Class X - Science Practice Paper - 5 - Answers

Subject: Science

Class X

Time Allowed: 3 hours

Max. Marks: 80

General Instructions :-

This question paper has 38 questions in all . All questions are compulsory.
1. The question paper has Five sections :- Sections A, B, C, D and E .
Section A has twenty four questions(Q.No 1 to Q.No 18) that are MCQ , Assertion and Reasoning ,case study based type carry 1 marks each.
Section B has ten questions(Q.No 19 to Q.No 28) that are short answer type I carry 2 marks each.
Section C has Seven questions(Q.No 29 to Q.No 35 ) that are short answer type II carry 3 marks each.
Section D has three questions(Q.No 36 to Q.No 38) that are long answer type carry 5 marks each.
1. There is no over all choice. However, Internal choices have been provided in each section.

SECTION A

1. What is the nature of the new product which is formed by the action of water on quick lime?

(a) Neutral (b) Acidic (c) Basic (d) Amphoteric

View Answer

Ans. (c)

2. The power of a lens is -4.0 D. what is the nature and focal length of the lens?

View Answer

Ans. – 0.25 m

3. A spherical mirror and thin spherical lens have each of focal length of -15 cm. the mirror and lens are likely to be

(a) Both concave (b) Both convex

View Answer

Ans. (a)

A student plots V-I graphs for three samples of nichrome wire with resistances R₁, R₂ and R₃.

Choose from the following the statements that holds true for this graph.

             (a) R₁ = R₂ = R₃
             (b) R₁ > R₂ > R₃
             (c) R₃ > R₂ > R₁
            (d) R₂ > R₁ > R₃

View Answer

Ans. (d)

The inverse of the slope of I-V graph gives the resistance of the material. Here the slope of – Rj is highest. Thus, R₂ > R₁ > R₃

4. Identify the compound and colour formed when silver is exposed to atmosphere.

View Answer

Ans. Ag₂S, black colour

5. Which one of the given processes involves chemical reactions?

(a) Storing of oxygen gas under pressure in a gas cylinder
(b) Keeping petrol in a China dish in the open
(c) Liquefaction of air
(d) Heating copper wire in the presence of air at high temperature

View Answer

Ans. (d)

On immersing an iron nail in CuSO₄ solution for a few minutes, you will observe
(a) No reaction takes place
(b) The color of solution fades away
(c) The surface of iron nails acquire a black coating
(d) The color of solution changes to green

View Answer

Ans. (d)

6. Write the chemical formula and chemical name of Bleaching powder.

View Answer

Ans. CaOCl₂, Calcium oxychloride

7. Write the full form of ATP and NADP.

View Answer

Ans. Adenosine triphosphate (ATP)Nicotinamide adenine dinucleotide phosphate (NADP)

8. How many ATP are synthesized by complete oxidation of one glucose molecule?

View Answer

Ans. 38 molecules of ATP.

9. – Which of the following are exothermic processes?                                                                                 (a) Reaction of water with quick lime
(b) Dilution of an acid
(c) Evaporation of water
(d) Sublimation of camphor (crystals)
A)      (a) & (b)
B)      (b) & (c)
C)     (a) & (d)
D)     (c) & (d)

Ans. (a)

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10. Which nervous system is involved in increasing heart rate and breathing?

View Answer

Ans. Autonomous nervous system – sympathetic nervous system

Assertion & Reason

Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as

Both the Assertion and Reason are correct and the Reason is the correct explanation of the Assertion.
The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
Assertion is true but the Reason is false.
Assertion is false but the Reason is true.

11. Assertion: After white washing the walls, a shiny white finish on walls is obtained after two or three days. Reason: Calcium oxide reacts with carbon dioxide to form calcium hydrogen carbonate which gives shiny white finish.

View Answer

Ans. (1)

Ans. Both the Assertion and Reason are correct and the Reason is the correct explanation of the Assertion.

12. Assertion: Light travels faster in water than air. Reason: Water is denser than air.

Ans. (4)

Ans. Assertion is false but the Reason is true.

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Assertion: The phenomenon of scattering of light by the colloidal particles gives rise to Tyndall effect.

Reason: The colour of the scattered light depends on the size of the scattering particles.

View Answer

Ans. (2)

Ans. The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

13. Assertion: If a graph is plotted between the potential difference and the current flowing, the graph is a straight line passing through the origin.
Reason : The current is directly proportional to the potential difference.

Ans. (4)

Ans. Assertion is false but the Reason is true

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14. Assertion: Animals can react to stimuli in different ways. Reason: All animals have a nervous system and an endocrine system involving hormones.

Ans. (1)

Ans. Both the Assertion and Reason are correct and the Reason is the correct explanation of the Assertion.

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15. Assertion: The purpose of making urine is to filter out undigested food from intestine. Reason: Kidneys filter the waste and produce urine.

View Answer

Ans. (4)

Ans. Assertion is false but the Reason is true

16. Assertion: Baking soda creates acidity in the stomach.

Reason: Baking soda is alkaline.

View Answer

Ans. (4)

Ans. Assertion is false but the Reason is true

Assertion: Fresh milk in which baking soda is added, takes longer time to set as curd.

Reason: Baking soda decreases the pH value of fresh milk to below 6.

View Answer

Ans. (3)

Ans. Assertion is true but the Reason is false.

Case Based Question-

Read the following passage and answer any four questions

17. Whenever lime is mixed with water we get a clear solution and on touching the test tube it feels hot. That is when lime mixed with water undergoes certain changes that make it evolve heat and give a clear solution. Similarly, the iron articles undergo a change and develop a layer of rust on their surface. It reacts with the oxygen present in air and moisture and develops rust. These are chemical reaction.

17 (i) In the given equation, what does ‘X‘ stand for ?

3Fe + XH₂O— > Fe₃O₄ + 4H₂

a) 2 b) 3 c) 4 d) 5

View Answer

Ans. (c)

17 (ii) Which of the following conditions necessary for a chemical reaction?

It must be accompanied with change in temperature and pressure.
At least one of the reactants must be in fixed quantity.
It must follow the Law of conservation of mass.
All the above.

View Answer

Ans. (3)

17 (iii) What will be the colour of when copper exposed to atmosphere?

a) Silver grey c) White

b) black d) Green

View Answer

Ans. (d)

17(iv) Which one of the following involve a chemical reaction?

Storing of oxygen gas under pressure in a gas cylinder.
Liquification of air.
Keeping petrol in a china dish in the open.
Heating copper wire in the presence of air at high temperature.

View Answer

Ans. (4)

17(v) The pair(s) which will show displacement reaction is/are

NaCl solution and copper metal

AgNO₃ solution and copper metal

Al₂(SO)₄solution and magnesium metal

ZnSO₄ solution and iron metal

a) Only b c. b and c

b) c and d d. a and b

View Answer

Ans. (c)

18. Case Based Question-

Prism is a transparent optical object with flat, polished surfaces that refract light. At least two of the flat surfaces must have an angle between them.

18 (i) When light rays falls on one side of prism, it gets bent

(a) Towards the normal

(b) Away from normal

View Answer

Ans. (a)

18 (ii) In refraction of light through a prism, the light ray:

(a)Suffers refraction only at one face of the prism.

(b) Emerges out from the prism in a direction parallel to the incident ray.

(d) Bends at both the surfaces of prism opposite to its base.

View Answer

Ans. (c)

18(iii) Write The angle of Deviation from the figure.

View Answer

Ans. Angle D

18(iv) Which one is correct in the following: –

(a) i + r = A + D (b)i + e= A + D

View Answer

Ans. (d)

SECTION B

19. In one of the industrial processes, used for manufacture of sodium hydroxide, a gas ‘X’ is formed as by product. The gas ‘X’ reacts with dry slaked lime to give a compound ‘Y’ which is used as bleaching agent in textile industry. Identify X and Y. Write the chemical reaction involved in it.

View Answer

Ans. X= Chlorine Y = Calcium oxychloride

Ca(OH)₂ + Cl₂ -> CaOCl₂ + H₂O

20. One half of a convex lens is covered with a black paper:

(a) Show the formation of image of an object placed at 2F₁, of such covered lens with the help of ray diagram. Mention the position and nature of image.

View Answer

Ans.

Complete image will be formed when the one half of a convex lens is covered with a black paper. Basically the other half refract to form the final image.

Full images are formed in both the cases. It is just the intensity of the image which is different. The intensity of image in Case 1 will be half of Case 2

(b) Draw the ray diagram for same object at same position in front of the same lens, but now uncovered. Will there be any difference in the image obtained in the two cases? Give reason for your answer.

View Answer

Ans.

21. A current of 10 A flows through a conductor for two minutes.

(i) Calculate the amount of charge passed through any area of cross section of the conductor.

View Answer

Ans. Given that: I = 10 A, t = 2 min = 2 × 60 s = 120 s
(i) Amount of charge Q passed through any area of cross-section is given by I = Qt
or Q = I × t ∴ Q = (10 × 120) A s = 1200 C

(ii) If the charge of an electron is 1.6 × 10^-19 C, then calculate the total number of electrons flowing.

View Answer

Ans. (ii) Since, Q = ne
where n is the total number of electrons flowing and e is the charge on one electron
∴ 1200 = n × 1.6 × 10^-19
or n = 1200/1.6×10−19 = 7.5 × 10²¹

22. List any two observations when ferrous sulphate is heated in a dry test tube.

View Answer

Ans.

– SO₂ and SO3 gases released

– Water molecules released

– Green colour changes to reddish brown

List any two observations when water is added to quicklime.

View Answer

Ans. Hissing sound produced

Energy released

23. Define phototropism and which are the hormones responsible for phototropism?

View Answer

Ans. Movement of a part of the plant in response to light.

Positively phototropic and negatively phototropic.

Hormone- auxin

24. State reasons for the following –

1. Herbivores need a longer small intestine while carnivores have shorter small intestine

View Answer

Ans. Because of cellulose which is hard to digest

2. The lungs are designed in human being to maximize the area for exchange of gases.

View Answer

Ans. Alveoli are extremely thin walled and possess a network of capillaries for exchange of gases which becomes a fast and effective process.

25. i) In the process of respiration, state the function of alveoli.

View Answer

Ans. Increase the surface area for exchange gases. Thin wall of alveoli facilitate rapid exchange of O₂ and CO₂.

ii) Complete the following pathway showing the breakdown of glucose.

View Answer

Ans (i) Pyruvate (ii) CO₂

Rate of breathing in aquatic organism is much faster than that in terrestrial organisms.

Gastric Gland Present in the wall of Stomach

View Answer

Ans. Obtain oxygen from water present in the dissolved from through their gills.
The amount of dissolved O₂ is quite smaller as compared to the amount of O₂ in air.

26. Complete the following chart as per the given instructions – (any four)

View Answer

Ans.

HCL
Pepsin
Mucus
HCL makes medium acidic for the activation of enzyme pepsin
Pepsin breakdown proteins into peptones
Protects the inner lining of stomach from harmful action of HCL

27. Which parts of human brain is –

The main thinking part of brain

a) Responsible for maintaining the posture and balance of the body.

View Answer

Ans. (i) Forebrain (ii) cerebellum

SECTION C

28. What do the following transport?

View Answer

Xylem – water and minerals from roots t aerial part of plant
Phloem – food prepared by leaves, amino acids, hormones
Pulmonary vein – oxygenated blood from lungs to left atrium
Vena Cava – deoxygenated blood to right atrium
Pulmonary artery – deoxygenated blood from right atrium to lungs
Aorta – oxygenated blood from left atrium to arteries

29. Describe the structure and function of nephron with the help of labeled diagram.

View Answer

Ans. Nephron- filtration of blood and elimination of waste material.

Water, amino acids, minerals, ions are reabsorbed

Write the main function of following –

View Answer

Sensory neuron – receive stimuli through their dendrites and transmits the CNS
Vertebral column – protection of spinal cord
Motor neuron- transmits impulses from CNS towards muscles or glands

30. Explain the following by giving chemical equation in each case:

a. Baking soda is heated.

View Answer

Ans. NaHCO₃ — > Na₂CO₃ + H₂O + CO₂

b. Gypsum is heated at 373 k

View Answer

Ans. CaSO₄.2H₂O — > CaSO₄.1/2H₂O + 11/2H₂O

c. Hydrochloric acid react with caustic soda

View Answer

Ans. HCl + NaOH — > NaCl + H₂O

(i) What is baking powder? How does it make the cake soft and spongy?

View Answer

Ans. When tartaric acid is mixed with baking soda it is called baking powder. When it get heated it released CO₂ gas that make it soft and spongy.

(ii) How is tooth decay related to pH?

View Answer

Ans. As pH value of our mouth decreases below 5.5 acid character increases that decay the tooth.

31. What are plant hormones? Name the plant hormones responsible for the following –

View Answer

Ans. Naturally produced chemicals capable of translocation and regulating physiological process.

Growth of stem – Gibberllins or gibberelic acid
Promotion of cell division – Cytokinins
Inhibition of growth – Abscisic acid

Name the hormone secreted by the following endocrine gland and specify one function of each.

View Answer

Thyroid- thyroxine (T4), triiodothy (T3), calcitonin

Regulate the oxidation of carbohydrates, fats and protein

Pancreas – insulin and glucagon

Pituitary – growth hormone and somatotropic hormone ; thyroid stimulating hormones; adrenocorticotropic hormone; follicle stimulating hormone; luteinizing hormone; protection hormone; melanocyte stimulating hormone; oxytocin; vasopressin

32. Mention with reason the colour changes observed when-

a. Silver chloride exposed to sunlight.

View Answer

Ans. White to grey because AgCl decomposes to produce Ag and Cl

b. Copper powder is strongly heated in the presence of oxygen.

View Answer

Ans. Brown to black because CuO is formed.

c. A piece of zinc dropped in copper sulphate solution.

View Answer

Ans. Blue to colourless because ZnSO₄ if formed.

33. An object 4 cm in height, is placed at 15 cm in front of a concave mirror of focal length 10 cm. At what distance from the mirror should a screen be placed to obtain a sharp image of the object. Calculate the height of the image.

View Answer

Ans. object distance, u = -15 cm,
object height, h = 4 cm, focal length f = -10 cm;
Image distance, v = ?
Using mirror formula,
1v+1u=1f⇒1v+1(−15)=1−10⇒1v=115−110
or 1v=10−15150=−5150=−130 or v = -30
In order to obtain a sharp image of the object on the screen, screen should be placed at a distance of 30 cm in front of the mirror.
Also, magnification, m = h′h=−vu
or h′4=−(−30)(−15) or h’ = −(30)×4(15) = -2 × 4
or h’ = -8 cm
Thus, the height of the image is 8 cm.

34. Draw a schematic diagram of a circuit consisting of a battery of 3 cells of 2 V each, a combination of three resistors of 10 Ω, 20 Ω and 30 Ω connected in parallel, a plug key and an ammeter, all connected in series. Use this circuit to find the value of the following :
        (a) Current through each resistor
        (b) Total current in the circuit
       (c) Total effective resistance of the circuit.

View Answer

Ans. The circuit diagram is as shown below.

(a) Given, voltage of the battery = 2V + 2V + 2V = 6 V
Current through 10 Ω resistance,
I₁₀ = V/R=6/10 = 0.6 A
Current through 20 Ω resistance,

I₂₀ = V/R=6/20 = 0.3 A
Current through 30 Ω resistance,
I₃₀ = V/R=6/30 = 0.2 A
(b) Total current in the circuit, 1= I₁₀ + I₂₀ + I₃₀
= 0.6 + 0.3 + 0.2 = 1.1 A
(c) Total resistance of the circuit,
1/R_P=1/10+1/20+1/30=11/60 R_P = 60/11 = 5.45Ω

35.

A boy uses spectacles of focal length – 60cm. He had few doubts in his mind and consults doctor for clearing them. Answer the below questions by using the above information.

(a) Name the defect of vision he is suffering from.

View Answer

Ans. Myopia

(b) Draw the diagram of correction of this defect of an eye.

View Answer

Ans.(i). Excessive curvature of eye lens (ii). Elongation of eyeball

SECTION D

36. a. Give the answer as given instructions:-

(i) “The magnification produced by a spherical mirror is -3”. List four information’s you obtain from this statement about the mirror/ image.

(ii). The image of an object formed by a lens is of magnification -1. If the distance between the object and its image is 60 cm, what is the focal length of the lens? If the object is moved 20 cm towards the lens, where would the image be formed? State reason and also draw a ray diagram in support of your answer.

View Answer

Ans. (i). Negative sign of magnification indicates that the image is real and inverted. Since the image is real and inverted, the mirror is concave and magnification of -3 indicates that the image is magnified.(ii). Magnification of -1 indicates that the image is real and inverted and is of the same size as of the object. The object must be at 2f and image also at 2f on the other side.
Total distance between image and object
Also 4f = 60 cm ⇒ f = 15 cm
If object is moved 20 cm towards the lens, then the object will be between focus and optical centre of the lens and image formed will be virtual and erect and on the same side of the lens.

37. a. Give reason for the following statements: –

(i). A tarnished copper vessel regains its shine when rubbed with lemon.

View Answer

Ans. Green layer of copper carbonate is formed which is basic in nature when rubbed with lemon containing acid neutralization occur.

(ii). Rain water conducts electricity but distilled water does not.

View Answer

Ans. Rain water contains ions but distilled water does not contain.

(iii). The crystals of washing soda change to white powder on exposure to air.

View Answer

Ans. Washing soda loses 9 water molecules when exposed to air and turns white.

b. Show with an activity that dry HCl is not acidic in nature.

38. Case based question–

There is a pair of bean- shaped organs B in the human body towards the backs, just above the waist. A waste product D formed by the decomposition of unused proteins in the liver is brought into organ B though blood by an artery O. The numerous tiny filters P present in organ B clean the dirty blood by removing the waste product D. The clean blood goes into circulation through the vein U. The waste substance D, other waste salt and excess water from a yellowish liquid w which goes to organ B into a bag like structure C through two tubes F. This liquid is then thrown out of the body through a tube E.

Name artery O and Vein U.

View Answer

Ans. Renal artery and pulmonary vein

View Answer

What are tiny filters P known as.

View Answer

Ans. Nephron

View Answer

What is organ B and waste substance D.?

View Answer

Ans. Kidney and vein

View Answer

Name the liquid, structure C, tubes F, and tube E.

View Answer

Ans. Urine- w ; bladder- c ; uriters- f ; urethra- e

View Answer

Class X – Science Practice Paper – 5 – Answers