CBSE Sample Papers

Students can access the CBSE Sample Papers for Class 10 Science with Solutions and marking scheme Set 4 will help students in understanding the difficulty level of the exam.

CBSE Sample Papers for Class 10 Science Set 4 for Practice

Time: 3 Hours
Maximum Marks: 80

General Instructions:

(i) The question paper comprises four sections A, B, C and D. There are 36 questions in the question paper. All questions are compulsory.
(ii) Section-A – question no. 1 to 20 – all questions and parts there of are of one mark each.
These questions contain multiple choice questions (MCQs), very short answer questions and assertion – reason type questions. Answers to these should be given in one word or one sentence.
(iii) Section-B – question no. 21 to 26 are short answer type questions, carrying 2 marks each. Answers to these questions should in the range of 30 to 50 words.
(iv) Section-C – question no. 27 to 33 are short answer type questions, carrying 3 marks each.
Answers to these questions should in the range of 50 to 80 words. :
(v) Section—D – question no. – 34 to 36 are long answer type questions carrying 5 marks each. Answer to these questions should be in the range of 80 to 120 words.
(vi) There is no overall choice. However, internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions.
(vii) Wherever necessary, neat and properly labelled diagrams should be drawn.

Section-A

1. What is the radius of curvature of a plane mirror?

2. Why is red colour selected for danger signal lights?

3. What is the cause of dispersion of light by prism.
OR
Why does the sky appear dark instead of blue to an astronaut?

4. Name the components of blood which transport:
(i) Food, carbon dioxide and nitrogeneous wastes
(ii) Oxygen

5. Write the relationship between heat energy produced in a conductor when potential difference V is applied across its terminals and a current, I flows through it for the time ‘F.

6. A beam of light is incident through the holes on side A and emerges out of the hole on the other face of the box as shown in the figure. What type of lens could be inside the box?

7. Why do stars twinkle?

8. A lens forms an image at Y of an object at X. Where does the lens form an image of an object at P?

9. What indication do we get by appearance of dwarf plant in F2 generation?
OR
What is sex of the baby that inherits Y-chromosome from the father?

10. If a women is using copper-T, will it help in protecting against sexually transmitted diseases?
OR
Why is temperature of scrotal sac 2°C less than the body temperature?

11. Name the intermediate and the end products of glucose breakdown on aerobic respiration.

In the experiment “Chlorophyll is necessary for photosynthesis’, why does the green part of variegated leaf turns blue black after putting in iodine solution?

12. Out of Li and K, which one have stronger metallic character and why?
OR
The formula of magnesium oxide is MgO. State the formula of barium nitrate and barium sulphate, if barium belongs to the same group.

13. X + YSO₄ → XSO₄ + Y
Y + XSO₄ → No reaction
Out of two elements, ‘X’ and ‘Y’ which is more reactive and why?

Assertion (A) and Reason (R)
For question numbers 14,15 and 16, two statements are given- one labeled Assertion (A) and the other labeled Reason (R). Select the correct answer to these questions from the codes (i), (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.

14. A. Copper sulphate solution turns blue litmus red.
R. Copper sulphate is salt of strong acid H₂SO₄, weak base Cu(OH)₂, therefore, acidic in nature.
Answer:
(i)

15. A. The angle of incidence and reflection are equal.
R. The angle between incidence ray and normal is called angle of incidence.
Answer:
(ii)

16.
R. It is a combination reaction because CO combines with H₂ to form CH₃OH i.e. two substances combine to form a single compound.
OR
1. The reaction, MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂ is an example of redox reaction.
2. In this reaction, HCl is reduced to Cl₂ whereas MnO₂ is oxidized to MnCl.
Answer:
(ii) OR (iii)

Answer Q. No 17 – 20 contain five sub-parts each. You are expected to answer any four sub­parts in these questions.

17. Read the following and answer any four questions from 17 (i) to 17 (v) (4 × 1 = 4)

The growing size of the human population is a cause of concern for all people. The rate of birth and death in a given population will determine its size. Reproduction is the process by which organisms increase their population. The process of sexual maturation for reproduction is gradual and takes place while general body growth is still going on.

Some degree of sexual maturation does not necessarily mean that the mind or body is ready for sexual acts or for having and bringing up children. Various contraceptive devices are being used by human beings to control the size of population.

(i) Which of the following is not a common sign of sexual maturation in boys and girls.
(a) Pubic hair
(b) Menstrual cycle in females
(c) Broad shoulders in females
(d) Wider chest in males
Answer:
(c) Broad shoulders in females

(ii) Which contraceptive method changes the hormonal balance of the body?
(a) Condoms
(b) Orals pills
(c) IUCD
(d) None of these
Answer:
(b) Orals pills

(iii) Sex ratio of females/1000 males in different states are as follows:

Name the state which improves the ratio to maximum extent in 2013-15.
(a) Delhi
(b) Haryana
(c) Uttar Pradesh
(d) Punjab
Answer:
(d) Punjab

(iv) According to the tabel in above question, which state declines this ratio to maximum extent in 2013-15.
(a) Delhi
(b) Haryana
(c) Uttar Pradesh
(d) Punjab
Answer:
(b) Haryana

(v) What is the major cause of less females than males in India?
(a) Males live longer than females
(b) Naturally, male child birth rate is higher than female child
(c) Female foeticide
(d) None of these
Answer:
(c) Female foeticide

18. Read the following and answer any four questions from 18 (i) to 18 (v) (4 × 1 = 4)
The data for four elements is given below:

(i) Name the element that is solid at room temperature.
(a) Carbon
(b) Nitrogen
(c) Fluorine
(d) Neon
Answer:
(a) Carbon

(ii) Why is the boiling point of carbon the highest?
(a) Carbon atoms linked through strong ionic bonds to form molecules.
(b) Carbon atoms are close together with strong covalent bonds.
(c) Carbon atoms are small in size thus have more stronger attractions among them.
(d) Carbon atoms are not linked to each other.
Answer:
(b) Carbon atoms are close together with strong covalent bonds.

(iii) Which of the following element is inert?
(a) Carbon
(b) Nitrogen
(c) Fluorine
(d) Neon
Answer:
(d) Neon

(iv) Carbon has many allotropes with macromolecular structure. Which of the following is not such kind of allotrope of carbon?
(a) Diamond
(b) Fullerene
(c) Graphite
(d) Coke
Answer:
(d) Coke

(v) Which of the following is the most reactive element?
(a) Carbon
(b) Nitrogen
(c) Fluorine
(d) Neon
Answer:
(c) Fluorine

19. Read the following and answer any four questions from 19 (i) to 19 (v) (4 × 1 = 4)

(i) What is the range of resistivity in metals which are conductor of electricity?
(a) 10^-8 to 10^-7 Ωm
(b) 10^-7 to 10^-6 Ωm
(c) 10 ⁸ to 10^-6 Qm
(d) 10 ⁸ to 10 ⁴ Qm
Answer:
(c) 10 ⁸ to 10^-6 Qm

(ii) Why are alloys used in heating devices like electric iron, toasters, immersion rods, etc.?
(1) Alloys have high resistivity.
(2) Alloys do not oxidise or bum at high temperature.
(3) Alloys have high conductivity thus allow high current through it
(a) III only
(b) I only
(c) II and III
(d) I and II
Answer:
(d) I and II

(iii) Which of the following is used in transmission wires?
(a) Cu
(b) Al
(c) Zn
(d) Fe
Answer:
(d) Fe

(iv) Which is the best conducting metal?
(a) Cu
(b) Ag
(c)  Au
(d) Hg
Answer:
(d) Hg

(v) Based on resistivity, which of the following is better to use as insulation to protect us from electric current.
(a) Glass
(b) Hard rubber
(c) Nichrome
(d) Diamond
Answer:
(c) Nichrome

20. Read the following and answer any four questions from 20 (i) to 20 (v)  (4 × 1 = 4)

When a single parent is involved in the formation of a new individual, without the fusion of gametes, it is called asexual reproduction. It involves repeated mitotic divisions.

Sexual reproduction is a process of combining DNA from two different individuals during reproduction. This is brought about by the fusion of the male and female gametes.

(i) The type of reproduction taking place is

(a) Budding
(b) Fragmentation
(c) Regeneration
(d) Fission
Answer:
(c) Regeneration

(ii) Choose the right option

Answer:
(c)

(iii) Where does fertilisation occur in human females?
(a) Uterus
(b) Cervix
(c) Oviduct
(d) None of these
Answer:
(d) None of these

(iv) The simple animals like Planaria can be cut into a number of pieces and each piece grows into a complex organism. What is the process known as?
(a) Budding
(b) Fragmentation
(c) Spore formation
(d) Regeneration
Answer:
(d) Regeneration

(v) Spirogyra reproduces by
(a) Fission
(b) Regeneration
(c) Fragmentation
(d) Budding
Answer:
(c) Fragmentation

Section-B

21. Identify the type of magnetic field represented by the magnetic field lines given below and name the type of conductors which can produce them.

22. The values of current I flowing in a given resistor for the corresponding values of potential difference V across the resistor are given below:

Plot a graph between V and I and calculate the resistance of that resistor.
Answer:
3.314 Ω

23. You have three test tubes. One of them contains distilled water and the other two contain an acidic and a basic solution, respectively. If you are given only red litmus paper; how will you identify the contents of each test tube?
OR
Equal lengths of magnesium ribbon are taken in test tubes ‘A’, and ‘B\ Hydrochloric acid (HCl) is added to test tube ‘A’ while acetic acid (CH₃COOH) is added to test tube ‘B\ In which test tube, will the fizzing occur more vigorously and why?

24. A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of reaction.

25. A ray of light incident on rectangular glass slab emerges parallel to itself. Draw a labelled diagram to justify this statement.
OR
Define absolute refractive index. Mention its unit. Can the value of absolute refractive index be smaller than 1 ? Justify your answer.

26. How does the metallic character of elements changes along a period of the periodic table from left to right and why?

Section – C

27. Show the path of the reflected ray, after reflection in each case.

(i) Draw a diagram of human alimentary canal and label on it:
Oesophagus, Gall bladder, Liver and Pancreas

(ii) Explain the statement, “Bile does not contain any enzyme, but it is essential for digestion.”
OR
How respiration does takes place in plants?

29. Based on the group valency of elements, state the formula of the following, giving justification for each.
(i) Oxides of Group 1 elements.
(ii) Halides of the elements of Group 13.
(iii) Compounds formed when an element of group 2 combines with an element of Group 16.

30. A magnetic compass needle is placed in the plane of paper near point A as shown in the figure. In which plane should a straight current carrying conductor be placed so that it passes through A and there is no change in the “A deflection of the compass? Under what conditions is the deflection maximum and why?

31. (i) What is the nature of food coming from stomach?
(ii) Mention any two structural modifications in small intestine which helps in absorption of food.

32. An electron enters a magnetic field, at right angle to the field direction.
(i) State the rule to find the direction of force acting on the electron.

(ii) What will be the direction of force acting on the electron, in the above case?

33. (i) Two conductors A & B of resistance 5 ohms and 10 ohms respectively can be arranged in parallel and later on in series. In each arrangement, the total voltage applied is 120V. In which arrangement will the voltage across A and B be the same and in which case will the current flowing through A and B be the same?
(ii) Calculate the total resistance of each arrangement.
Answer:
(ii) (a) 3.33Ω
(b) 15Ω

Section-D

34. The structural formula of five compounds are given below.

(i) Which two compounds belong to the same homologous series?
(ii) Which compound belongs to the same homologous series as ethanol?
(iii) Which compound on hydrogenation produces E?
(iv) Which compound when dissolved in water turns blue litmus red?
(v) Name the homologous series for compound B.

35. (i) Identity A, B, C and D in the given diagram and write their names.

(ii) What is pollination? Explain its significance.
(iii) Explain the process of fertilisation in flowers. Name the parts of the flower that develop after fertilisation into
(a) seed
(b) fruit
OR
(i) Draw the diagram of female reproductive system and match and mark the part (s):
(a) Where block is created surgically to prevent fertilisation.
(b) Where CuT is inserted.
(c) Inside which condom can be placed.
(ii) Why do more and more people prefer to use condoms? What is the principle behind use of condoms?

36. (i) Name the organisms which belong to first and third trophic level in food chain comprising of the following:
Insects, birds, frog and grass.
(ii) What will happen if we kill all the organisms in one trophic level?
OR
(i) Give reason to justify the following:
(a) The existence of decomposers is essential in a biosphere.
(b) Flow of energy in a food chain is unidirectional.
(ii) Why is improper disposal of waste a curse to environment?

Students can access the CBSE Sample Papers for Class 10 Science with Solutions and marking scheme Set 3 will help students in understanding the difficulty level of the exam.

CBSE Sample Papers for Class 10 Science Set 3 with Solutions

Time: 3 Hours
Maximum Marks: 80

General Instructions:

(i) The question paper comprises four sections A, B, C and D. There are 36 questions in the question paper. All questions are compulsory.
(ii) Section-A – question no. 1 to 20 – all questions and parts there of are of one mark each.
These questions contain multiple choice questions (MCQs), very short answer questions and assertion – reason type questions. Answers to these should be given in one word or one sentence.
(iii) Section-B – question no. 21 to 26 are short answer type questions, carrying 2 marks each. Answers to these questions should in the range of 30 to 50 words.
(iv) Section-C – question no. 27 to 33 are short answer type questions, carrying 3 marks each.
Answers to these questions should in the range of 50 to 80 words. :
(v) Section—D – question no. – 34 to 36 are long answer type questions carrying 5 marks each. Answer to these questions should be in the range of 80 to 120 words.
(vi) There is no overall choice. However, internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions.
(vii) Wherever necessary, neat and properly labelled diagrams should be drawn.

Section – A

Question 1.
Name a cyclic unsaturated carbon compound.
Answer:
Cyclopentene / Cyclohexene-formula or structure (or any other).

Question 2.
The change in magnetic field lines in a coil is the cause of induced electric current in it. Name the underlying phenomenon.
Answer:
Electromagnetic Induction

Question 3.
Why do we store silver chloride in dark coloured bottles?
Answer:
It is because it undergoes photochemical decomposition reaction in the presence of sunlight.

Question 4.
How many male gametes are produced by pollen grains?
Answer:
Two

Question 5.
Two beakers with chemicals are shown below. Name the beaker which will show exothermic reaction and the one which will be endothermic in nature.

Answer:
Exothermic : Beaker A
Endothermic : Beaker B

Question 6.
What will happen, if a solution of sodium hydrogen carbonate is heated? Give the equation of the reaction involved.
OR
How chloride of lime differs chemically from calcium chloride?
Answer:
Sodium carbonate, carbon dioxide and water will be formed.
\(2 \mathrm{NaHCO}_{3}(\mathrm{~s}) \stackrel{\text { Heat }}{\longrightarrow} \mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{~s})+\mathrm{CO}_{2}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O} \text { ( } \mathrm{l}\)

Question 11.
What will happen to a plant if its xylem is removed?
OR
Why is it advisable to breathe through nose?
Answer:
If xylem is removed from a plant, transport of water and nutrients will stop and plant will die.
OR
There are fine hair and mucus gland in the inner lining of nose which can filter the incoming air from germs and dust. Moreover, the air attains the optimum temperature before reaching the lungs.

Question 12.
An element ‘X’ on reacting with oxygen forms an oxide X₂O. This oxide dissolves in water and turns blue litmus red. State whether ‘X’ is metal or non-metal.
Answer:
Non-metal

Question 13.
What is the speed of blue light travelling in vacuum?
Answer:
The speed of blue light is same as that of light i.e. 3 x 10⁸ m s^–1.
Assertion (A) and Reason (R)
For question numbers 14,15 and 16, two statements are given- one labeled Assertion (A) and the other labeled Reason (R). Select the correct answer to these questions from the codes (i), (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.

Question 14.
A. The element carbon forms the basic structural framework of more compounds than any other element.
R. The carbon-carbon bond is ionic.
Answer:
(iii)

Question 15.
A. Pollination is different from fertilisation.
R. The process of transfer of pollens from anther to stigma is called pollination which takes place in plants.
Answer:
(iv)

Question 16.
A. A 200 W bulb glows with more brightness than 100 W bulb.
R. 100 W bulb has more resistance than 200 W bulb.
OR
A. When two resistances of 4Ω are connected in series, total resistance is 8Ω.
B. When two resistances of 4Ω are connected in parallel total resistance is 2Ω.
Answer:
(i) OR (ii)

Answer Q. No 17 – 20 contain five sub-parts each. You are expected to answer any four sub­parts in these questions.

Question 17.
Read the following and answer any four questions from 17 (i) to 17 (v) (4 × 1 = 4)

The growing size of the human population is a cause of concern for all people. The rate of birth and death in a given population will determine its size. Reproduction is the process by which organisms increase their population. The process of sexual maturation for reproduction is gradual and takes place while general body growth is still going on. Some degree of sexual

chemicals are not biodegradable, they get accumulated progressively at each trophic level. The maximum concentration of these chemicals gets accumulated in our bodies and greatly affects the health of our mind and body.

(i) Why is the maximum concentration of pesticides found in human beings?
(a) Humans are at the top level in any food chain
(b) Major part of crops cultivated using pesticides are consumed by humans
(c) Pesticides are stored in different organs of humans
(d) None of these
Answer:
(a) Humans are at the top level in any food chain

(ii) Which method could be applied to reduce our intake of pesticides through food to some extent.
(a) Washing crops thoroughly
(b) Organic fanning
(c) Use of bio-pesticides
(d) All of these
Answer:
(d) All of these

(iii) Various steps in a food chain represent:
(a) Food web
(b) Trophic level
(c) Ecosystem
(d) Biomagnification
Answer:
(b) Trophic level

(iv) With regard to various food chains operating in an ecosystem, man is a:
(a) Consumer
(b) Producer
(c) Producer and consumer
(d) Producer and decomposer
Answer:
(a) Consumer

(v) Food web is constituted by
(a) relationship between the organisms and the environment.
(b) relationship between plants and animals.
(c) various interlinked food chains in an ecosystem.
(d) relationship between animals and environment
Answer:
(c) various interlinked food chains in an ecosystem.

Question 19.
Read the following and answer any four questions from 19 (i) to 19 (v) (4 × 1 = 4)

Electrical resistivity and its inverse, electrical conductivity are fundamental properties of a material that quantifies how strongly it resists or conducts electric current. A low resistivity indicates a material that readily allows electric current to flow.

Resistance is defined as the ratio of potential difference across a conductor to the current passing through it. Resistance is the property of a conductor to resist the flow of charges through it.

Both resistance and resistivity describe how difficult it is to G make electrical current flow through a material, but unlike w resistance, resistivity is an intrinsic property. This means that g all pure copper wires irrespective of their shape and size, have the same resistivity, but a long, thin copper wire has a much larger resistance than a thick, short copper wire. Every material has its own characteristic resistivity. For example, rubber has a far larger resistivity than copper. The resistivity of metals also varies with temperature.

The resistance of almost all alloys increases with increase in temperature but the rate of change of resistance is less than that of metals. In fact, the resistance of certain alloys such as Manganin, Eureka and Constantan show practically no change in resistance to a considerable range of temperature.                        ‘

(i) What happens to the resistivity of a wire if it is stretched?
(a) It will increase
(b) It will decrease
(c) First increases then decreases
(d) Remains the same
Answer:
(d) Remains the same

(ii) Though silver is a good conductor, why it is not an ideal choice for transmission of electricity?
1. It is expensive
2. It oxidizes and tarnishes when it comes in contact with air
3. Its resistivity decreases with increase in temperature
(a) Only 1
(b) Only 2
(c) Both 1 and 2
(d) Only 3
Answer:
(c) Both 1 and 2

(iii) The area of cross section of a wire becomes half when its length is stretched to double. How the resistance of the wire is affected in the new condition?
(a) Resistance of the wire remains unchanged
(b) Resistance of the wire decreases to half
(c) Resistance of the wire increases to double
(d) Resistance of the wire increases four times
Answer:
(d) Volume of the wire remains the same before and after stretching. Assuming wire to be cylindrical in shows them  volume = Area of base x height/length
Due to stretching if length is increased, area will decrease.
R = ρl/A
New length = 2l
New area = A/2
Resistance increases four times.

(iv) If there are two wires, W₁ and W₂ of same material and same length but have radius r and 2r respectively, then which wire will have more resistance?
(a) Wire W₁ has more resistance as compare to W₂
(b) Wire W₂ has more resistance as compare to W₁
(c) Both the wires have same resistance
(d) Wire W₂ has three times resistance than wire W₁
Answer:
(a) Wire W₁ has more resistance as compare to W₂

(v) Ajay made the following conclusions regarding resistance of metals/alloy. Which one would you disagree with?
(a) The resistivity of a metal decreases with temperature
(b) A thick copper wire has less resistance than a thin copper wire of the same length
(c) Alloys are often used in the manufacture of standard resistors
(d) Low resistivity means the material easily allow the flow of electric current
Answer:
(a) The resistivity of a metal decreases with temperature

Question 20.
Read the following and answer any four questions from 20 (i) to 20 (v) (4 × 1 = 4)
The following graph shows the volume of hydrogen collected in four different experiments when dil. hydrochloric acid was reacted with zinc, copper, magnesium and iron metal.

(i) Name the graph that produces hydrogen gas faster.
(a) Graph 1
(b) Graph 2
(c) Graph 3
(d) Graph 4
Answer:
(d) Graph 4

(ii) Name the metal used in experiment that gave the result for graph-4.
(a) Mg
(b) Zn
(c) Fe
(d) Cu
Answer:
(a) Mg

(iii) Ways to speed up the slow reaction are
1. heating the reactants
2. cooling the reactants
3. using more diluted acid
4. using more concentrated acid
(a) 1 only
(b) 1 and 4
(c) 1 and 3
(d) 2 and 4
Answer:
(b) 1 and 4

(iv) The amount of zinc metal used for the above reaction is same but the concentration of acid is changed, what would be the effect on the rate of reaction?
(a) no change
(b) the speed will increase
(c) the speed will decrease
(d) the information is incomplete
Answer:
(d) the information is incomplete

(v) Which of the following metal liberates hydrogen gas on reaction with dilute HNO₃.
(a) Zn
(b) Cu
(c) Mg
(d) Fe
Answer:
(c) Mg

Section – B

Question 21.
The period 3 oxides are given below.
[Na₂O, MgO] [Al₂O₃]……………………. [SO₂, Cl₂O]
A                               B                                           C
State 2 characters of these oxides grouped as A & C
Answer:
Oxide A: Na₂O, MgO are basic in nature and ionic Oxide C : SO₂, Cl₂O are acidic in nature and covalent

Question 22.
Name two human organs that perform dual function and explain their functions to justify their dual nature.
Answer:
Two human organs with dual nature are pancreas and gonads. Pancreas secretes insulin hormone and digestive enzymes like trypsin ( pancreatic enzyme) similarly human gonads like testis and ovaries secretes the gametes like sperms and ovum respectively along with the sex hormones.

Question 23.
Why are small number of surviving tigers a cause of worry from genetics point of view?
Answer:
(i) Tigers may get extinct in near future due to natural calamities, lack of available food and due to their small number.
(ii) Cross breeding may be less possible. Variations will not occur, which is essential for the survival.
(iii) Adaptation due to changing environment, like cutting of forests, global warming becomes difficult.
(iv) Protection from enemies is easy if they are more in number.

Question 24.
An object is placed at a distance of 15 cm from a concave lens of focal length 30 cm. List four characteristics (nature, position, etc.) of the image formed by the lens.
Answer:

The image will be formed at 10 cm from ‘O’ on the same side as the object. It will be virtual, erect and diminished.

Question 25.
Write chemical equation for the reaction when
(i) Steam acts on red hot iron.
(ii) Zinc is added to iron(II) sulphate solution.
OR
State two reasons for the following facts:
(i) Sulphur is a non-metal.
(ii) Magnesium is a metal.
One of the reason must be supported with a chemical equation.
Answer:
(i) \(3 \mathrm{Fe}(s)+4 \mathrm{H}_{2} \mathrm{O}(g) \underset{\text { steam }}{\longrightarrow} \mathrm{Fe}_{3} \mathrm{O}_{4}(s)+4 \mathrm{H}_{2}(g)\)
(ii) Zn(s) + FeSO₄(aq) → ZnSO₄(aq) + Fe(s)
OR
(i) Sulphur is a poor conductor of electricity.
It reacts with oxygen to form SO₂ which forms acidic solution in water.
S + O₂ → S0_2
SO2 + H₂O →H₂SO₃

(ii) Magnesium is a metal because it is a good conductor of electricity.
It forms basic oxide with oxygen
\(2 \mathrm{Mg}+\mathrm{O}_{2} \stackrel{\text { Burning }}{\longrightarrow} 2 \mathrm{MgO}\)
\(\mathrm{MgO}+\underset{(\mathrm{Hot})}{\mathrm{H}_{2} \mathrm{O}} \rightarrow \underset{(\text { Base })}{\mathrm{Mg}(\mathrm{OH})_{2}}\)

Question 26.
Study the following circuit and answer the questions that follows:

(i) How much current is flowing through
(a) 10 Q and
(b) 15 Q resistor?
(ii) What is the ammeter reading?
OR
Find the current drawn from the battery by the network of four resistors shown in the figure.

Answer:
(i) Current through

Question 27.
1 g of copper powder was taken in a China dish and heated. What change takes place on heating? When hydrogen gas is passed over this heated substance, a visible change is seen in it. Give the chemical equations of reactions, the name and the color of the products formed in each case.
Answer:
A black colour is formed on the surface

Original/brown colour is restored

Question 28.
List the important products of the Chlor-alkali process. Write one important use of each.
OR
How is washing soda prepared from sodium carbonate? Give its chemical equation. State the type of this salt. Name the type of hardness of water which can be removed by it?
Answer:
Products: Hydrogen, Chlorine, Sodium hydroxide Uses:
Hydrogen: In the production of margarine/ammonia/as a fuel
Chlorine: Water treatment / swimming pools / production of PVC / Disinfectants / CFCs / Pesticides
Sodium hydroxide: For degreasing metal surface / in making soaps and detergents / paper making / artificial fibres.
OR
1. By recrystallisation of sodium carbonate
2. Na₂CO₃ + 10H₂O → Na₂CO₃.10H₂O
3. Basic Salt
4. Permanent hardness

Question 29.
Study the following cross showing self pollination in F₁, fill in the blank and answer the question that follow:

What are the combinations of character in the F₂ progeny? What are their ratios?
Answer:
F₁ progeny is Rr Yy-Round, Yellow
Combinations of character in the F₂ progeny are:

• Round yellow — 9 (Both dominant traits)
• Round green — 3 (One recessive, one dominant)
• Wrinkled yellow — 3 (One dominant, one recessive)
• Wrinkled green — 1 (both recessive traits)

The ratio is 9 : 3 : 3 : 1

Question 30.
Define the term pollination. Differentiate between self pollination and cross pollination. What is the significance of pollination?
Answer:
Pollination is the transfer of pollen from another to stigma.

• Pollination leads to fertilization resulting in the formation of zygote.

Question 31.
Why is Tyndall effect shown by colloidal particles? State four instances of observing the Tyndall effect.
Answer:
Because of the scattering of light.
Instances:

• When a fine beam of light enters a smoke-filled dark room through a small hole.
• When sunlight passes through a canopy of dense forest in foggy/ misty conditions.
• Blue colour of sky.
• Red colour of the sun during sunrise or sunset.

Question 32.
A V-I graph for a nichrome wire is given below. What do you infer from this graph? Draw a labelled circuit diagram to obtain such a graph.

Answer:
V α I or Potential difference is directly proportional to current

Note: If circuit diagram is correct but labelling of ammeter and voltmeter are incorrect, deduct 1 mark.

Question 33.
(i) Write the mathematical expression for Joule’s law of heating.
(ii) Compute the heat generated while transferring 96000 coulombs of charge in two hours through a potential difference of 40 V.
Answer:
(i) H = I²Ri
(ii) H = V.I.t = V.Q
Given:     V = 40 volts, Q = 96000 C
H = 40 V x 96000 C
= 3.84 x 10⁶ J

Section – D

Question 34.
The position of certain elements in the Modem Periodic Table are shown below.

Using the above table answer the following questions giving reasons in each case:
(i) Which element will form only covalent compounds?
(ii) Which element is a non-metal with valency 2?
(iii) Which element is a metal with valency 2?
(iv) Out of H, C and F which has largest atomic size?
(v) To which family does H, C and F belong?
OR
Define atomic size. Give its unit of measurement. In the modem periodic table what trend is observed in the atomic radius in a group and a period and why is it so?
Answer:
(i) E, it has 4 valence electrons.
(ii) B, it needs only 2 electrons to attain stable configuration.
(iii) D, it loses two electrons to attain stable configuration.
(iv) F, it has the largest size since size increases down the group.
(v) Noble gases, outermost shell is complete.
OR

• Atomic size is the distance between the centre of the nucleus and the outermost shell of an isolated atom.
• Picometer /pm
• Trends in Atomic radius
  In a group: increases down the group; due to addition of a new shell.
  In a period: atomic radius decreases from left to right; due to increase in pulling power of nucleus / due to addition of electrons in the same shell.

Question 35.
(i) What is the law of dominance of traits? Explain with an example.
(ii) Why are the traits acquired during the life time of an individual not inherited? Explain.
Answer:
(i) Law of dominance of traits: In a cross between a pair of contrasting characters, only one parental character will be expressed in F₁ generation which is called dominant trait and the other is called a recessive trait.
For example – in pea plants.

All plants in F₁ generation were tall proving that the gene for tallness is dominant over the gene for dwarfness/short, which is not able to express itself in the presence of dominant trait.

(ii) Traits acquired by an organism during its lifetime are known as aquired traits. These traits are not inherited because they occur in somatic cells only/do not cause any change in the DNA of the germ cells.

Question 36.
Draw a ray diagram in each of the following cases to show the formation of image, when the object is placed:
(i) between optical centre and principal focus of a convex lens.
(ii) anywhere in front of a concave lens.
(iii) at 2F of convex lens.
State the signs and values of magnifications in the above mentioned cases (i) and (ii).
OR
An object 4.0 cm in size, is placed 25.0 cm in front of a concave mirror of focal length 15.0 cm.
(i) At what distance from the mirror should a screen be placed in order to obtain a sharp image?
(ii) Find the size of the image.
(iii) Draw a ray diagram to show the formation of image in this case.
Answer:

Students can access the CBSE Sample Papers for Class 10 Science with Solutions and marking scheme Set 2 will help students in understanding the difficulty level of the exam.

CBSE Sample Papers for Class 10 Science Set 2 with Solutions

Time: 3 Hours
Maximum Marks: 80

General Instructions:

(i) The question paper comprises four sections A, B, C and D. There are 36 questions in the question paper. All questions are compulsory.
(ii) Section-A – question no. 1 to 20 – all questions and parts there of are of one mark each.
These questions contain multiple choice questions (MCQs), very short answer questions and assertion – reason type questions. Answers to these should be given in one word or one sentence.
(iii) Section-B – question no. 21 to 26 are short answer type questions, carrying 2 marks each. Answers to these questions should in the range of 30 to 50 words.
(iv) Section-C – question no. 27 to 33 are short answer type questions, carrying 3 marks each.
Answers to these questions should in the range of 50 to 80 words. :
(v) Section—D – question no. – 34 to 36 are long answer type questions carrying 5 marks each. Answer to these questions should be in the range of 80 to 120 words.
(vi) There is no overall choice. However, internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions.
(vii) Wherever necessary, neat and properly labelled diagrams should be drawn.

Section-A

Question 1.
List any two observations when ferrous sulphate is heated in a dry test tube?
OR
Identify the products formed when 1 mL of dil. hydrochloric acid is added to 1g of sodium metal?
Answer:

• Initial light green colour changes to reddish-brown colour
• Colourless gas is evolved
• Gas with choking smell is evolved (Any two)
  OR
• Sodium chloride and hydrogen gas

Question 2.
Write the chemical name and chemical formula of the salt used to remove the permanent hardness of water.
Answer:
Sodium carbonate decahydrate, Na₂CO₃.10H₂O

Question 3.
Which of the following is not observed in a homologous series? Give reason for your choice,
(a) Change in chemical properties
(b) Difference in -CH₂ and 14u molecular mass
(c) Gradation in physical properties
(d) Same functional group
Answer:
(a) It does not occur due to the presence of the same functional group.

Question 4.
Why does the sun appear white at noon?
Answer:
The light is least scattered at noon.

Question 5.
Both a spherical mirror and a thin spherical lens have a focal length of (-)15 cm. What type of mirror and lens are these?
Answer:
Both are concave.
Alternative answer that should be given credit: Plano-concave lens.

Question 6.
The image formed by a concave mirror is observed to be real, inverted and larger than the object. Where is the object placed?
OR
Name the part of a lens through which a ray of light passes without suffering any deviation.
Answer:
Between the principal focus and the centre of curvature.
OR
Optical centre.

Question 7.
In the arrangement shown in figure there are two coils wound on a nonconducting cylindrical rod. Initially the key is not inserted in the circuit. Later the key is inserted and then removed shortly after.

What are the two observations that can be noted from the galvanometer reading?
Answer:
There are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions.

Question 8.
Draw the magnetic field lines around a straight current carrying conductor.
Answer:
The field consists of concentric circles centred on the wire

Question 9.
Two unequal resistances are connected in parallel. If you are not provided with any other parameters (eg. numerical values of I and R), what can be said about the voltage drop across the two resistors?
OR
Some work is done to move a charge Q from infinity to a point A in space. The potential of the point A is given as V. What is the work done to move this charge from infinity in terms of Q and V?
Answer:
Voltage-drop is same across both OR W = QV

Question 10.
Veins are thin walled and have valves. Justify.
Answer:
Veins have thin walls because the blood there is no longer under pressure and they have valves to ensure blood flow in one direction.

Question 11.
How is the wall of small intestine adapted for performing the function of absorption of food?
OR
Out of a goat and a tiger, which one will have a longer small intestine? Justify your answer.
Answer:
The inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption.
OR
Goat because herbivores eating grass need a longer small intestine to allow the cellulose to be digested.

Question 12.
Explain how ozone being a deadly poison can still perform an essential function for our environment.
OR
Give reason why a food chain cannot have more than four trophic levels.
Answer:
Ozone layer protects us from harmful effects of UV radiation.
OR
The loss of energy at each step is so great that very little usable energy remains after four trophic levels.

Question 13.
State the role of pancreas in digestion of food.
Assertion (A) and Reason (R)
For question numbers 14,15 and 16, two statements are given- one labeled Assertion (A) and the other labeled 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.
Answer:
The pancreas secretes digestive juice which contains enzymes like trypsin for digesting proteins and lipase for breakdown of emulsified fats.

Question 14.
A. After white washing the walls, a shiny white finish on walls is obtained after two to three days. R. Calcium oxide reacts with carbon dioxide to form calcium hydrogen carbonate which gives a shiny white finish.
Answer:
(iii)

Question 15.
A. Food chain is responsible for the entry of harmful chemicals in our bodies. R. The length and complexity of food chains vary greatly.
OR
A. Greater number of individuals are present in lower trophic levels.
R. The flow of energy is unidirectional.
Answer:
(ii) OR (ii)

Question 16.
A. A geneticist crossed a pea plant having violet flowers with a pea plant with white flowers, he got all violet flowers in first generation. R. White colour gene is not passed on to next generation.
Answer:
(i)

Answer Q. No 17 – 20 contain five sub-parts each. You are expected to answer any four sub¬parts in these questions.

Question 17.
Read the following and answer any four questions from 17 (i) to 17 (v) (4 x 1 = 4)
All living cells require energy for various activities. This energy is available by the breakdown of simple carbohydrates either using oxygen or without using oxygen. 4 x 1 = 4
(i) Energy in the case of higher plants and animals is obtained by
(a) Breathing
(b) Tissue respiration
(c) Organ respiration
(d) Digestion of food
Answer:
(b) Tissue respiration

(ii) The graph below represents the blood lactic acid concentration of an athlete during a race of 400 m and shows a peak at point D. Respiration in athletics: The blood of an athlete was tested before, during and after a 400 m race:

Lactic acid production has occurred in the athlete while running in the 400 m race. Which of the following processes explains this event?
(a) Aerobic respiration
(b) Anaerobic respiration
(c) Fermentation
(d) Breathing
Answer:
(b) Anaerobic respiration

(iii) Study the graph below that represents the amount of energy supplied with respect to the time while an athlete is running at full speed.

Choose the correct combination of plots and justification provided in the following table.

Answer:
(b)

(iv) The characteristic processes observed in anaerobic respiration are
(1) presence of oxygen
(2) release of carbon dioxide
(3) release of energy
(4) release of lactic acid
(a) (1), (2) only
(b) (1), (2), (3) only
(c) (2), (3), (4) only
(d) (4) only
Answer:
(c) (2), (3), (4) only

(v) Study the table below and select the row that has the incorrect information.

Answer:
(d)

Question 18.
Read the following and answer any four questions from 18 (i) to 18 (v). (4 x 1 = 4)
Answer:
Metallic Character
The ability of an atom to donate electrons and form positive ion (cation) is known as electropositivity or metallic character. Down the group, metallic character increases due to increase in atomic size and across the period, from left to right electropositivity decreases due to decrease in atomic size.

Non-Metallic Character
The ability of an atom to accept electrons to form a negative ion (anion) is called non-metallic character or electronegativity. The elements having high electronegativity have a higher S tendency to gain electrons and form anion. Down the group, electronegativity decreases due to increase in atomic size and across the period, from left to S right electronegativity increases due to decrease in atomic size.

(i) Which of the following correctly represents the decreasing order of metallic character of alkali metals plotted in the graph?

(a) Cs > Rb > Li > Na > K
(b) K > Rb > Li > Na > Cs
(c) Cs > Rb > K > Na > Li
(d) Cs > K > Rb > Na > Li
Answer:
(c) Cs > Rb > K > Na > Li

(ii) Hydrogen is placed along with alkali metals in the modem periodic table though it shows non-metallic character
(a) as hydrogen has one electron & readily loses electron to form negative ion
(b) as hydrogen can easily lose one electron like alkali metals to form positive ion
(c) as hydrogen can gain one electron easily like halogens to form negative ion
(d) as hydrogen shows the properties of non-metals
Answer:
(b) as hydrogen can easily lose one electron like alkali metals to form positive ion

(iii) Which of the following has highest electronegativity?
(a) F
(b) Cl
(c) Br
(d) I
Answer:
(a) F

(iv) Identify the reason for the gradual change in electronegativity in halogens down the group.
(a) Electronegativity increases down the group due to decrease in atomic size
(b) Electronegativity decreases down the group due to decrease in tendency to lose electrons
(c) Electronegativity decreases down the group due to increase in atomic radius/ tendency to gain electron decreases
(d) Electronegativity increases down the group due to increase in forces of attractions between nucleus & valence electrons
Answer:
(c) Electronegativity decreases down the group due to increase in atomic radius/ tendency to gain electron decreases

(v) Which of the following reason correctly justifies that “Fluorine (72pm) has smaller atomic radius than Lithium (152pm)”?
(a) F and Li are in the same group. Atomic size increases down the group
(b) F and Li are in the same period. Atomic size increases across the period due to increase in number of shells
(c) F and Li are in the same group. Atomic size decreases down the group
(d) F and Li are in the same period and across the period atomic size/radius decreases from left to right.
Answer:
(a) F and Li are in the same group. Atomic size increases down the group

Question 19.
Read the following and answer any four questions from 19 (1) to 19 (v). (4 x 1 = 4)
Sumati wanted to see the stars of the night sky. She knows that she needs a telescope to see those distant stars. She finds out that the telescopes, which are made of lenses, are called refracting telescopes and the ones which are made of mirrors are called reflecting telescopes.

So she decided to make a refracting telescope. She bought two lenses, Lj and L2. out of which Lj was bigger and L2 was smaller. The larger lens gathers and bends the light, while the smaller lens magnifies the image. Big, thick lenses are more powerful. So to see far away, she needed a big powerful lens.

Unfortunately, she realized that a big lens is very heavy. Heavy lenses are hard to make and difficult to hold in the right place. Also since the light is passing through the lens, the surface of the lens has to be extremely smooth. Any flaws in the lens will change the image. It would be like looking through a dirty window.

(i) Based on the diagram shown, what kind of lenses would Sumati need to make the telescope?
(a) Concave lenses
(b) Convex lenses
(c) Bifocal lenses
(d) Flat lenses

(ii) If the powers of the lenses L₁ and L₂ are in the ratio of 4:1, what would be the ratio of the focal length of L₁ and L₂?
(a) 4:1
(b) 1:4
(c) 2:1
(d) 1:1

(iii) What is the formula for magnification obtained with a lens?
(a) Ratio of height of image to height of object
(b) Double the focal length.
(c) Inverse of the radius of curvature.
(d) Inverse of the object distance.

(iv) Sumati did some preliminary experiment with the lenses and found out that the magnification of the eyepiece (L₂) is 3. If in her experiment with L₂ she found an image at 24 cm from the lens, at what distance did she put the object?
(a) 72 cm
(b) 12 cm
(c) 8 cm
(d) 6 cm

(v) Sumati bought not-so-thick lenses for the telescope and polished them. What advantages, if any, would she have with her choice of lenses?
(a) She will not have any advantage as even thicker lenses would give clearer images.
(b) Thicker lenses would have made the telescope easier to handle.
(c) Not-so-thick lenses would not make the telescope very heavy and also allow considerable amount of light to pass.
(d) Not-so-thick lenses will give her more magnification.
Answer:

Question 20.
Read the following and answer any four questions from 20 (i) to 20 (v). (4 x 1 = 4)
A solenoid is a long helical coil of wire through which a current is run in order to create a magnetic field. The magnetic field of the solenoid is the superposition of the fields due to the current through each coil.

It is nearly uniform inside the solenoid and close to zero outside and is similar to the field of a bar magnet having a north pole at one end and a south pole at the other depending upon the direction of current flow. The magnetic field produced in the solenoid is dependent on a few factors such as, the current in the coil, number of turns per unit length etc.

The following graph is obtained by a researcher while doing an experiment to see the variation of the magnetic field with respect to the current in the solenoid.

The unit of magnetic field as given in the graph attached is in milli-Tesla (mT) and the current is given in Ampere.

(i) What type of energy conversion is observed in a linear solenoid?
(a) Mechanical to Magnetic
(b) Electrical to Magnetic
(c) Electrical to Mechanical
(d) Magnetic to Mechanical
Answer:
(c) Electrical to Mechanical

(ii) What will happen if a soft iron bar is placed inside the solenoid?
(a) The bar will be electrocuted resulting in short-circuit.
(b) The bar will be magnetised as long as there is current in the circuit.
(c) The bar will be magnetised permanently.
(d) The bar will not be affected by any means.
Answer:
(b) The bar will be magnetised as long as there is current in the circuit.

(iii) The magnetic field lines produced inside the solenoid are similar to that of…
(a) a bar magnet
(b) a straight current carrying conductor
(c) a circular current carrying loop
(d) electromagnet of any shape
Answer:
(a) a bar magnet

(iv) After analysing the graph a student writes the following statements.
I. The magnetic field produced by the solenoid is inversely proportional to the current.
II. The magnetic field produced by the solenoid is directly proportional to the current.
III. The magnetic field produced by the solenoid is directly proportional to square of the current.
IV. The magnetic field produced by the solenoid is independent of the current.
Choose from the following which of the following would be the correct statement(s).
(a) Only IV
(b) I and III and IV
(c) I and II
(d) Only II
Answer:
(d) Only II

(v) From the graph deduce which of the following statements is correct.
(a) For a current of 0.8 A the magnetic field is 13 mT
(b) For larger currents, the magnetic field increases non-linearly.
(c) For a current of 0.8A the magnetic field is 1.3 mT
(d) There is not enough information to find the magnetic field corresponding to 0.8A current.
Answer:
(a) For a current of 0.8 A the magnetic field is 13 mT

Section-B

Question 21.
Bile juice does not have any digestive enzyme but still plays a significant role in the process of digestion. Justify the statement.
OR
In birds and mammals the left and right side of the heart are separated. Give reasons.
Answer:
Bile juice makes the acidic food coming from the stomach alkaline for the action of pancreatic enzymes. Bile salts break the large globules of fat in the intestine to smaller globules increasing the efficiency of enzyme action. This is similar to the emulsifying action of soaps on dirt.
OR
The separation keeps oxygenated and deoxygenated blood from mixing allowing a highly efficient supply of oxygen to the body. This is useful in animals that have high energy needs (birds and mammals) which constantly use energy to maintain their body temperature.

Question 22.
State the events occurring during the process of photosynthesis. Is it essential that these steps take place one after the other immediately?
Answer:

Absorption of light energy by chlorophyll.

• Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
• Reduction of carbon dioxide to carbohydrates.

These steps need not take place one after the other immediately. For example, desert plants take up carbon dioxide at night and prepare an intermediate which is acted upon by the energy absorbed by the chlorophyll during the day

Question 23.
Give a test that can be used to confirm the presence of carbon in a compound. With a valency of 4, how is carbon able to attain noble gas configuration in its compounds?
OR
The number of carbon compounds is more than those formed by all other elements put together. Justify the statement by giving two reasons.
Answer:
A bum compound in air/ oxygen; Gas evolved turns lime water milky
By sharing its four valence electrons with other elements.
OR

• Due to self linking ability of carbon/catenation
• Since carbon has a valency of four it can form bonds with four other atoms of carbon or atoms of some other mono-valent element.
• Due to small size of carbon it forms very strong and (or) stable bonds with other elements

Question 24.
The following observations were made by a student on treating four metals P, Q, R and S with the given salt solutions:

Based on the above observations:
(i) Arrange the given samples in the increasing order of reactivity
(ii) Write the chemical formulae of products formed when Q reacts with CuS04 solution.
Answer:
(i) S > R > P > Q
(ii) Cu and QSO₄

Question 25.
A student observes the given phenomenon in the lab as a white light passes through a prism. Among many other colours, he observed the position of the two colours red and violet. What is the phenomenon called? What is the reason for the violet light to bend more than the red light?

Answer:

• The phenomenon is called dispersion.
• Speed of violet light inside the prism is slowest and that of red is highest. Hence, the deviation of violet light is maximum and that of red is minimum.

Question 26.
A student has two resistors- 2 Q and 3 Q. She has to put one of them in place of R2 as shown in the circuit. The current that she needs in the entire circuit is exactly 9A. Show by calculation which of the two resistors she should choose.

Answer:
The overall current needed = 9A. The voltage is 12V Hence by Ohm’s law V=IR,
R₂ = 2Q
The resistance for the entire circuit = \(=\frac{12}{9}=\frac{4}{3} \Omega=\mathrm{R}\)
R₁ and R₂ are in parallel.
Hence, R = \(R=\frac{\left(R_{1} R_{2}\right)}{\left(R_{1}+R_{2}\right)}=\frac{4 R_{2}}{\left(4+R_{2}\right)}=\frac{4}{3}\)

Section-C

Question 27.
After self-pollination in pea plants with round, yellow seeds, following types of seeds were obtained by Mendel:

Analyse the result and describe the mechanism of inheritance which explains these results.
OR
In humans, there is a 50% probability of the birth of a boy and 50 % probability that a girl will be born. Justify the statement on the basis of the mechanism of sex-determination in human beings.
Answer:
The ratio obtained is 9:3:3:1 in which parental as well as new combinations are observed. This indicates that progeny plants have not inherited a single whole gene set from each parent. Every germ cell takes one chromosome from the pair of maternal and paternal chromosomes. When two germ cells combine, segregation of one pair of characters is independent of other pair of characters.
OR
In human beings, the genes inherited from our parents decide whether we will be boys or girls. Women have a perfect pair of sex chromosomes (XX). But, men have a mismatched pair (XY).

All children will inherit an X chromosome from their mother regardless of whether they are boys or girls. Thus, the sex of the children will be determined by what they inherit from their father. A child who inherits an X chromosome from her father will be a girl, and one who inherits a Y chromosome from him will be a boy.

Question 28.
Plastic cups were used to serve tea in trains in early days- these could be returned to the vendors, cleaned and reused. Later,Kulhads were used instead of plastic cups. Now, paper cups are used for serving tea. What are the reasons for the shift from Plastic to Kulhads and then finally to paper cups?
Answer:

• Use of Plastic cups raised the concern towards hygiene thus they were replaced by disposable plastic cups.
• Plastic cups are non-biodegradable and harm the environment. They were thus replaced by Kulhads.
• Making Kulhad made of clay on a large scale resulted in the loss of top fertile soil.
• Now, disposable paper cups are used because – the paper can be recycled, it is biodegradable and is eco-friendly material which does not cause environmental pollution.

Question 29.
Explain where and how urine is produced?
Answer:
Blood passes through filtration units in the kidney called nephron

• Passes through glomerulus in the Bowman’s capsule – Ultra filtration
• Filtrate initially has glucose, amino acids, water, salts and nitrogenous waste
• Reabsorption – Water (as per the need of the body), Glucose and amino acids are all reabsorbed
• Secretion of excess water, salts and urea (nitrogenous waste) which makes up the urine.

Question 30.
(i) Which of the following reactions is/ are an endothermic reaction(s) where decomposition also happens?
• Respiration
• Heating of lead nitrate
• Decomposition of organic matter
• Electrolysis of acidified water
(ii) Silver chloride when kept in the open turns grey. Illustrate this with a balanced chemical equation.
Answer:
(i) Heating of lead nitrate; and electrolysis of acidified water

(ii) \(2 \mathrm{AgCl}(\mathrm{s}) \stackrel{\text { Sunlight }}{\longrightarrow} 2 \mathrm{Ag}(\mathrm{s})+\mathrm{Cl}_{2}(\mathrm{~g})\)
(No deduction for not mentioning state of reactants and products.)

Question 31.
The following table shows the position of five elements A, B, C, D and E in the modem periodic table.

Answer:
(i) D, As it is on the left side of the table in group 2.
(ii) C, as it is in the group 18/ Noble gas.
(iii) E, as we move from left to right across a period, atomic radius decreases.

Question 32.
(i) Explain the formation of calcium chloride with the help of electron dot structure. (At numbers: Ca = 20; Cl = 17)
(ii) Why do ionic compounds not conduct electricity in solid state but conduct electricity in molten and aqueous state?
Answer:

(ii) Ionic compounds do not conduct in solid state due to absence of free ions but they conduct electricity in molten and aqueous state due to presence of free ions.

Question 33.
Refractive index of water with respect to air is 1.33 and that of diamond is 2.42.
(i) In which medium does the light move faster, water or diamond?
(ii) What is the refractive index of diamond with respect to water?
Answer:
Refractive index = speed of light in vacuum / speed of light in medium.
Since the refractive index of diamond is more, hence the speed of light is lesser in diamond.
Let speed of light in water be v_w and in diamond be v_d.
Refractive index of diamond w.r.t water is say n = speed of light in water / speed of light in diamond
n = v_wv_d
Dividing both numerator and denominator by speed of light [c] we get
n = (v_w/c) (v_d/c)
= Inverse ratio of refractive index of water and diamond.
n = 2.42/1.33 = 1.82 (approx.)

Section-D

Question 34.
Match the following pH values 1,7, 10, 13 to the solutions given below:
• Milk of magnesia
• Gastric juices
• Brine
• Aqueous sodium hydroxide
Amit and Rita decided to bake a cake and added baking soda to the cake batter.

Explain with a balanced reaction, the role of the baking soda. Mention any other use of baking soda. 5
OR
(i) Four samples A, B, C and D change the colour of pH paper or solution to green, reddish- pink, blue and orange. Their pH was recorded as 7,2, 10.5 & 6 respectively. Which of the samples has the highest amount of hydrogen ion concentration? Arrange the four samples in the decreasing order of their pH.

(ii) Rahul found that the Plaster of Paris, which he stored in a container, has become very hard and lost its binding nature. What is the reason for this? Also, write a chemical equation to represent the reaction taking place.

(iii) Give any one use of Plaster of Paris other than for plastering or smoothening of walls.
Answer:

• Milk of magnesia – 10
• Gastric juices – 1
• Brine – 7
• Aqueous sodium hydroxide – 13

Baking soda undergoes thermal decomposition to form Na₂CO₃, CO₂ and H₂O; CO₂ makes the cake fluffy & soft
\(\mathrm{NaHCO}_{3} \stackrel{\text { Heat }}{\longrightarrow} \mathrm{Na}_{2} \mathrm{CO}_{3}+\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}\)

Uses:
Used in fire extinguishers/ antacid to neutralize excess acid in stomach / to neutralize the effect of acid in insect sting.
OR
(i) (a) B
(b) C,A,D,B
(ii) Due to moisture in the atmosphere it converted into gypsum
\(\mathrm{CaSO}_{4} \cdot 1 / 2 \mathrm{H}_{2} \mathrm{O}+1 / 2 \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}\)
(iii) Making toys/dolls or statues /fixing broken limbs/making decorative materials.

Question 35.
Trace the changes that take place in a flower from gamete formation to fruit formation.
Answer:
[Diagram drawn and annotated with the following points will also be considered]

• Stamen is the male reproductive part and it produces pollen grains.
• The ovary contains ovules and each ovule has an egg cell.
• The pollen needs to be transferred from the stamen to the stigma.
• If this transfer of pollen occurs in the same flower, it is referred to as self-pollination.

On the other hand, if the pollen is transferred from one flower to another, it is known as cross-pollination.
After the pollen lands on a suitable stigma, it has to reach the female germ-cells which are in the ovary. For this, a tube grows out of the pollen grain and travels through the style to reach the ovary/Figure

• The male germ-cell produced by pollen grain fuses with the female gamete present in the ovule.
• This fusion of the germ-cells or fertilisation gives the zygote.
• After fertilisation, the zygote divides several times to form an embryo within the ovule.
• The ovule develops a tough coat and is gradually converted into a seed. The ovary grows rapidly and ripens to form a fruit.
• Meanwhile, the petals, sepals, stamens, style and stigma may shrivel and fall off.

Question 36.
In the given circuit, A, B, C and D are four lamps connected with a battery of 60V.

Analyse the circuit to answer the following questions.
(i) What kind of combination are the lamps arranged in (series or parallel)?
(ii) Explain with reference to your above answer, what are the advantages (any two) of this combination of lamps?
(iii) Explain with proper calculations which lamp glows the brightest?
(iv) Find out the total resistance of the circuit.
OR
PQ is a current carrying conductor in the plane of the paper as shown in the figure below.
(i) Find the directions of the magnetic fields produced by it at points R and S?
(ii) Given r₁> r₂ where will the strength of the magnetic field be larger? Give reasons.
(iii) If the polarity of the battery connected to the wire is reversed, how would the direction of the magnetic field be changed?

(iv) Explain the rule that is used to find the direction of the magnetic field r₂ for a straight current carrying conductor.
Answer:
(i) The lamps are in parallel.

(ii) Advantages:
If one lamp is faulty, it will not affect the working of the other lamps.
They will also be using the full potential of the battery as they are connected in parallel.

(iii) The lamp with the highest power will glow the brightest.
P= VI
In this case, all the bulbs have the same voltage. But lamp C has the highest current. Hence, for lamp C, P = 5 x 60 Watt = 300 W. (the maximum).

(iv) The total current in the circuit = (3 + 4 + 5 + 3) A = 15A
The Voltage = 60V
V = IR and hence R = V/I
R= 60/15 Ω = 4Ω

OR

(i) The magnetic field lines produced is into the plane of the paper at R and out of it at S.

(ii) Field at S > Field at P Magnetic field strength for a straight current carrying conductor is inversely proportional to the distance from the wire.

(iii) The current will be going from top to bottom in the wire shown and the magnetic field lines are now in the clockwise direction on the plane which is perpendicular to the wire carrying current.

(iv) Right hand thumb rule. The thumb is aligned to the direction of the current and the direction in which the fingers are wrapped around the wire will give the direction of the magnetic field.

Students can access the CBSE Sample Papers for Class 10 Science with Solutions and marking scheme Set 1 will help students in understanding the difficulty level of the exam.

CBSE Sample Papers for Class 10 Science Set 1 with Solutions

Time: 3 Hours
Maximum Marks: 80

General Instructions:

(i) The question paper comprises four sections A, B, C and D. There are 36 questions in the question paper. All questions are compulsory.
(ii) Section-A – question no. 1 to 20 – all questions and parts there of are of one mark each.
These questions contain multiple choice questions (MCQs), very short answer questions and assertion – reason type questions. Answers to these should be given in one word or one sentence.
(iii) Section-B – question no. 21 to 26 are short answer type questions, carrying 2 marks each. Answers to these questions should in the range of 30 to 50 words.
(iv) Section-C – question no. 27 to 33 are short answer type questions, carrying 3 marks each.
Answers to these questions should in the range of 50 to 80 words. :
(v) Section—D – question no. – 34 to 36 are long answer type questions carrying 5 marks each. Answer to these questions should be in the range of 80 to 120 words.
(vi) There is no overall choice. However, internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions.
(vii) Wherever necessary, neat and properly labelled diagrams should be drawn.

Section – A

Question 1.
A women gave birth to a girl. Name the chromosome from sperm responsible for the offspring.
Answer:
Sperm with X chromosome from male is responsible for the birth of female and Y chromosome would be responsible for the male offspring. So for the given case, X chromosome from sperm is responsible for the offspring.

Question 2.
Name the gases which have replaced CFCs.
Answer:

• HFCs (Hydrofluorocarbons)
• Perfluorocarbons (PFCs) have replaced CFCs.

Question 3.
When calcium oxide is added to water, it completely dissolves in water without forming bubbles. What product is formed in this reaction?
Answer:
Ca(OH)₂

Question 4.
A plant gets rid of excess water through transpiration. What is the method used by plants to get rid of solid waste products?
Answer:
Shedding of yellow leaves

Question 5.
In peas, a pure tall plant (TT) is crossed with a short plant (tt). What is the ratio of pure tall plants to short plants in F2?
Answer:
3 : 1

Question 6.
State the direction of magnetic field in the following case.
Answer:

Perpendicular to the plane of paper in the outward direction by using Fleming’s left hand rule.

Question 7.
Why covalent compounds have low melting and boiling points?
OR
What is catenation?
Answer:
As the bond is formed by sharing of electrons between two atoms. Intermolecular forces are small between the covalent compounds. These bonds break easily.
OR
Carbon has the unique ability to form bonds with the other atoms of carbon which gives rise to large molecules. This property of self linking is called catenation.

Question 8.
What is the formula of oxide and hydride of Group I elements?
OR
What are isotopes?
Answer:
Oxide formula → R₂O; Hydride formula → RH.
‘R’ represents Group I element. F-31
OR
Isotopes are the atoms of same element having same atomic number but different mass number.

Question 9.
Why are the rings of cartilage present in air tube—Trachea?
OR
In what form is food energy stored in plants and animals?
Answer:
Rings of cartilage prevents the trachea from collapsing.
OR
Plants—Starch; Animals—Glycogen.

Question 10.
List two functions performed by the testis in human beings.
OR
What happens when a mature spirogyra filament attains considerable length?
Answer:

• To produce sperms
• To produce male sex hormone/testosterone

OR
Its filament breaks up into smaller fragments or pieces, and each fragment grows into a new filament/individual.

Question 11.
Name two human traits that show variations.
OR
How does the creation of variations in a species promote survival?
Answer:
Colours of eyes and shape of external ears.
OR
Variations increases the adaptability of an organism to its changing environmental conditions.

Question 12.
What is silvering of mirror?
Answer:
Silvering of mirror means coating the surface of mirror with a thin layer of silver, aluminium or some other shiny, opaque material.

Question 13.
Write the two raw materials for making food, used by living organisms of first tropic level.
Answer:
CO₂ and Water

Assertion (A) and Reason (R)
For question numbers 14,15 and 16, two statements are given- one labeled Assertion (A) and the other labeled 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.

Question 14.
A. Magnetic field lines have both direction and magnitude.
R. The field lines, emerge from the north pole and merge at south pole
OR
A. Compass is a small magnet and gives direction of magnetic field lines.
R. It gets deflected when brought near a bar magnet.
Answer:
(ii) OR (i)

Question 15.
A. Copper does not displace hydrogen from dilute acids.
R. Copper is less reactive than hydrogen.
Answer:
(i)

Question 16.
A. When two resistances of 4 Ω are connected in parallel total resistance is 2 Ω.
R. When two resistances of 4 Ω are connected in series total resistance is 8 Ω.
Answer:
(ii)

Answer Q. No 17 – 20 contain five sub-parts each. You are expected to answer any four sub­parts in these questions.

Question 17.
Read the following and answer any four questions from 17 (i) to 17 (v) (4 × 1 = 4)
The table below shows the results of different experiment conducted on two acids X and Y of equal concentration:

(i) Which of the following statement is correct?
(a) X is stronger acid because it has higher conductivity.
(b) Y is stronger acid because hydrogen is produced slowly when reacts with Mg.
(c) X is weaker acid because temperature change is higher when reacts with NaOH.
(d) Y is weaker acid because is has higher conductivity.
Answer:
(a) X is stronger acid because it has higher conductivity.

(ii) Select the correct relation from the following:
(a) (H+) x < (H+)y
(b) (pH) x < (pH)Y
(c) (H+) x = (H+)Y
(d) (PH) y > 7
Answer:
(b) (pH) x < (pH)Y

(iii) What will be colour of universal indicator in ‘X’?
(a) Blue
(b) Orange
(c) Green
(d) Red
Answer:
(d) Red

(iv) How many moles of H2 gas will be liberated by ‘X’ and ‘Y’ during reaction with 1 mole of Mg?
(a) 1/2
(b) 1/4
(c) 2
(d) 1
Answer:
(d) 1

(v) The gas formed when X and Y reacts with a metal carbonate is:
(a) Hydrogen
(b) Hydrogen Sulphide
(c) Oxygen
(d) Carbon dioxide
Answer:
(d) Carbon dioxide

Question 18.
Read the following and answer any four questions from 18 (i) to 18 (v) (4 × 1 = 4)
Answer:
Ohm’s law gives the relationship between current flowing through a conductor with potential difference across it provided the physical conditions and temperature remains constant. The electric current flowing in a circuit can be measured by an ammeter.

Potential difference is measured by voltmeter connected in parallel to the battery or cell. Resistances can reduce current in the circuit. A variable resistor or rheostat is used to vary the current in the circuit.

(i) Graphs between electric current and potential difference across two conductors A and B are shown in the figure. Which of the following conductor has more resistance?

(a) B
(b) A
(c) Both have equal resistance
(d) None of these
Answer:
(b) A

(ii) Seven identical lamps of resistance 220 Ω each are connected to a 220 V line as shown in figure. Then reading of the ammeter will be:

(a) \(\frac{1}{10} \mathrm{~A}\)
(b) \(\frac{2}{5} \mathrm{~A}\)
(c) \(\frac{3}{10} \mathrm{~A}\)
(d) None of there
Answer:
(d) None of there

(iii) For metallic conductor voltage uses current graph is shown at two different temperatures T₁ and T₂. From the graph it follows:

(a) T₁ = T₂
(b) T₁ > T₂
(c) T₁ < T₂
(d) None of above
Answer:
(c) T₁ < T₂

(iv) If the resistance of wire A is four times resistance of wire B then the ratio of cross sectional areas of wires is
(a) 1:2
(b) 1:4
(c) 1:8
(d) 1:6
Answer:
(b) 1:4

(v) Ohm’s law is valid only when
(a) Temperature increases
(b) Temperature decreases
(c) Graph between V and I is a straight line
(d) Pressure remains constant.
Answer:
(c) Graph between V and I is a straight line

Question 19.
Read the following and answer any four questions from 19 (i) to 19 (v) (4 × 1 = 4)
Answer:
A student took HC1 in a conical flask and was placed on a white tile with cross mark. When seen through the flask the mark was visible. On adding some sodium thiosulphate in the flask the cross marked disappeared when seen through the flask. The student observed some reaction as

(i) Name the type of reaction seen in the setup.
(a) Redox reaction
(b) Precipitation reaction
(c) Displacement reaction
(d) Double displacement reaction
Answer:
(b) Precipitation reaction

(ii) Why did the cross mark disappear?
(a) The insoluble precipitate that is formed in the flask does not allow the light to pass through it to see the cross mark.
(b) The resultant solution is dark coloured which does not allow the light to pass through it.
(c) The resultant solution has high viscosity due to which it refracts the light to other angle.
(d) The solution so formed has ability to absorb black colour hence black coloured cross is not seen.
Answer:
(a) The insoluble precipitate that is formed in the flask does not allow the light to pass through it to see the cross mark.

(iii) Give the chemical formula of the gas formed in the reaction.
(a) SO₂
(b) SO₃
(c) O₂
(d) Cl₂
Answer:
(a) SO₂

(iv) Name the resultant insoluble substance formed in the flask.
(a) Sodium sulphide
(b) Sodium sulphate
(c) Sodium sulphite
(d) Sulphur
Answer:
(d) Sulphur

(v) Which of the following reaction is of similar type as observed in the given set up.

Answer:
(a)

Question 20.
Read the following and answer any four questions from 20 (i) to 20 (v) (4 × 1 = 4)
Answer:
Analyse the following observation table showing variation of image distance (v) with object distance (u) in case of a convex lens and answer the questions that follow, without doing any calculations:

(i) What is the focal length of the convex lens? Give reason in support of your answer.
(a) -10
(b) +10
(c) -15
(d) +15

(ii) Write the serial number of that observation which is not correct.
(a) S.No. 1
(b) S.No. 4
(c) S.No. 3
(d) S.No. 6

(iii) The approximate value of magnification in case of S.No. 4 is
(a) -2
(b) -3
(c) +3
(d) +2

(iv) The image formed in case of S.No. 2 is
(a) virtual and enlarged
(b) virtual and diminished
(c) real and diminished
(d) real and enlarged

(v) If a convex lens is used to focus sunlight on a paper, where the paper should be placed so that it catches fire.
(a) At centre of curvature
(b) At principal focus.
(c) At optical centre of lens
(d) At 25 cm away from lens
Answer:
(i) (d) From S.No.3 we can say that the radius of curvature of the lens is 30 cm because when an object is placed at the centre of curvature of a convex lens its image is formed on the other side of the lens at the same distance from the lens. And, we also know that focal length is half of the radius of curvature. Thus, focal length of the lens is + 15 cm.

(ii) (d) S.No.6 is not correct as the object distance is between focus and pole, so for such cases the image formed is always virtual but in this case it is written that a real image is formed as the image distance is positive.

(iii) \(\text { (b) } m=\frac{v}{u}=\frac{+60}{-20}=-3\)

(iv) (c)

(v) (b)

Section-B

Question 21.
A 5 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 18 cm at a distance of 12 cm from it. Use lens formula to determine the position, size and nature of image formed.

The image formed is on the same side as the object, at a distance of 36 cm from the optical centre. The -ve sign shows that the image is virtual.
\(m=\frac{h_{i}}{h_{o}}=\frac{v}{u}=\frac{-36}{-12}=3\)
h₀ – 5 cm, then h_i = 3 x 5 = 15 cm The image is three times larger than the size of the object.

Question 22.
How is bleaching powder prepared? Give its chemical equation and write its two uses.
OR
A white coloured powder is used by doctors for supporting fractured bones.
(i) Write chemical name and formula of the powder
(ii) When this white powder is mixed with water a hard solid mass is obtained. Write balanced chemical equation for the change.
Answer:
Preparation: On passing chlorine gas through a test tube containing dry slaked lime Ca(OH)₂, bleaching powder is prepared.
Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O
Uses:
(i) It is used as. bleaching agent in textile industry and paper factories.
(ii) It is used as an oxidising agent in many industries.
OR
(i) Calcium sulphate hemihydrate, \(\mathrm{CaSO}_{4} \cdot \frac{1}{2} \mathrm{H}_{2} \mathrm{O}\)
(ii) \(\mathrm{CaSO}_{4} \cdot \frac{1}{2} \mathrm{H}_{2} \mathrm{O}+\frac{3}{2} \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}\)

Question 23.
(i) Choose the amphoteric oxides from the following oxides.
Na₂O, ZnO, Al₂O₃, CO₂, H₂O.

(ii) Why is it that non-metals do not displace hydrogen from dilute acids?
Answer:
(i) Al₂O₃, H₂O and ZnO are amphoteric oxides.
(ii) Non-metals cannot loose electrons so that H⁺ ions from acids become hydrogen gas and thus, cannot be displaced.

Question 24.
Find the current drawn from the battery by the network of four resistors shown in the figure.
Answer:

Equivalent resistance of the given network is

Question 25.
An element ‘E’ has following electronic configuration:

(i) To which group of the periodic table does element ‘E’ belong?
(ii) To which period of the periodic table does element ‘E’ belong?
(iii) State the number of valence electrons present in element ‘E’
(iv) State the valency of the element ‘E’
Answer:
(i) ‘E’ belongs to group 16
(ii) It belongs to 3rd period
(iii) It has 6 valence electrons
(iv) Its valency is equal to 2

Question 26.
Why is respiration considered as exothermic reaction? Explain.
OR
(i) Hydrogen being a highly inflammable gas and oxygen being a supporter of combustion, yet water which is a compound made up of hydrogen and oxygen is used to extinguish fire. Why?

(ii) What change in colour is observed when silver chloride is left exposed to sunlight? What type of chemical reaction is this?
Answer:
In respiration, glucose gets oxidized to form carbon dioxide, water and heat is evolved.
As heat energy is released during respiration it is regarded as an exothermic reaction.
OR
(i) It is because properties of compound (H₂O) are different from properties of its constituting elements, i.e., H₂ and O₂.
(ii) Silver turns black, the reaction is decomposition.

Section – C

Question 27.
Leaves of healthy potted plants were coated with vaseline to block the stomata. Will this plant remain healthy for long? State 3 reasons for your answer.
Answer:
No, this plant will not stay healthy for long. The plant will start dying because:

• Stomata gets blocked and no exchange of gases takes place.
• No intake of CO₂ for photosynthesis and O₂ for respiration.
• No transpiration and hence water transportation will be affected.

Question 28.
Describe briefly the three ways in which individual with a particular trait may increase in population.
Answer:

• Variation helps in survival of individuals.
• Sexual reproduction results in variation.
• Adaptation and natural selection.

Question 29.
How do Mendel’s experiments show that traits may be dominant or recessive?
Answer:
Mendel conducted a monohybrid cross with pea plants, and he observed that one of the contrasting characters disappears in F₁ generation. This character reappears in F₂ generation (obtained by selfing F₁) in just 25% of the progeny.

Mendel conclude that the character which expresses itself in F₁ is the dominant character while the other one which is not able to express in F₁ individuals is recessive character. This recessive character is able to express only in its pure form i.e. in 25% of F₂ individuals.

Question 30.
Study the given flow chart and answer the below given questions.

(i)
(a) Which form of the Sun’s energy is trapped by the producer?
(b) Into which energy form is the Sun’s energy converted when it is trapped by the producer?

(ii)
(a) Calculate X in the flow chart.
(b) Calculate Y on the flow chart.
(c) Label the above box on flow chart.
Answer:
(i)
(a) Light (or solar) energy
(b) Chemical energy

(ii)
(a) 1200 units
(b) 48 units
(c) Decomposers like bacteria or fungi.

Question 31.
Samples of four metals A,B, C and D were taken and added to the following solutions one by one. The results obtained have been tabulated as follows.

Use the table above to answer the following questions about metals A, B, C and D.
(i) Which is the most reactive metal?
(ii) What would you observe if B is added to a solution of copper (II) sulphate?
(iii) Arrange the metals A, B, C and D in the order of decreasing reactivity.
Answer:
(i) B is most reactive.
(ii) Blue colour of copper sulphate solution disappears and reddish brown copper metal is deposited on the metal B.
(iii) B > A > C > D is the order of reactivity.

Question 32.
Foetus derives its nutrition from the mother.
(i) Identify the tissue used for above purpose. Explain its structure.
(ii) Explain how wastes generated by developing embryo are removed.
(iii) How does the birth of child take place?
Answer:
(i) Placenta is a special tissue connection between embryo and uterine wall. It acts as an endocrine gland. It possesses villi that increases the surface area for absorption of nutrients. Facilitates passage of nutrition and oxygen to embryo from mother through blood.

(ii) Waste substances produced by embryo are removed through placenta into mother’s blood.

(iii) Birth of child takes place after the gestation period (9 months inside the womb of mother). When the pain in the uterine walls is at highest then the birth of child takes place by the birth canal.

Question 33.
(i) Show the formation of Na₂O by transfer of electrons between the combining atoms.
(ii) Why are ionic compounds usually hard?
(iii) How is it that ionic compounds in the solid state do not conduct electricity, but they do so when in molten state?
OR
(i) Which product is formed in the chemical reaction between a small strip of magnesium and nitric acid?
(ii) What happens when a pellet of sodium is dropped in water?
(iii) Identify the ‘X’ in the given reaction: P₄(s) + SO₂(g) → X
Answer:

(ii) Ionic compounds are hard due to strong force of attraction between oppositely charged i0ns.

(iii) In solid-state, ions are not free to move, whereas in molten state ions are free to move. Therefore, they conduct electricity in a molten state.
OR
(i) Mg(NO₃)₂ and 2H₂
(ii) It catches fire and forms sodium hydroxide
(iii) P₄O₁₀(s)

Section-D

Question 34.
(i) Write the functions of the following parts in human female reproductive system:
(a) Ovary
(b) Oviduct
(c) Uterus

(ii) Describe the structure and function of placenta.
OR
What is binary fission in organisms? With the help of suitable diagrams, describe the mode of reproduction in amoeba.
Answer:
(i) (a) Ovary –
• Production of female hormone
• Production of female gamete

(b) Oviduct –
• Transfer of female gamete from the ovary
• Site of fertilization

(c) Uterus –
• Implantation of the zygote
• Nourishment of the developing embryo/placenta formation.

(ii) Structure of Placenta: It is a disc-like structure embedded in the uterine wall, connected to the embryo. It has villi on the embryo’s side of the tissue and on the mother side it has blood spaces, which surround the villi.

(iii) (a) Circuit diagram

Conclusion: ‘R’ is constant at given temperature. VI graph shows straight line.

Question 36.
(i) A thin converging lens forms a
(a) Real magnified image.
(b) Virtual magnified image of an object place in front of it.
Write the positions of the object in each case.
(ii) Draw a labelled ray diagram to show the image formation in each case.
(iii) How will the following be affected on cutting this lens into two halves along the principal axis?
(a) Focal length
(b) Intensity of image formed by half lens.
OR
Analyse the following observation table showing variation of image distance (v) with object distance (u) in case of a convex lens and answer the questions that follow, without doing any calculations:

(i) What is the focal length of the convex lens? Give reason in support of your answer.
(ii) Write the serial number of that observation which is not correct. How did you arrive at this conclusion?
(iii) Take an appropriate scale to draw a ray diagram for the observation at S. No. 4 and find the approximate value of magnification.
Answer:
(i) (a) When the object is placed between ‘F’ and ‘2F’
(b) When the object is placed between pole ‘P’ and ‘F’

(ii)

(iii) No, focal length will remain the same because radius of curvature remains the same. Therefore, intensity of the image will decrease.
OR

(i)  From S.No.3 we can say that the radius of curvature of the lens is 30 cm because when an object is placed at the centre of curvature of a convex lens its image is formed on the other side of the lens at the same distance from the lens. And, we also know that focal length is half of the radius of curvature. Thus, focal length of the lens is + 15 cm.

(ii) S.No.6 is not correct as the object distance is between focus and pole, so for such cases the image formed is always virtual but in this case it is written that a real image is formed as the image distance is positive which is not possible.

(ii) Approximate value of magnification for object distance – 20 cm and image distance + 60 cm is 3.

Solved CBSE Sample Paper Class 10 Science 2020-2021 with Solutions: Solving Pre Board CBSE Sample Papers for Class 10 Science with Solutions Answers 2020-2021 Pdf Download will give students an idea about the question paper pattern, frequently asked questions, and on which topics to emphasize more in a subject. CBSE Sample Paper Class 10 Science with Solutions will boost their confidence level, and they will feel optimistic about the board exams.

CBSE Sample Paper Class 10 Science 2020-2021 with Solutions

According to the new CBSE Exam Pattern, MCQ Questions for Class 10 Science Carries 20 Marks. Click on the link below to access the CBSE Class 10 Science Sample Papers 2020 Solved.

CBSE Class 10 Science Sample Papers 2021 with Solutions

• Sample Paper Class 10 Science Set 1 (New 2020-21)
• Science Sample Paper Class 10 Set 2 (New 2020-21)
• Class 10 Science Sample Paper Set 3 (New 2020-21)
• Sample Paper of Science Class 10 Set 4 for Practice (New 2020-21)
• Sample Paper of Class 10 Science Set 5 for Practice (New 2020-21)

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