# HBSE Class 10th Science Solved Question Paper 2021

HBSE Class 10th Science Solved Question Paper 2021

HBSE Class 10 Science Previous Year Question Paper with Answer. HBSE Board Solved Question Paper Class 10 Science 2021. HBSE 10th Question Paper Download 2021. HBSE Class 10 Science Paper Solution 2021. Haryana Board Class 10th Science Question Paper 2021 Pdf Download with Answer.

Subjective Questions

Q1. On what factors does the resistance of a conductor depend ?

Ans. Resistance of a conductor depend on :

(i) Length of the wire

(ii) Area of cross-section of the wire

(iii) Nature of material of the wire.

Q2. Find the focal length of a lens of power +2.0D. What type of lens is this ? Write one use of this lens.

Ans. P=1/F,   F=1/P = 1/2 = + 0.5 m

Uses of Convex Lens : It is use in microscopes and magnifying glasses to subject all the light to a specific point. It is use as a camera lens in cameras as they focus light for a clean picture. It is use in the correction of hypermetropia.

Q3. Explain principle and working of an electric motor by drawing a labelled diagram.

Ans. Principleâ€“ An electric motor is a rotating device that converts electrical energy to mechanical energy working.

Workingâ€“ Current in the coil ABCD enters from the source battery through conducting brush X and flow back to the battery through brush Y. Notice that the current in the arm AB of the coil flows from A to B. In arm CD it flows from C to D that is opposite to the direction of current through arm AB on applying Flemingâ€™s left hand rule for the direction of force on a current-carrying conductor in a magnetic field. We find that the force acting on arm AB pushes it downwards while the force acting on arm CD pushes it upwards. Thus the coil and the Axle O, mounted free to turn about an axis, rotate anti-clockwise at half rotation. Q makes contact with the brush X and P with brush Y. Therefore the current in the coil gets reversed and flows along the path DCBA. The reversal of current also reverses the direction of force acting on the two arms AB and CD. Thus the arm AB of the coil that was earlier pushed down, is now pushed up and the arm CD previously pushed up is pushed down. There is a continuous rotation of the coil and to the axle.

OR

(a) Draw the magnetic lines of force around a bar magnet.

Ans.

(b) What is Fleming’s left hand rule ? Explain.

Ans. When a current-carrying conductor is placed in an external magnetic field, the conductor experiences a force perpendicular to both the field and to the direction of the current flow. It was invented by John Ambrose Fleming.

Q4. Fat and oil containing foods are packed with which gas and why ?

Ans. Oil and fat containing food items are flushed or surrounded with an inert gas such as Nitrogen while packing them to prevent their contact with oxygen present in the air. This is done to avoid rancidity of fats and oils.

Q5. Write common name and two uses of NaHCO3

Ans. Common name of NaHCOis Baking Soda.

Uses of Baking Soda : Reduces the acidity in the stomach. It is acts as an antacid which is used to treat stomach upset and indigestion. It is used in the process of washing as a water softener. Due to the formation of soapy foam, it is used in fire extinguishers.

Q6. (a) How does atomic size vary in a group ? Explain.

Ans. Atomic size is the distance between the center of nucleus and the outermost electron in the outer shell. Across a period from left to right there is decrease in atomic size with increase in nuclear charge of the element. Atomic size increases down the group because of addition of extra shell

(b) Explain Dobereiner’s law of Triads with one example.

Ans. According to Dobereiner’s law of triads, when elements are arranged in increasing order of their atomic masses, a group of three elements with similar chemical properties is obtained. This group is called a triad. The atomic mass of the middle element is equal to the arithmetic mean of the atomic masses of the other two elements. For example, the set of elements: calcium (Ca), strontium (Sr) and barium (Ba), with atomic masses 40, 88 and 137 respectively form a triad because they have similar chemical properties, and the atomic mass of strontium is approximately equal to the average of the atomic masses of calcium and barium. Arithmetic mean of atomic masses of calcium and barium = (40+137)/2 = 88.5

OR

(a) Name three elements whose valence shell contains one electron.

Ans. Lithium, Sodium, and Potassium

(b) What were the criteria used by Mendeleev in creating his periodic table ?

Ans. Elements are arranged in increasing order of their Atomic mass. Similarity of chemical properties (which he selected as the important factor in arranging elements). i.e. the element with similar chemical properties should be in the same group.

Q7. How is the process of pollination different from fertilization ?

Ans. Pollinationâ€“ The process of transfer of pollen from the male parts (anther) of a flower to the female part (stigma) of the same or different flower is called pollination. It is an external mechanism and takes place on the outer part of a flower. Pollination occurs in flowering plants only. It has two types: Self-pollination, Cross-pollination. No formation of pollen tube. Pollination takes place before fertilization.

Fertilizationâ€“ Fertilization is the common process, involving the union of the male gamete (sperm) and female gamete (egg). It is an internal mechanism and takes place inside the flowers. Fertilization is followed by almost every plant and living being present on earth. It has No types. Formation of pollen tube which helps in transferring of male gametes up to an egg cell. Fertilization takes place after pollination.

Q8. Describe three different methods of contraception.

Ans. Natural Methodâ€“ It involves avoiding the chances of meeting of sperms and ovum. In this method, the sexual act is avoided from day 10th to 17th of the menstrual cycle because, during this period, ovulation is expected and therefore, the chances of fertilization are very high.

Barrier Methodâ€“ In this method, the fertilization of ovum and sperm is prevented with the help of barriers. Barriers are available for both males and females. Condoms are barriers made of thin rubber that are used to cover penis in males and vagina in females.

Oral Contraceptivesâ€“ In this method, tablets or drugs are taken orally. These contain small doses of hormones that prevent the release of eggs and thus fertilization cannot occur.

Implants and Surgical Methodsâ€“ Contraceptive devices such as the loop or Copper-T are placed in the uterus to prevent pregnancy. Some surgical methods can also be used to block the gamete transfer. It includes the blocking of vas deferens to prevent the transfer of sperms known as vasectomy. Similarly, fallopian tubes of the female can be blocked so that the egg will not reach the uterus known as tubectomy.

Q9. (a) Draw a well labelled diagram of Human Excretory System.

Ans.

(b) What are the differences between transport of Materials in xylem and phloem ?

Ans. Xylemâ€“ Xylem transports soluble minerals and water molecules. Water is absorbed by the roots and is transported to the aerial parts of the plant like the stem and leaves. Xylem tissues are composed mainly of dead cells. Transportation in the xylem is unidirectional from roots to leaves. Xylem provides mechanical strength to the plant.Xylem is responsible for the amount of water loss through transpiration and photosynthesis. Xylem consists of tracheids, vessels, parenchyma, and fibers.

Phloemâ€“ Phloem transports food and other nutrients like sugar and amino acids. Food is formed in the leaves from where it is transported to the storage organs and the growing parts of the plants. Phloem tissues are mainly composed of living cells. Phloem transportation is bidirectional from leaves to various plant parts. Phloem transports the sugar in the storage organs. Phloem is responsible for transporting proteins and mRNAs throughout the plant. Phloem consists of sieve tubes, companion cells, parenchyma, fibers.

OR

(a) What are the differences between aerobic and anaerobic respiration ?

Ans. Aerobic Respirationâ€“ Oxygen is required for this type of respiration to take place. It involves the exchange of gases between the organism and the outside environment. Process of respiration takes place in the cytoplasm and the mitochondria. Glucose breaks down or complete oxidation into carbon dioxide and water. All higher organisms such as mammals perform this type of respiration.

Anaerobic Respirationâ€“ No requirement of oxygen in this process. Exchange of gases is there but oxygen gas does not take part. Takes place in the cytoplasm only. Glucose breaks down into ethyl alcohol, carbon dioxide, and energy. Lower organisms such as bacteria or other prokaryotes and yeast follow this type of respiration.

(b) What are the necessary conditions for autotrophic nutrition and what are its byproducts ?

Ans. Autotrophic Nutrition takes place through the process of Photosynthesis. Chlorophyll, carbon dioxide, water and sunlight are the necessary conditions required for autotrophic nutrition. Carbohydrates (food) and oxygen are the by-products of photosynthesis.

Objective Questions (Part-II)

Q1. Which one of the following materials cannot be used to make a lens ?

(A)  Water

(B)  Glass

(C)  Plastic

(D)  Clay

Ans. (D)  Clay

Q2. The change in focal length of an eye lens is caused by the action of the :

(A)  Pupil

(B)  Retina

(C)  Ciliary muscles

(D)  iris

Ans. (C)  Ciliary muscles

Q3. During the burning of a candle the chemical energy converts into :

(A)  Heat energy

(B)  Light energy

(C)  Both A & B

(D)  None of these

Ans. (C)  Both A & B

Q4. Which of the following terms does not represent electrical power in the  circuit ?

(A)  P = VI

(B)  P = IÂ˛R

(C)  P = IRÂ˛

(D)  P = VÂ˛/R

Ans. (C)  P = IRÂ˛

Q5. A solar water heater cannot be used to get hot water on :

(A)  a sunny day

(B)  a cloudy day

(C)  a hot day

(D)  a windy day

Ans. (B)  a cloudy day

Q6. What is the meaning of first ‘R’ in 5 R’s ?

(A)  Reduce

(B)  Reuse

(C)  Recycle

(D)  Refuse

Ans. (D)  Refuse

Order of 5R’sâ€“ (1st)Refuse, (2nd)Reduce, (3rd)Reuse, (4th)Repurpose, (5th)Recycle

Q7. What kind of mirror would be best suited for the use of solar cooker ?

(A)  Convex

(B)  Concave

(C)  Plane

(D)  None of the above

Ans. (B)  Concave

Q8. Tehri Dam is constructed on which river ?

(B)  Godavare

(C)  Ganga

(D)  Yamuna

Ans. (C)  Ganga

Q9. The splitting of white light into seven colours is called :

(A)  Reflection

(B)  Refraction

(C)  Dispersion

(D)  None of these

Ans. (C)  Dispersion

Q10. Which of the following is not an example of a biomass energy source ?

(A)  Wood

(B)  Gobar gas

(C)  Nuclear energy

(D)  Coal

Ans. (C)  Nuclear energy

Q11. Which Acid is present in tamarinds ?

Ans. Tartaric Acid

Q12. Why should Mg ribbon be cleaned before burning in air ?

Ans.

The magnesium ribbon should be cleaned before burning in the air because the layer of magnesium oxide (which is formed due to the reaction of magnesium with air) can be removed in order to get the desired chemistry reaction. Also in order to remove the oxide layer, the presence of which slowdowns the oxidation process. So, by cleaning it, the burning process takes place easily.

Q13. Name a non-metal that possesses lustuer.

Ans. iodine

Q14. Name a metal which is liquid at room temperature.

Ans. Mercury (Hg)

Q15. Name the functional group present in ethanol :

(A)  â€“OH

(B)  â€“CHO

(C)  â€“COOH

(D)  â€“COR

Ans. (A)  â€“OH

Q16. Zn + CuSO4 â†’ ZnSO4 + Cu  is a:

(A)  Combination reaction

(B)  Decomposition reaction

(C)  Double displacement reaction

(D)  Displacement reaction

Ans. (D)  Displacement reaction

Q17. Molecular formula of Methane is :

(A)  CH4

(B)  C2H

(C)  C3H

(D)  C4H10

Ans. (A)  CH4

Q18. The  carbon  compounds  which  contain  just  carbon  and  hydrogen  are  called  :

(A)  Alcohal

(B)  Hydrocarbons

(C)  Aldehyde

(D)  Ketone

Ans. (B)  Hydrocarbons

Q19. The  Xylem  in  plants  are  responsible  for  :

(A)  Transport  of  water

(B)  Transport of food

(C)  Transport  of  amino  acids

(D)  Transport of oxygen

Ans. (A)  Transport  of  water

Q20. The  breakdown  of  pyruvate  to  give  carbondioxide,  water  and  energy,  takes place  in    :

(A)  Cytoplasm

(B)  Mitochondria

(C)  Chloroplast

(D)  Nucleus

Ans. (B)  Mitochondria

Q21. A  sexual  reproduction  takes  place  through  budding  in  :

(A)  Amoeba

(B)  Yeast

(C)  Plasmodium

(D)  Leishmania

Ans. (B)  Yeast

Q22. The  anther  contains  :

(A)  Sepals

(B)  Ovules

(C)  Caspel

(D)  Pollen Grains

Ans. (D)  Pollen Grains

Q23. Which  of  the  following  is  not  a  natural  ecosystem  ?

(A)  Forest

(B)  Pond

(C)  Lake

(D)  Crop Field

Ans. (D)  Crop Field

Q24. Which  of  the  following  are  environment-friendly  practices  ?

(A)  Use  of  cloth  bags

(B)  Switching  off  unnecessary  lights  and  fans

(C)  Walking  to  school

(D)  All  of  the  above

Ans. (D)  All  of  the  above

Q25. Spinal  cord  is  protected  by  :

(A)  Vertebral  column  or  back  bone

(B)  Cranium

(C)  Ribs

(D)  None of these

Ans. (A)  Vertebral  column  or  back  bone

Q26. Control  and  co-ordination  are  the  functions  of  the  hormones  and ……………. in our  body.

(A)  Brain

(B)  Relex  arc

(C)  Nervous  system

(D)  Chemical  Co-ordination

Ans. (C)  Nervous  system

Q27. Which  layer  shields  the  surface  of  earth  from  ultraviolet  radiations  form  Sun ?

Ans. Ozone (O3

Q28. Which  sex  chromosomes  is  present  in  females  ?

Ans. Female – XX,   Male – XY

Q29. The  inner  lining  of  small  intestine  has  numerous  finger  like  projections  called ………..

Ans. Villi

Q30. Mendel  crossed  a  tall  pra  plant  (TT)  and  a  short  plant  (tt)  and  produced progeny  (F1)  from them.  All  plants  were ………..

Ans. Tall

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