CBSE Class 10 Science Board Exam 2020 Solution Set 1 by AGLASEM

Central Board of Secondary Education (CBSE) conducted the science paper, for the 2020 board exams, on March 4, 2020. After the exam now the solutions to the paper have been compiled, so that students can know answers to questions asked in the paper. Questions asked, their proposed answers, as well as solutions by AGLASEM are here on this page. You can go through it all to calm down yourself over your exam performance. And best wishes for your result!

CBSE Class 10 Science Board Exam 2020 Set 1 Question Paper and Solutions by Aglasem

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CBSE Class 10 Science Board Exam 2020 Solution Set 1 by AGLASEM – Code 31/3/1

CBSE Class 10 Science Board Exam 2020 Solution Set 1 by AGLASEM – Code 31/4/1

Qs 1. The number of valence electrons in a Nitrogen atom

Ans 1. 5 Valence electrons

Qs 2. Define the term induced electric current.

Ans 2. Induced current is the current produced by change in magnetic flux. According to FARADAY’S LAW when there is change in magnetic flux over wire, then a current is produced in the wire, such current is called induced current.

Qs 3. Answer questions based on paragraph (on Mendeleev)

Ans a). Mendeleev’s Periodic Law states that the physical and the chemical properties of the elements are a periodic function of their atomic masses.

Ans b). Mendeleev left some gaps in the periodic table as mendeleev’s classification could not assign position to isotopes.

Ans c). RH4,RO

Ans d). 1

Qs 4. Answer questions based on paragraph (on resource utilization)

Ans a). Curbside Collection and Drop-off Recycling

Ans b). Water Bottles, Plastic carry bags

Ans c). If we discontinue the use of plastic, an environment-friendly substitute can be provided by effective plastic waste collection and methods of its disposal.

Ans d). Yes. Microorganisms recycle nutrients in the environment, by decomposing organic materials. Organic materials, such as animal carcasses and tree trunks, decay by the action of decomposing microbes, which are also responsible for getting rid of industrial and household waste. Through a process called biodegradation, microbes use nutrients and chemical substances found in the environment for their own survival. The nutrients from the breakdown of these products are free in the environment to feed plants or algae, which in turn feed all animals.

Qs 5. Which statement is correct about human circulatory system?

Option a. Blood transports only oxygen and not carbon dioxide.
Option b. Human heart has five chambers.
Option c. Valves ensure that the blood does not flow backwards.
Option d. Both oxygen-rich and oxygen-deficient blood gets mixed in the heart.

Ans. C.

Qs 6. Anaerobic process

Option a. Takes place in yeast during fermentation.
Option b. Takes place in presence of oxygen.
Option c. Produces only energy in the muscles of human beings.
Option d. Produces ethanol, oxygen, energy.

Ans. A.

Qs 7. Fertilization is the process of

Option a. Transfer of male gamete to female gamete.
Option b. Fusion of nuclei of male and female gamete.
Option c. Adhesion of male and female reproductive organs.
Option d. The formulation of gametes by reproductive organ.

Ans. B.

Qs 8. If a person has five resistors each of value 1/5 ohm, then the maximum resistance he can obtain by connecting them is

Option a. 1 ohm
Option b. 5 ohm
Option c. 10 ohm
Option d. 25 ohm

Ans. A.

OR Qs 8. The resistance of a resistor is reduced to half of its initial value. In doing so, if other parameters of the circuit remain unchanged, the heating effectes in the resistor will become

Option a. Two times
Option b. Half
Option c. one-fourth
Option d. four times

Ans. B.

Qs 9. Fleming’s right hand rule gives

Option a. magnitude of the induced current.
Option b. magnitude of the magnetic field.
Option c. direction of the induced current.
Option d. both, direction and magnitude of the induced current.

Ans. C

Qs 10. Which one of the following statements is not true about nuclear energy generation in a nuclear reactor?

Option a. Energy obtained by a process called nuclear fission.
Option b. The nucleus of Uranium is bombarded with high energy neutrons.
Option c. A chain reaction is set in the process.
Option d. In this process a tremendous amount of energy is released at a controlled rate.

Ans. B.

OR Qs 10. The biggest source of energy on Earth’s surface is

Option a. Biomass
Option b. Solar radiations
Option c. Tides
Option d. Winds

Ans. B.

Qs 11. Food web is constituted by

Option a. relationship between the organisms and the environment.
Option b. relationship between plants and animals.
Option c. various interlinked food chains in an ecosystem.
Option d. relationship between animals and environment.

Ans. C.

Qs 12. Choose the incorrect statement from the following

Option a. Ozone is a molecule formed by three atoms of oxygen
Option b.
Option c.
Option d.

Ans. C.

Ans 13. C

Ans 14. A

Ans 15. a) A bright yellow precipitate of lead iodide is precipitated

b) Pb(NO3)2 + 2KI —> PbI2 + 2KNO3

c) Double Displacement reaction as the two compounds react, and the positive ions and negative ions of the two reactants switch places, creating two new compounds.

OR

Rancidification. Rancidification is the process of complete or incomplete oxidation or hydrolysis of fats and oils when exposed to air, light, or moisture or by bacterial action.

Observational changes:
1.Change in smell
2.Change in taste

Prevention :
1.By keeping the food in airtight container.
2.By lowering the temperature.
3.By vacuum packing.

Ans 17. Carbon forms large number of compound due to following reasons:

1. Catenation: The unique property of the ‘C’ element to be able to form continuous links with other ‘C’ atoms through covalency called catenation, is one reason for the existence of a large number of organic compounds.
2. Tetravalency: The carbon atom’s four valence electrons can be shared by other atoms that have electrons to share, thus forming covalent (shared-electron) bonds. They can even be shared by other carbon atoms, which in turn can share electrons with other carbon atoms and so on, forming long strings of carbon atoms, bonded to each other like links in a chain.
3. Isomerism: The same collection of atoms and bonds, but in a different geometrical arrangement within the molecule, makes a molecule with a different shape and hence different properties. These different molecules are called isomers.
4. Multiple Bond: Carbon atoms can share not only a single electron with another atom to form a single bond, but it can also share two or three electrons, forming a double or triple bond.

Ans 18. Nerve Impulse and Structure of Special Proteins in Muscle Fibre. On seeing the prey, an impulse is sent from the brain to the muscles in it’s limbs so that the cheetah can run towards the prey. Muscles have special proteins that change both their shape and their arrangement in the cells, new arrangement of the proteins give different forms to the muscle cells, i.e. Shorter or Larger form.

Therefore, the cheetah is able to run after the prey due to the arrangement of cellular components (proteins) in the muscles.

Ans 19. Geotropism is the response to gravity in which different parts of a plant grow in opposite directions like a root grows downwards whereas the stem grows upwards.
It’s two states are :
(1) POSITIVE GEOTROPISM (growing with gravity)
(2) NEGATIVE GEOTROPISM (growing against gravity)

Diagram:

Ans 20. Evolution is a gradual and continuing process of change that occurs over a period of time, due to slight variations in genetic compositions as well as changes in environment, leading to formation of new species.
Evolution cannot be equated with progress because it is used to describe the slow and gradual process by which living organisms have undergone changes from the simplest unicellular forms of life to the most complex multicellular forms that can be seen today.

OR

Organs or features can be adopted to new . functions during evolution Example – Feathers were developed form providing insulation in cold weather (in dinosaurs) but in birds they were adopted for flight.

Ans 23 a).
b). It happens when a person is not able to see both near distant & far distant objects.
c). Bifocal Lenses

Ans 27 a). All living organisms need energy to perform various life processes. They get this energy from food. Food consists of nutrients which are required by the body to convert it into smaller molecules which can be absorbed by the body to perform daily life tasks.

b). Peristalsis mainly causes movement of food inside the alimentary canal. The contraction and expansion of oesophagus is known as Peristalsis movement.

c). Herbivorous animals have longer intestines than that of carnivorous animals. This is because their diet is grass and plants, made up of fibre and cellulose which are hard to digest. As a result the herbivorous animals need a longer digestive tract to digest their foods completely.

d). Gastric glands in the stomach release hydrochloric acid, enzyme pepsin and mucus. The mucus protects the inner lining of the stomach from the action of hydrochloric acid and enzyme pepsin. If mucus is not released, it will lead to erosion of the inner lining of the stomach, which may cause acidity and ulcer.

Ans 30. a).Fleming’s left-hand rule states that if we stretch the thumb, the forefinger and the middle finger of our left hand such that they are mutually perpendicular to each other.

If the forefinger gives the direction of current and middle finger points in the direction of magnetic field then the thumb points towards the direction of the force or motion of the conductor.

c). A fuse is a device that is fitted in an electric circuit with the purpose of protecting the wiring from excessive currents. A fuse is an electrical safety device that has the capability to protect an electric circuit from excessive electric current. It is designed to allow current through the circuit, but in the event that the current exceeds some maximum value it will open, severing the circuit.

d).The main function of the earth wire is to conduct the leaking current from the electrical appliance to the ground . It is connected to the outer metallic body of the appliance .
It is necessary to earth metallic appliances , as it protects the user from electric shocks by transferring the current to the earth.

These answers are in the order they appeared in 31/3/1, 31/4/1. If you got another set 1 paper, please match questions with answers, rather than question number with answer. If none of the questions provided here came in your paper, please send your paper to [email protected] We will try to provide solutions to your paper as well..

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