revolves around the earth and is the natural satellite of the earth. There are various shapes of the bright part of the moon which can be seen during a month. We see only that portion of the moon from where

the sunlight gets reflected towards us. The size of the illuminated part of the moon visible from the earth keeps on changing every day which leads to phases of the moon. On observing the closure view of the moon, it is found that the moon’s surface is dusty and barren. Please refer S ​ tars and the Solar System Class 8 Extra Questions​ for more information.

18. Pollution of Air and Water Class 8 Extra Questions CBSE Pollution of Air and Water Class 8 Extra Questions The introduction of contaminants into the environment, which can cause harm to human beings, other living organisms, and the environment, is called pollution. The substances that contaminate air, water and soil are known as pollutants. Pollution is classified as air pollution, water pollution, soil pollution, and noise pollution. The sources of air pollution can be natural or man-made. Smog, chlorofluorocarbons and sulfur dioxide act are common air pollutants. When rainwater dissolves the oxides of sulfur and nitrogen, acid rain is formed.

Greenhouse effect and global warming are the major effects of air pollution on climate and environment. Air pollution can be controlled by planting trees. Please refer P ​ ollution of Air

and Water Class 8 Extra Questions​ for more information.

Â