Class 10 Physics

# Model Question

## Sample Paper 2

These sample papers have been taken from CBSE (www.cbse.nic.in)

• Questions 1 and 2 are one-mark questions
• Questions 3 to 5 are two-mark questions
• Questions 6 to 15 are three-mark questions
• Questions 16-21 are five-mark questions
• Questions 22 to 27 are two-marks questions, and are based on practical skills

### Section – A

Question 1: Which type of lens is used for the correction of myopia?

Question 2: What is the meaning of power of accommodation of human eye?

Answer: Human eye has the capability to clearly see a nearby object as well as a distant object. This capability of human eye is called power of accommodation.

Question 3: An aqueous solution of a substance ‘P’ is used in white washing. Name the substance ‘P’ and write its chemical formula. Also write the chemical equation for the reaction of substance ‘P’ with water.

Answer: Substance ‘P’ is washing soda (Sodium carbonate)

Chemical Formula of Washing Soda = Na2CO3

Reaction between sodium carbonate and water is given by following equation:

Na_2CO_3+H_2O→2NaOH+CO_2

Question 4: List two energy sources that you would consider to be renewable. Give reasons for your choice.

Answer: Wind is circulated by various natural processes and takes negligible time. The sun keeps on emitting solar energy continuously. Hence, both solar energy and wind energy can be considered as renewable sources of energy.

Question 5: What are trophic levels? Make a food chain of four trophic levels.

Answer: Different levels in the food chain are called trophic levels. Following is a food chain with four trophic levels:

Grass → Grasshopper → Frog → Snake

Question 6: Write the chemical formula of bleaching powder. How is it prepared? Write balanced chemical equation for the reaction involved. Write one important use of bleaching powder.

Answer: Formula of Bleaching Powder: CaOCl2

Preparation of Bleaching Powder: When calcium hydroxide (slaked lime) reacts with chlorine, it gives calcium oxychloride (bleaching powder) and water is formed.

Ca(OH)_2 + Cl_2 → CaOCl_2 + H_2O

One Important Use of Bleaching Powder: As disinfectant for cleaning water

OR

A sulphate salt of group two element of the periodic table is white, soft substance, which can be moulded into different shapes by making it dough. When this compound is left in open for sometime, it becomes a solid object and cannot be used for moulding purposes. Identify this sulphate salt and explain why does it show such a behaviour. Also give the equation for the reaction involved.

Answer: This substance is Plaster of Paris. When it reacts with water, it turns into gypsum which is a hard substance. Due to this, when plaster of Paris is left in open for some time, it absorbs moisture and turns into hard solid. The reaction is as follows:

CaSO_4.(0.5)H_2O + (1.5)H_2O→ Ca\SO_4.2H_2O

Question 7: Distinguish between ethanol and ethanoic acid on the basis of (i) litmus test and (ii) reaction with sodium hydrogen carbonate. Write the name and formula of the oxidizing agent used in the conversion of ethanol to ethanoic acid.

Answer: Ethanol changes red litmus to blue, while ethanoic acid changes blue litmus to red.

Ethanol does not react with sodium hydrogen carbonate, but ethanoic acid reacts with sodium hydrogen carbonate to give sodium acetate.

CH3COOH + NaHCO3 → CH3COONa + CO2 + H2

Potassium Permanganate (KMnO4) or Potassium Dichromate (K2Cr2O7) is used for conversion of ethanol to ethanoic acid.

Question 8: The elements Li, Na and K each having one valence electron are in the 2nd, 3rd and 4th period respectively of Modern Periodic Table.

Answer the following questions giving reasons:

(i) In which group should they be placed?

(ii) Which one of these elements is least reactive?

(iii) Which one of these elements has the largest atomic radius?

Question 9:

(a) State the role performed by plant hormones. Name a plant hormone which is essential for cell division.

Answer: Plant hormones facilitate chemical coordination in plants. Cytokinin is essential for cell division.

(b) Name and explain the role of plant hormone involved in phototropism.

OR

(a) Name the gland that secrete: (i) insulin, (ii) thyroxin

Answer: (i) Pancreas (ii) Thyroid gland

(b) Explain with an example how the timing and amount of hormone secreted are regulated in a human body.

Answer: Hormonal control is mainly based on feedback mechanism and tells the body to either pace up or slow down; as per the situation. So, timing and amount of hormone released by a particular gland depend upon the specific need of the situation. For example; adrenaline is released by adrenal gland when the body faces a stress situation. Amount of adrenaline to be released also depends on the degree of stress. Body gets ready accordingly as per the challenge it is going to face.

Question 10:

(a) Name the part of human brain which controls: (i) voluntary actions (ii) involuntary actions

Answer: (i) Cerebrum (ii) Medulla

(b) State the significance of peripheral nervous system. Name the components of this nervous system and distinguish between their origins.

Answer: Peripheral nervous system works as the conduit between the central nervous system and various organs of the body. Peripheral nervous system is composed of two types of nerves, viz. cranial nerves and spinal nerves. Cranial nerves come out of the brain, while spinal nerves come out of the nerve cord.

Question 11: What are fossils? How are these formed? List two methods of determining the age of fossils.

Answer: Preserved remains of animals and plants from distant past are called fossils. Fossils are formed when a living being gets buried under sediment and remain there for hundreds of years. Two main processes of formation of fossil are called permineralisation and mould or cast formation. Two methods of determining the age of fossil are stratigraphy and carbon dating.

OR

What is speciation? List four factors responsible for speciation.

Answer: The evolutionary process by which populations evolve to become distinct species is called speciation. Four factors responsible for speciation are as follows:

• Geographical Isolation
• Genetic Drift
• Natural Selection
• Reduction in Gene Flow

Question 12: Explain giving reason why the sky appears blue to the observers from the surface of the Earth. What will be the colour of the sky for an Astronaut staying in an International Space Station orbiting the Earth? Explain your answer with reason.

Answer: We know that the wavelength of red colour is more than that of blue colour. The size of particles in air is smaller than the wavelength of visible light. Hence, these particles scatter the light of shorter wavelength more effectively than light of longer wavelength. The blue end of the visible spectrum has shorter wavelength than the red end. Due to this, blue colour is scattered more strongly in the atmosphere; compared to the red colour. This is the reason sky appears blue. No color is scattered in space. Hence, the sky appears black to the astronaut staying in International Space Station.

Question 13: We know that an electric current through a metallic conductor produces a magnetic field around it. Explain giving reason whether a similar magnetic field will be produced around a thin beam of moving (i) alpha particles, (ii) neutrons. Name the rule applied to determine the direction of magnetic field produced around a current carrying straight conductor.

Answer: Since alpha particles are charged particles so a magnetic field will be produced around the beam of moving alpha particles. But as neutrons are electrically neutral to this will not happen in case of a beam of neutrons. Right Hand Thumb Rule explains the direction of magnetic field produced around a current-carrying straight conductor.

Question 14: Explain the role of an electric fuse joined in series with an electrical appliance. Why should a fuse with a defined rating not be replaced by one with a larger rating?

Answer: Electric fuse is a safety device which breaks the circuit in case of overload or short-circuit. Thus, the electric fuse helps in preventing any damage to the electrical appliance. If an electric fuse with larger rating is used for an appliance the fuse will not melt in case of overload. Thus, it will not do the work for which it has been installed.

Question 15: We are all familiar with the “Chipko Movement” which originated in the early 1970s in a remote village of Garhwal high up in Himalayas. This was a result of dispute between the local villagers and a greedy contractor who had been allowed to fell the trees in a forest close to the village. When contractor’s workers appeared in the forest to cut the trees, the men folk were not present, so the women folk took the lead in the movement of preventing the contractor from felling the tree.

They hugged the trees and forced the contractor to withdraw:

(i) Why were the villagers against felling of trees?

Answer: The villagers wanted to protect their environment. So, they were against the felling of trees.

(ii) How do forests maintain ecological balance in nature?

Answer: Trees help in maintaining the balance between carbon dioxide and oxygen in air. Trees help in precipitation by way of transpiration. Trees also provide habitat to a large variety of creatures. Thus, forests maintain ecological balance in nature.

(iii) List two values exhibited by the “Chipko Movement”.

Answer: Two values exhibited by this movement are:

• Concern for environment
• Concern for living beings

Question 16:

(a) What is a balanced chemical equation? Why should chemical equations be balanced?

Answer: A balanced chemical equation has number atoms of each element equal on both sides. According to Law of Conservation of Mass, mass can neither be created nor destroyed in a chemical reaction. To obey this law, the total mass of elements present in reactants must be equal to the total mass of elements present in products.

(b) Write the chemical equation of the reaction in which the following changes have taken place:

(i) Change in colour.

Answer: CuSO4 + Fe → FeSO4 + Cu

(ii) Change in temperature.

Answer: NaOH + HCl → NaCl + H2O

(iii) Formation of precipitate.

Answer: BaCl2 + Na2SO4 → BaSO4 (ppt)+ 2NaCl

Question 17:

(a) Explain why the method of extraction of metals high up in the reactivity series is different from the method of extraction of metals in the middle of the series. Why cannot the same process be applied for them?

Answer: Carbon is used for reduction of metals ores from middle of the series. But carbon is less reactive than metals of high reactivity. So, metals of high reactivity cannot be extracted by the same process as used for metals of middle reactivity.

(b) With the help of equation explain the process of extraction of sodium.

Answer: When electric current is passed through molten state or solution of sodium chloride, sodium metal deposited over cathode.

Na+ + e → Na

2Cl − e → Cl2

2NaCl → 2Na + Cl2

OR

(a) What are amphoteric oxides? Give examples of two amphoteric oxides.

Answer: Metal oxides are generally basic in nature. But oxides of some metals show dual nature, i.e. acidic and basic nature. Examples: Al2O3 and ZnO

(b) What is Cinnabar? How is metal extracted from Cinnabar? Explain in brief.

Answer: Cinnabar (HgS) is the ore of mercury. Cinnabar (HgS) is first heated in air. This turns HgS [mercury sulphide or cinnabar] into HgO (mercury oxide); by liberation of sulphur dioxide.

Mercury oxide so obtained is again heated strongly. This reduces mercury oxide to mercury metal.

2HgS + 3O2 → 2HgO + 2SO2

2HgO → 2Hg + O2

Question 18:

(a) Write the name of different components of transport system in human beings and state their functions in brief.

Answer: Different Components of Transport System in Human Beings are as follows:

OrganFunction
HeartPumping the blood
BloodCarrying food, oxygen and other materials
Blood VesselsServing as channel for blood flow

(b) How is blood clot form, if a leak develops in the system of blood vessels?

Answer: In case of leak in the system of blood vessel, platelets and fibrin create a mesh-like structure at the site of injury. The mesh-like structure forms the clot.

Question 19: What is Pollination? How does it occur in plants? Explain how pollination leads to fertilisation.

Answer: Transfer of pollen grains from anthers to stigma is called pollination. Plants carry out pollination in two ways, viz. sel-pollination and cross-pollination.

Self Pollination: When pollen grains land on the stigma of the same flower, it is called self-pollination.

Cross Pollination: When pollen grains land on the stigma of a different flower, it is called cross-pollination. Plant takes help of various agents to facilitate cross-pollination.

After pollination, pollen grains germinate and produce pollen tubes. The pollen tube pierces through the style to reach the egg apparatus. Pollen nuclei are finally transferred to the egg apparatus and fertilization takes place.

Question 20:

(a) State the laws of refraction of light.

Answer: Laws of Refraction of Light

1. The incident ray, refracted ray and normal to the interface of given two transparent media, all lie in same plane.
2. The ratio of sine of angle of incidence and sine of angle of refraction is always constant for the light of given colour and for the pair of given media.

The Second Law of Refraction is also known as Snell’s Law of Refraction.

That is, (text(Sin) i)/(text(Sin) r)= constant

(b) What is meant by absolute refractive index of a medium?

Answer: When one medium is taken as vacuum and speed of light is taken in it, then the refractive index of second medium with respect to vacuum is called Absolute Refractive Index and it is generally denoted by n2.

Thus, n_2=text(Speed of light in vacuum)/text(Speed of light in given medium)

(c) The absolute refractive index of diamond is 2.42. If the absolute refractive index of glass is 1.5 and the speed of light in glass is 2 × 108 m/s, calculate the speed of light in diamond.

n_2=text(Speed of light in vacuum)/text(Speed of light in given medium)

Or, 1.5=text(Speed of light in vacuum)/(2xx10^8)

Or, Speed of light in vacuum =1.5xx2xx10^8=3xx10^8 m/s

Now, for diamond:

2.42=text(Speed of light in vacuum)/text(Speed of light in given medium)

Or, 2.42=(3xx10^8)/text(Speed of light in diamond)

Or, Speed of light in diamond = (3xx10^8)/(2.42)=1.24xx10^8 m/s

OR

(a) State the laws of reflection of light.

Answer: Laws of reflection of light:

1. The angle of incidence and angle of reflection is equal.
2. The incident ray, reflected ray and normal to the point of reflection lie in the same plane.

(b) List any two characteristics of the images formed by plane mirrors.

Answer: Erect and virtual

(c) An object is placed in front of a spherical mirror of focal length –20 cm at a distance of 30 cm. At what distance from the mirror a screen be placed in order to obtain a sharp image of the object on it?

Answer: Given: f = -20 cm, u = -30 cm

Image distance can be calculated as follows:

1/v-1/u=1/f

Or. 1/v=1/f+1/u

Or, 1/v=-1/(20)-1/(30)

Or, 1/v=(-3-2)/(60)=-5/(60)

Or, v=-(60)/5=-12 cm

Question 21:

(a) Define electric power. Express it in terms of potential difference ‘V’ and resistance ‘R’.

Answer: Rate of transfer of electrical energy through a circuit in unit time is called electric power. The SI unit of electric power is watt (W). It can be expressed in terms of V and R as follows:

1W=1 text(volt)xx 1 text(ampere)

=1V\xx1A

(b) An electric motor takes 5.0A from an electric source of 220 V. Determine the power of the motor and calculate the energy consumed by the motor in kWh, when it runs for 5 hours.

Answer: Given: Current I = 5 A, V = 220 V, time = 5 hours = 5 × 60 × 60 s

Power =VxxR

=220xx5=1100 W

Now power consumed in 5 hours

=1100 W\xx5xx3600=19800000 W

=1.98xx10^7 kWh

### SECTION-B

Question 22: State observations of the reactions of dil. HCl with the following:

(i) Blue litmus paper

Answer: Blue litmus paper turns red

(ii) Red litmus paper

(iii) Zinc-granules

Answer: Strong effervescence is observed which happens due to formation of hydrogen gas during the reaction between zinc and hydrochloric acid.

Zn + 2HCl → ZnCl2 + H2

(iv) Solid NaHCO3

Answer: When hydrochloric acid reacts with sodium hydrogen carbonate, the reaction gives sodium chloride and carbon dioxide.

HCl + NaHCO3 → NaCl + H2 + CO2

Question 23: You have two samples of water marked A and B. How would you distinguish between the two if one sample is of soft water and the other is of hard water?

Answer: Samples of soft water and hard water can be distinguished with the help of a test of foam formation. For this, soap is used with particular sample of water. Amount of foam is checked. After that, the time for which the foam does not disappear is also checked. Soap easily forms foam in soft water compared to in hard water. So, this apparently simple test helps us in differentiating between samples of soft and hard water.

Question 24: Your friend is preparing a temporary mount of a leaf peel to observe stomata. At which stage of preparation, should he use a stain and glycerine. State the role of these two liquids.

Answer: Stain imparts color to various membranes in the cell and thus helps in marking the boundaries of cells. Glycerine prevents drying up of specimen.

Question 25: When a student observes a slide showing different stages of binary fission in Amoeba, he generally observes four stages of the process. Describe these stages in a proper sequence.

Answer: Four stages in binary fission of amoeba are as follows:

Mother cell: The mature mother cell can be seen by presence of distinct nucleus.

Division of Nucleus: Some cells show nucleus dividing into two.

Division of cytoplasm: Some cells show division of cytoplasm. It is clear by appearance of two smaller cells joined somewhere in the middle.

Daughter cells: Daughter cells are smaller than mother cell and no two daughter cells are joined to one another.

Question 26: A student has to determine the focal length of a given concave mirror by focusing a distant object. Answer the following questions:

(i) Which two precautions should he observe while selecting the object?

Answer: The object should be not too large nor too small.

(ii) Which distance should he measure to determine the focal length and why?

Answer: We know that when object is at infinity, it’s highly diminished and inverted image is formed at focus of concave mirror. Hence, the student should measure the distance between image of a distant object and the mirror to measure the focal length.

Question 27: List four precautions which a student observes while performing the experiment of determining the equivalent resistance of a combination of two resistors connected in series.

Answer: Precautions to be observed to determine equivalent resistance of two resistors in series:

• Ends of wires should be properly cleaned with sandpaper.
• Plug key should be in ON position only for a short duration.
• Battery should be fully charged before the experiment
• Connections should be tightly fit.

OR

In the experiment of studying the dependence of potential difference (V) across a resistor on the current (I) passing through it a student has tabulated a set of six observations. If, now he draws a graph between V and I, what will be the shape of the graph and what conclusion can be drawn from it?

Answer: The graph of V (potential difference) versus I (electric current) is always an upwardly slanting straight line. This shows that potential difference varies directly as electric current.

CHAPTER LIST