Class 10 Science: CBSE Sample Question Paper (2019-20) - 3 | CBSE Sample Papers For Class 10 PDF Download

Class-X
Science-086
SAMPLE QUESTION PAPER 2019-20

TIME: 3 Hrs.
M.M: 80

General Instructions:
1. The question paper comprises three sections - A, B and C. Attempt all the sections.
2. All questions are compulsory.
3. Internal choice is given in each section.
4. All questions in Section A are one - mark questions comprising MCQ, VSA type and
assertion-reason type questions. They are to be answered in one word or in one sentence.
5. All questions in Section B are three - mark, short - answer type questions. These are to be answered in about 50 - 60 words each.
6. All questions in Section C are five - mark, long - answer type questions. These are to be answered in about 80 - 90 words each.
7. This question paper consists of a total of 30 questions.

Section - A

Q.1. A ray of light passes through a medium of refractive index 4/3, then the speed of light ray in medium is (Given, speed of light in air, c = 3 x 10⁸ m/s)    (1 Mark)
Ans: Refractive index of medium, n = 4/3
∴
⇒
⇒

Q.2. When the light is very bright    (1 Mark)
(a) the iris makes the pupil expand.
(b) the iris makes the pupil contract.
(c) ciliary muscles contract to make the eyelens thicker.
(d) ciliary muscles expand to make the eyelens thinner.
Ans: (b) When the light is very bright the iris makes the pupil contract so as to control the quantity of light entering the eye.

Q.3. Answer question numbers 3(a) - 3(d) on the basis of your understanding of the following paragraph and the related studied concepts.
Operating on the same principle as wind turbines, the power in sea turbines comes from tidal currents, which turn blades similar to ships' propellers, but, unlike wind, the tides are predictable and the power input is constant. The technology raises the prospect of many countries becoming self-sufficient in renewable energy and drastically reducing its carbon dioxide emissions. If tide, wind and wave power are all developed, Britain would be able to close gas, coal and nuclear power plants and export renewable power to other parts of Europe. Unlike wind power, which Britain originally developed and then abandoned for 20 years allowing the Dutch to make it a major industry, undersea turbines could become a big export earner to island nations such as Japan and New Zealand.
(a) On what principle do the sea turbines operate?    (1 Mark)
(b) What is the advantage of sea turbines over wind turbines?    (1 Mark)
(c) If tide, wind and wave power are used by Britain which other energy sources are likely to be closed by it?    (1 Mark)
(d) For which countries sea turbines can become a good source of energy?    (1 Mark)
Ans: (a) Wind turbines.
(b) Unlike the wind the tides are predictable hence, power input is constant.
(c) Gas, coal and nuclear plants.
(d) Japan and New Zealand.

Q.4. A beam of white light falling on a glass prism gets split into seven colours marked 1 to 7.

(a) The colour at positions marked 1 and 3 are similar to the colour of 'turmeric' and the colour of 'Chilli powderrespectively. Is the above statement correct or incorrect?    (1 Mark)
(b) Which two positions correspond to the colour of solution of copper sulphate and signal used to move the vehicles?    (1 Mark)
(c) Light of colour of chilli powder bends the most while the light of colour of brinjal bends the least. Is the statement correct?    (1 Mark)
(d) Which of the following statements is correct regarding the propagation of light of different colours of white light in air?    (1 Mark)
(i) Red light moves fastest
(ii) Blue light moves faster than green light
(iii) All the colours of the white light move with the same speed in air
(iv) Yellow light moves with the mean speed as that of the red and the violet light
Ans: (a) Incorrect
3 - turmeric (yellow)
1- chilli powder (red)
(b) Copper sulphate — (blue colour) — position—5
Green light - position - 4
(c) Incorrect, violet bends the most.
(d) (iii) All the colours of white light move with the same speed in air

Q.5. A flower can self-pollinate only, if it contains
(a) only anther
(b) only ovary
(c) Both (a) and (b)
(d) Either (a) or (b)
Or
Which of the following substances is exchanged between mother and foetus through the placenta?    (1 Mark)
(a) Glucose
(b) Oxygen
(c) Carbon dioxide
(d) All of these
Ans: (c) The pollen needs to be transferred from the stamen to the stigma, so that the fusion of germ cells, i.e., fertilisation can occur. If this transfer of pollen occurs in the same flower, it is called self-pollination and a flower needs both the anther and the ovary for it.
Or
(d) The embryo gets nutrition from the mother's blood with the help of a specialised tissue called placenta, Bfood spaces on the mother’s side of the placenta provide surface area for glucose and oxygen to pass from mother to embryo. Also, the w aste sub stances generated by embryo (urea and CO₂) are removed through the placenta.

Q.6. The flowers that act as indicators are    (1 Mark)
(a) hydrangea
(b) Petunia
(c) geranium
(d) All the above
Ans: (d) All the above

Q.7. A cell, a resistor, a key and ammeter are arranged as shown in the circuit diagrams of Figure. The current recorded in the ammeter will be    (1 Mark)

(a) maximum in (i)
(b) maximum in (ii)
(c) maximum in (iii)
(d) the same in all the cases
Ans: (d) Same in all the cases.

Q.8. Where would you locate the element with electronic configuration 2, 8 in the Modern Periodic Table?    (1 Mark)
(a) Group 8
(b) Group 2
(c) Group 18
(d) Group 10
Ans: (c) Element with electronic configuration 2, 8 has complete octet configuration, so must be placed in group 18.

Q.9. The strength of the acid depends on the    (1 Mark)
(a) number of hydrogen atoms present in the molecule 
(b) density of molecule 
(c) oxygen content present in the molecule 
(d) concentration of hydrogen ions furnished by the acid
Ans: (d) The strength of the acid depends on the concentration of hydrogen ions furnished by the acid.

Q.10. Which of the following statement (s) is (are) true about respiration?    (1 Mark)
(i) During exhalation, ribs move inwards and diaphragm is lowered.
(ii) Exchange of gases takes place in alveoli.
(iii) During inhalation, ribs move outwards and diaphragm is lowered.
(iv) Haemoglobin has greater affinity for carbon dioxide.
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (iii) and (iv)
Ans: (b) During inhalation, diaphragm is lowered and ribs move outward resulting in increased volume of lungs so air rushes in. Exchange of gases occur in alveoli.

Q.11. 10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount HCl solution (the same solution as before) required to neutralise it will be;    (1 Mark)
(a) 4 mL
(b) 8 mL
(c) 12 mL
(d) 16 mL
Ans: (d) 16 mL

Q.12. Which of the following oxide(s) of iron would be obtained on prolonged reaction of iron with steam?    (1 Mark)
(a) FeO
(b) Fe₂O₃ 
(c) Fe₃O₄ 
(d) Fe₂O₃ and Fe₃O₄
For question numbers 13 and 14, two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (i), (ii), (iii) and (iv) as given below:
(i) Both A and R are true and R is correct explanation of the assertion.
(ii) Both A and R are true but R is not the correct explanation of the assertion.
(iii) A is true but R is false.
(iv) A is false but R is true.
Ans: (c) Iron reacts only with steam to form a metal oxide and hydrogen.


Q.13. For each of the following questions, two statement are given one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer as to these questions from the codes (i), (ii), (iii) and (iv) as given below.    (1 Mark)
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. 
(b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. 
(c) If Assertion is true, but Reason is false. 
(d) If Assertion is false, but Reason is true.
Assertion When a charged particle enters in the direction of a uniform magnetic field, then it moves on a straight path without deviation.
Reason Magnetic force on a charged particle is zero, when it moves in the direction of magnetic field.
Ans: (a) When a charged particle enters in the direction of magnetic field, then no magnetic force acts on charged particle, hence it moves on a straight path without deviation in uniform magnetic field,

Q.14. Absorption of digested food occurs throughout the alimentary canal.    (1 Mark)
Ans: False - Absorption of digested food takes place in small intestine as villi are present there.

Section B

Q.15. B₁, B₂ and B₃ are three identical bulbs connected as shown in the figure. Ammeters A₁, A₂ and A₃ are connected as shown in figure. When all the bulbs glow, then the current of 3 A is recorded by ammeter A.    (3 Mark)

What happend to the reading of A₁, A₂ when the bulb B₂ gets fused?
Or
Three incandescent bulbs of 100W each are connected in series in an electric circuit. In another circuit, another set of three bulbs of the same wattage are connected in parallel to the same source. Will the bulb in the two circuits glow with the same brightness? Justify your answer.
Ans: Resistance of combination of three bulbs in parallel, is expressed as,
 
If R is the resistance of each wire, then

or
or    
Current in each bulb,
When bulb B₂ gets .fused, then the current in B₂ becomes zero and currents in B1 and B₃ remain 1 A.
 
Or
Let us assume that the resistance of each bulb be R. The circuit diagram in two cases may be drawn as given below:
(A)
(B)    
In series circuit (a)
Equivalent resistance in series combination, R_s = R + R + R = 3R, Voltage = V
Let current through each bulb in series combination be I₁,  (∵ Current remains same in series combination) By Ohm’s law,

∴ Power consumption of each bulb in series combination,
 ...(i)
In parallel circuit (b)
The resistance of each bulb = R
Voitage across each bulb = V (∵ Voltage remains same in parallel combination)
∴ Power consumption of each bulb in parallel combination,
 ...(ii)
Hence, from Eqs. (i) and (ii), we get

Therefore, each bulb in parallel combination glows 3 times brighter to that of each bulb in series combination.

Q.16. Name two energy sources that you would consider to be renewable. Give justification for your choices. Can these energy sources be pollution free ? List two reasons in support of your answer.    (3 Mark)
Ans: Solar energy and wind energy are renewable sources of energy due to the following reasons:
(i) These forms of energy are available in plenty in our natural environment in the form of continuous currents of energy
(ii) These energy sources will not be depleted because their supply is large and extraction of usable energy from these sources is negligible.
These energy sources are mostly pollution free on account of the following reasons :
(i) They do not need any fuel and do not produce any ash/waste.
(ii) They do not produce any smoke and do not cause green house effect.
However, some pollution may be caused during the manufacture of solar cells and wind power generators.

Q.17. The modem periodic table has been evolved through the early, attempts of Dobereiner, Newland and Mendeleev. List one advantage and one limitation of all the three attempts.    (3 Mark)
Ans:

Q.18. Write three types of blood vessels. Give one important feature of each.    (3 Mark)
Ans: Arteries - No valves/thick walled/carry oxygenated blood/carry blood away from heart.
Veins - Presence of valves/thin walled/carry deoxygenated blood/carry blood towards heart.
Capillaries - Very fine/mixed blood/found in tissues/sites for material exchange.

Q.19. 'Reproduction is not necessary to maintain the life of an individual, unlike other life processes such as nutrition, respiration or excretion. Still, an individual wastes energy for reproduction. Derive your own conclusion from the above given statement and describe it accordingly.    (3 Mark)
Ans: Reproduction is the ability of a living organism to produce new individuals similar to them. Like other essential life processes (nutrition, respiration, growth and excretion), reproduction is not essential to maintain the life of an individual. However, it is essential for the purpose of
• continuation of life on the Earth.
• addition of new species.
• replacement of dead organisms.
• transfer of variations from one generation to another.

Q.20. List four functions of the human heart. Why is double circulation necessary in the human body?    (3 Mark)
Ans: Four functions of human heart are:
(i) It receives deoxygenated blood from the body for oxygenation.
(ii) Sends the blood to the lungs for oxygenation.
(iii) Receives oxygenated blood from the lungs to be supplied to body.
(iv) Sends oxygenated blood to various body parts, so that each cell gets energy.
Double circulation is necessary for human body. It ensures quick and efficient supply of oxygenated blood to all body parts for meeting higher energy needs and for thermoregulation of body in mammals and birds.

Q.21. Name the hormones secreted by the following endocrine glands and specify one function of each:    (3 Mark)
(a) Thyroid
(b) Pituitary
(c) Pancreas
Ans: 

Q.22. (a) Define electromagnetic induction.    (3 Mark)
(b) Two coils P and S are wound over the same iron core. Coil P is connected to battery and key and the coil S is connected to galvanometer. Write your observations when:

(i) Current in the coil P is started by closing the key.
(ii) Current continues to flow in coil P
(iii) Current in coil P is stopped by removing the key.
Explain the reason for such observation.
Ans: (a) Electromagnetic induction : The process by which a change in magnetic field in a conductor induces a current in another conductor.
(b) (i) There is deflection in galvanometer connected with coils, due to induced current.
(ii) Deflection becomes zero.
(iii) Deflection in galvanometer is in opposite direction.
Reasons:
(i) E.M. induction takes place because field is changing.
(ii) Since current becomes stationary, no change in field takes place. So, there is no E.M. induction.
(iii) E.M. induction takes place but the induced current is in opposite direction.

Q.23. A household uses the following electric appliances.    (3 Mark)
(i) A heater of rating 1000 W for 5 hours in each day.
(ii) 5 electric bulbs of rating 100 W each for 5 hours in each day (given, cost of electrical energy ₹ 2.5 per unit).
Find the electricity bill for the household for the month of April.
Ans: Total number of units consumed by heater for 5 hours each day in one month,

Cost of electrical energy consumed by heater in month of April = 150 x 2.5 = ₹375
Total number of units consumed by 5 electric bulbs in one month,

Cost of electrical energy consumed by 5 bulbs in one month = 75 x 2.5 = ₹ 187.5
Electricity bill for the month of April = ₹ 375 + ₹ 187.5 = ₹ 562.5
Alternate solution
Total power consumed by electric appliances (heater and 5 bulbs) per day,
P = 1000 + 100 x 5
= 1500 watt
Total number of hours of operation of electric appliances in a month of April,
= 5 x 30 = 150 hours
∴ Total number of units
∴ Electricity bill for the month of April = 225 x 2.5 = ₹ 562.5

Q.24. List in tabular form three distinguishing features between cerebrum and cerebellum.    (3 Mark)
Ans:

Section C

Q.25. (i) What are decomposers? What will be the consequence of their absence in an ecosystem?
(ii) Which of the following is always present at the third trophic level in a food chain? Carnivores, Herbivores, Producers.    (5 Mark)
Ans: (i) Organisms which breakdown the complex organic compounds present in the dead and decaying matter are called decomposers, e.g. certain bacteria and fungi.
Decomposers act as cleaning agents of the environment by decomposing the dead bodies of plants and animals. They also help in recycling and replenishment of soil’s nutrients, etc.
The consequence of their absence in an ecosystem can be disastrous as discussed below
(a) The dead bodies would keep getting accumulated and thus, pollute the environment.
(b) The elements of which bodies are made, would never be returned to the environment. As a result, all the nutrients present in soil, air and water would soon be exhausted and the whole life cycle of organisms will be disrupted.
(ii) In the food chain, the third trophic level is always occupied by carnivores that feed on herbivores. Plants occupy the first trophic level, herbivores constitute the second trophic level, carnivores constitute the third trophic level and in some food chains large carnivores occupy the fourth trophic level.

Q.26. (a) Three resistors of resistances R₁, R₂ and R₃ are connected (i) in series, and (ii) in parallel. Write expressions for the equivalent resistance of the combination in each case. 
(b) Two identical resistors of 12 Ω each are connected to a battery of 3 V.Calculate the ratio of the power consumed by the resulting combinations with minimum resistance and maximum resistance.
Or
(а) Write the relation between resistance and electrical resistivity of the material of a conductor in the shape of a cylinder of length 'I' and area of cross-section ‘A’. Hence, derive the S.I. unit of electrical resistivity.
(b) Resistance of a metal wire of length 5 m is 100 Ω. If the area of cross-section of the wire is 3 x 10^-7 m², calculate the resistivity of the metal.    (5 Mark)
Ans: (a) (i) Let three resistors of resistances R₁, R₂ and R₃ are connected in series then the equivalent resistance R_s is equal to the sum of the three individual resistances.
Mathematically,
R_s = R₁ + R₂ + R₃
(ii) If the same resistances are connected in parallel then the sum of the reciprocals of individual resistances gives the reciprocal of their equivalent resistance R_p.
Mathematically,

(b ) Here resistances R₁ = R₂ = 12Ω and voltage o f battery V = 3 V.
When the resistances on combination given a minimum resulting resistance, the two resistances are connected in parallel and equivalent resistance R_p is given as:

⇒ R_p = 6Ω
∴ Power in this arrangement
When resistances are combined so as to give maximum resistance, they have been connected in series and the equivalent resistance R_s is then given as :

∴ Power in this arrangement
⇒
Or
(a) The resistance R and electrical resistivity p of the material of a conductor in the shape of a cylinder of length 'l' and area o f cross-section ‘A ’ are correlated as :

∴ SI unit of electrical resistivity p = SI unit of
Thus, SI unit of electrical resistivity is ohm-metre (Ω-m)
(b) Here length of metal wire l = 5 m, resistance of wire R = 100 Ω and its area of cross-section A = 3 x 10^-7 m².
∴ Resistivity o f the metal

Q.27. (a) Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms tike humans?
(b) What criteria do we use to decide whether something is alive?    (5 Mark)
Ans: (a) In the multicellular organisms, all the cells may not be in direct contact with the surrounding environment. Therefore, the diffusion is insufficient to meet the oxygen requirements in them. Instead, they need specialised organs for breathing and exchange of gases.
(b) The following criteria is taken into account before deciding whether a thing is alive or not :
(i) All living things breathe.
(ii) All living things grow.
(iii) All those things which are green and growing are also living.
(iv) All living things repair and reproduce.
(v) All living things have a definite lifespan.
(vi) All living things have ability to evolve.
(vii) All living things have the ability to convert simple things into complex things.
(viii) Most of the living things has the ability to move.

Q.28. When do we consider a person to be myopic or hypermetropic? List two causes of hypermetropia. Explain using ray diagrams how the defect associated with hypermetropic eye can be corrected.    (5 Mark)
Ans: Myopia: Difficult to see the objects placed far away / Hypermetropia : Difficult to see very close or nearby objects.
Causes of hypermetropia: (i) The focal length of the eye lens is loo long (ii) eye ball has become too small.

Note: Diagram with brief description -03; only correct diagram with labelling -2 or only explanation 01.

Q.29. (i) Mention any two precautions to avoid the overloading of domestic electric circuits.
(ii) Draw magnetic lines of force for a current carrying solenoid. Also, explain the pole formation at this ends.    (5 Mark)
Ans: (i) The following precautions shouid be taken to avoid the overloading of domestic electric circuits as given below:
(a) The circuits should be of proper current rating and appliances should be accordingly connected.
(b) Wires should be checked from time to time and those wires whose insulation is worn, should be immediately replaced.
(ii) Magnetic lines of force due to a current carrying solenoid are as shown below:

Pole formation at the ends of the solenoid can be explained by looking at one face of the coil. If the direction of current through the coil is clockwise, then that face has South polarity and if the direction of current is anti-clockwise, then that face has North polarity.

Q.30.  (a) What is reproduction? List its two types.
(b) How are the modes of reproduction different in unicellular and multicellular organisms?
Or
(i) What are Sexually Transmitted Diseases (STD)? List two viral and two bacterial STDs. 
(ii) What is contraception? List three reasons for adopting contraceptive methods.    (5 Mark)
Ans: (a) Reproduction is the process by which an organism produces new individuals that look very much like themselves.
It is of two types -
(i) Asexual - Involves only one parent.
(ii) Sexual - Involves two parents.
(b) Difference between modes of reproduction in unicellular and multicellular organisms:

Or
(a) Sexually transmited diseases (STD) are those diseases that are transmitted through sexual contact. They can be bacterial or viral.
For example — Viral diseases are Warts and AIDS
Bacterial diseases are Syphilis and Gonorrhoea.
(b) Contraception - It is a method adopted for prevention of pregnancy.
• They help in spacing two children.
• Thus helps in maintaining a woman’s and child’s health.
• Better care and healthier society.
• Also prevention of sexually transmitted diseases on using condoms.
• More productivity and hence better economic status.