Class 10 Physics

# Model Question

## Sample Paper 1

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: Mendel took tall pea plants and short pea plants and produced F1 progeny through cross-fertilisation. What did Mendel observe in the F1 progeny?

Answer: Mendel observed that all the plants in the F1 generation were tall plants.

Question 2: Name two constituents of biogas.

Answer: Methane and Carbon dioxide

Question 3: Carbon has four electrons in its valence shell. Which type of compounds can be formed by carbon atom and why? Give any one example of such compounds.

Answer: Carbon needs to gain or lose 4 electrons in order to make an ionic compound. But doing so requires a huge amount of energy. Hence, carbon makes compounds by sharing its electrons and thus makes covalent compounds. CCl4 (Carbon tetrachloride) is one such example. In this compound, carbon shares its valence electrons one each with one atom of chlorine.

Question 4: Different parts of brain are associated with specific functions. Name the part of human brain which performs the following functions:

1. Sensation of feeling full: Hind brain
2. Vomiting: Pons
3. Picking up a pencil
4. Riding a bicycle

Answer: (a) Hypothalamus, (b) Medulla, (c) Cerebrum and cerebellum, (d) Cerebrum and cerebellum

Question 5: An object is kept 40 cm in front of a concave mirror of focal length 20 cm. Find the position and nature of the image. Draw a ray diagram to show the formation of image in this case.

Answer: Given, u = -40 cm, f = -20 cm, v = ?

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/(-40)

Or, 1/v=(-2-1)/(40)=-1/(40)

Or, v=-40

So, image is formed at 40 cm in front of mirror.

Negative sign shows it is an inverted image.

Image distance is same as object distance, hence image is of same size as object.

As it is formed in front of mirror so it is a real image

Question 6: In the reaction:

MnO2 + 4HCl → MnCl2 + 2H2O + Cl2

(a) Name the compound (i) oxidised, (ii) reduced.

Answer: HCl is getting oxidized and MnO2 is getting reduced

(b) Define oxidation and reduction on its basis.

Answer: Removal of hydrogen is called oxidation, while removal of oxygen is called reduction.

Question 7: 1 g of solid sodium chloride is taken in a clean and dry test tube and 2 mL of conc. sulphuric acid is added to it. If the gas evolved is tested first with dry and then with wet blue litmus paper, in which case will the litmus paper change colour? Give reason for your answer. What inference can be drawn about the nature of the evolved gas? Support your answer with chemical equation for the reaction.

Answer: Following reaction takes place when sodium chloride reacts with sulphuric acid:

2NaCl + H2SO4 → Na2SO4 + 2HCl

HCl dissociates into ions only in the presence of water. So, dry litmus paper does not show color change but wet litmus paper (blue) changes to red. This shows that HCl is acidic.

OR

(a) For the preparation of cakes, baking powder is used. If at home your mother uses baking soda instead of baking powder, how will it affect the taste of the cake and why?

Answer: When baking soda is heated, it gives sodium carbonate; as shown by following equation:

2NaHCO_3→Na_2CO_3+CO_2+H_2O

Formation of sodium carbonate, results in bitter taste in the cake, which is not desirable for a tasty cake.

(b) How is baking soda be converted into baking powder?

Answer: Baking soda is converted into baking powder by addition of a edible oil (generally tartaric acid).

(c) What makes the cake soft and spongy?

Answer: Production of carbon dioxide results in formation of a large number of bubbles in the cake mixture. This results in cake becoming soft and spongy.

Question 8: What happens when hydrogen is added to a vegetable oil in the presence of nickel? Name the reaction and write one difference between the physical property of the vegetable oil and the product obtained in this reaction. Write the role of nickel in this reaction.

Answer: When hydrogen is added to a vegetable oil in presence of nickel, the vegetable oil becomes saturated. This reaction is called hydrogenation and is generally used to produce margarine from vegetable oil. While the vegetable oil is a viscous liquid, margarine is semi-solid. Nickel is the catalyst in this reaction.

Question 9: What is geotropism? Draw a labelled diagram of a potted plant showing positive geotropism and negative geotropism.

Answer: The growth in a plant part in response to the gravity is called geotropic movement, or geotropism. Following figure shows positive and negative geotropism in a plant. Roots are positive geotropism while stem is showing negative geotropism.

Question 10: What are acquired traits? Why are these traits generally not inherited over generations? Explain.

Answer: Traits; which are acquired due to interaction with the environment; are called acquired traits. Acquired traits are not inheritable because such traits do not change the genotype of an individual.

Question 11: We wish to obtain an equal sized inverted image of a candle flame on a screen kept at distance of 4 m from the candle flame.

(a) Name the type of lens that should be used.

Answer: Convex Lens

(b) What should be the focal length of the lens and at what distance from the candle flame the lens be placed.

Answer: The focal length of the lens should be 2 m and candle flame should be at 4 m, i.e. twice the focal length. We know that when an object is placed at 2F1 of a convex lens, image is formed on 2F2. The image is of same size, real and inverted.

(c) Draw a labelled diagram to show the image formation in this case.

Answer: OR

A 5 cm tall object is placed at a distance of 30 cm from a convex mirror of focal length 15 cm. Find the position, size and nature of the image formed.

Answer: Given, f = 15 cm, u = -30 cm, h1 = 5 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/(15)+1/(-30)

Or, 1/v=(2-1)/(30)=1/(30)

Or, v=30 cm

We know that v/u=(h_2)/(h_1)

Or, (h_2)/5=(30)/(30)

Or, h_2=5 cm

Image is of same size, erect and virtual.

Question 12: Consider the following circuit: What would be the readings of the ammeter and the voltmeter when key is closed? Give reason to justify your answers.

Answer: Let us find equivalent resistance for this combination of resistors

For series combination, equivalent resistance is given as follows:

R=R_1+R_2+R_3

Or, R=5+8+12=25 Ω

Using Ohm’s law we can find the current:

V = IR

Or, I=V/R

Or, I=(6)/(25)=0.24 ampere

Now, reading on voltmeter can be calculated as follows:

V=IR

Or, V=0.24xx12=2.88 V

OR

What is electrical resistivity? Derive its SI unit. In a series electrical circuit comprising a resistor made up of a metallic wire, the ammeter reads 100 mA. If the length of the wire is doubled, how will the current in the circuit change? Justify your answer.

Answer: If l is the length and A is the area of cross section of a conductor, then resistance R is given by following:

R∝l/A

Or, R=ρl/A

Here, ρ is the constant of proportionality and is called electrical resistivity of the material of conductor.

Above equation can also be written as:

ρ=(RA)/l

Since SI unit of resistance is Ω that of area is m2 and that of length is m hence,

ρ=(Ωxx\m^2)/m=Ω m

We know that resistance varies directly as length of the conductor. So, doubling the length of the wire will result in resistance becoming double. This will reduce the current to half of earlier value, because current varies inversely as resistance.

Question 13: Calculate the total cost of running the following electrical devices in the month of September, if the rate of 1 unit of electricity is Rs. 6.00.

(i) Electric heater of 1000 W for 5 hours daily.

Answer: There are 30 days in September

So, monthly consumption =30xx5 h\xx\1000 W=150000 Wh

=150 kWh=150 unit

Total cost =6xx150=Rs. 900

(ii) Electric refrigerator of 400 W for 10 hours daily.

Answer: Monthly consumption =30xx10 h\xx\400 W=120000 Wh

=120 kWh

Total cost =6xx120=Rs. 720

Question 14: While teaching the chapter “Our Environment” the teacher stressed upon the harmful effects of burning of fossil fuels, plastic, paper etc. The students noticed the extensive use of plastic and polythene in daily life, which can be avoided and the surroundings can be kept clean. They decided to make their school “plastic and polythene” free and motivated each other for its minimum use.

(a) Why should the use of polythene and plastic be reduced in daily life?

Answer: Polythene and plastic are non-biodegradable and a significant portion of them cannot be recycled. This creates the problem of accumulation of plastic waste in our surroundings which is detrimental to the environment. So, we need to reduce the use of polythene and plastic in our daily life.

(b) In what ways the students would have avoided the use of plastic and polythene in their school?

Answer: The students could avoid the use of plastic and polythene in school in following ways:

• Using jute bags to bring any extra item to school.
• Asking the canteen staff to use paper plates instead of plastic plates.
• Asking parents to buy metallic water bottles, and lunch boxes instead of plastic ones.

(c) How the students would have motivated each other for the success of their decision?

Answer: Students can apply various ways and means to motivate each other for the success of their decision. This can be done through active dialogue, through suggestions and feedbacks. This can also be done by organizing some street plays to raise awareness level.

Question 15: What is “Sustainable Management of Natural Resources”? Why is it necessary? Which one out of reuse and recycle, would you practise in your daily life and why?

Answer: The practice of managing natural resources so that current generations needs should be met without jeopardizing the needs of the future generation is called Sustainable Management of Natural Resources. It is necessary in order to ensure that natural resources shall be available for many generations to come. I would prefer to reuse rather than recycle. Recycling required usage of some resources (fuel and some raw materials), but reuse does not involve usage of any other resource. So, ‘reuse’ is always better in terms of conservation of resources.

Question 16:

(a) List in tabular form any three chemical properties on the basis of which metals and non-metals are differentiated.

Answer:

MetalsNon-metals
Metals react with oxygen to make basic oxides.Non-metals react with oxygen to make acidic oxides.
Some metals displace hydrogen from dilute acidNon-metals do not react with dilute acids.
Metals make ionic compoundsNon-metals form covalent compounds.

(b) State two ways to prevent the rusting of iron.

Answer: Painting and galvanization

Question 17: Explain giving justification for the trends in the following properties of elements, on moving from left to right in a period, in the Modern periodic Table.

(a) Variation of valency.

Answer: Valency first increases up to 4 on moving from left to right in a period and then decreases up to zero. This happens because number of valence electrons increases from 1 to 8. Valency is 1 for elements with valence electrons 1 or 7, is 2 for those with valence electrons 2 or 6, and so on.

(b) Change of atomic radius.

Answer: Atomic size and atomic radii decrease from left to right in a period. This happens because of decrease in electropositivity.

(c) Metallic to non-metallic character.

Answer: Metallic character decreases from left to right in a period. This happens because of decrease in electropositivity.

(d) Electronegative character.

Answer: With reduction in atomic size, a tendency to gain electrons increases across a period. Hence, electronegative character increases from left to right in a period.

(e) Nature of oxides.

Answer: Oxides become less basic and more acidic when we move from left to right in a period. This happens because of reduction in metallic character.

OR

(a) What was the basis of Mendeleev’s classification of elements?

Answer: Atomic mass

(b) List two achievements of Mendeleev’s periodic tables.

Answer: Following are two achievements of Mendeleev’s periodic table:

• Prediction of elements to be discovered in future.
• Correct position of noble gases which were not known during Mendeleev’s time.

(c) List any two observations which posed a challenge to Mandelẽev’s periodic law.

Answer: Following observations posed a challenge to Mendeleev’s periodic law:

• Position of isotopes could not be clarified in Mendeleev’s Periodic Table
• Mendeleev placed many elements in wrong order of their increasing atomic masses in order to place elements having similar properties in similar group.

Question 18:

(a) Write the reaction that occurs when glucose breaks down anaerobically in yeast.

Answer: C_6H_(12)O_6→2C_2H_5OH+2C\O_2

(b) Write the mechanism by which fishes breathe in water.

Answer: Fishes breathe through gills. Gills absorb oxygen (dissolved in water) from water and then oxygen goes to the blood.

(c) Name the balloon likes structures present in lungs. List its two functions.

Answer: Balloon like structures in lungs are called alveoli. Two functions of alveoli are as follows:

• Removal of carbon dioxide from blood
• Addition of oxygen to blood

(d) Name the respiratory pigment and write its role in human beings.

Answer: Haemoglobin is the respiratory pigment and it is responsible for carrying oxygen.

OR

(a) Name the process and explain the type of nutrition found in green plants. List the raw materials required for this process. Give chemical equation for the mentioned process.

Answer: Plants follow autotrophic mode of nutrition and the process by which a green plant makes food is called photosynthesis. The raw materials required for photosynthesis are:

• Carbon dioxide,
• Water
• Sunlight

Chemical Equation for Photosynthesis:

6CO_2+6H_2O→C_6H_(12)O_6+6O_2

(b) Write three events that occur during this process.

Answer: Three events during photosynthesis are as follows:

1. Sunlight activates chlorophyll
2. Splitting of water molecule
3. Reduction of carbon dioxide to make carbohydrate

Question 19:

(a) What is variation? How is variation created in a population? How does the creation of variation in a species promote survival?

Answer: Differences in traits through successive generations are called variations. Variation is created due to some inaccuracies during DNA replication. Chances of variations are higher during sexual reproduction rather than during asexual reproduction. Variations can be either useful or harmful. Useful variations help an organism survive the onslaught of changed environment. Thus, most often useful variations are passed on to the next generation. Thus, variations help in survival of species.

(b) Explain how, offspring and parents of organisms reproducing sexually have the same number of chromosomes.

Answer: Gametes are produced through meiosis. We know that number of chromosomes becomes half after meiosis. Thus, gametes have haploid number of chromosomes. When male and female gametes fuse during fertilization, the number of chromosomes in zygote becomes diploid. This helps in maintaining the number of chromosomes in offspring of sexually producing organisms.

Question 20:

(a) What is presbyopia? State its cause. How is it corrected?

Answer: The power of accommodation of the eye usually decreases with ageing. For most people, the near point gradually recedes away. They find it difficult to see nearby objects comfortably and distinctly without corrective eye-glasses. This defect is called Presbyopia. It arises due to the gradual weakening of the ciliary muscles and diminishing flexibility of the eye lens. Sometimes, a person may suffer from both myopia and hypermetropia. Such people often require bifocal lenses. A common type of bi-focal lenses consists of both concave and convex lenses. The upper portion consists of a concave lens. It facilitates distant vision. The lower part is a convex lens. It facilitates near vision.

(b) Why does the Sun appear reddish early in the morning? Explain with the help of a labelled diagram.

Answer: Red colour scatters the least and hence travels the farthest. During early morning, the sunlight has to travel a longer distance to reach us. During this, the blue colour is scattered almost completely and the sun and the sky appear reddish.

Question 21:

(a) What are magnetic field lines? How is the direction of magnetic field at a point in a magnetic field determined using field lines?

Answer: The imaginary lines of magnetic field around a magnet are called field line or field line of magnet. Outside the magnet, the direction of magnetic field line is taken from north pole to South Pole. Inside the magnet, the direction of magnetic field line is taken from south pole to north pole.

(b) Two circular coils ‘X’ and ‘Y’ are placed close to each other. If the current in the coil ‘X’ is changed, will some current be induced in the coil ‘Y’? Give reason.

Answer: When a conductor is set to move inside a magnetic field or a magnetic field is set to be changing around a conductor, electric current is induced in the conductor. When the current in the coil ‘X’ is changed it changes the magnetic field around ‘X’. Due to this, some current is induced in coil ‘Y’ by way of magnetic induction.

(c) State ‘Fleming’s right hand rule”.

Answer: Fleming’s Right Hand Rule: If the right hand is stretched in a way that the index finger, middle finger and thumb are in mutually perpendicular directions, then the thumb shows the direction of movement of the conductor, index finger shows the direction of magnetic field and the middle finger shows the direction of induced current in the conductor. The directions of movement of conductor, magnetic field and induced current can be compared to three mutually perpendicular axes, i.e. x, y and z axes.

### Section – B

Question 22: In the laboratory of a school, the sample of hard water is not available “to study the comparative cleaning capacity of a sample of soap in soft and hard water”. Which salt from the laboratory can be added to tap water to make it hard? In the experiment how is cleaning capacity of soap compared?

Answer: Salts of calcium and magnesium can be added to tap water to make it hard water. Cleaning capacity of soap is compared by comparing the time it takes the foam to disappear in case of different samples of water.

Question 23: In a school laboratory the students are studying the properties of ethanoic acid through certain experiments. How can they test its acidic nature? Give two tests.

Answer: Acidic nature of ethanoic acid can be tested by following methods:

• By using blue litmus paper: Blue litmus changes to red in presence of acid.
• By using sodium hydroxide to carry out neutralization reaction. If the beaker (containing the reaction mixture) becomes warm, it indicates reaction has taken place.

Question 24: Draw a labelled diagram of the experimental set up for the study of liberation of carbon dioxide gas during respiration.

Answer: Do It Yourself: You can make the diagram of a test tube a straw; showing air being blown by mouth through the straw. Alternately, you can make the diagram of conical flask with germinating seeds kept in it. The flask should be connected to a test tube containing lime water.

Question 25: Draw diagrams showing reproduction in yeast in proper sequence.

Answer: Question 26: While tracing the path of a ray of light passing through a rectangular glass slab a student tabulated his observations. If in his experiment for two readings he takes two values of ∠i as 40 º and 50º, what should be the correct values of ∠e and ∠r in each case?

Answer: We know that emergent ray is parallel to the incident ray in case of light entering a particular medium and exiting it.

So, ∠i=∠e

OR

Draw a labelled ray diagram for the formation of image by a convex lens of focal length 15 cm when the object is placed at a distance of 25 cm from the lens. Determine the size of the image formed, if size of the object is 4 cm.

Answer: Given, u = -25 cm, f = 15 cm

Image distance can be calculated as follows:

1/v-1/u=1/f

Or, 1/v+1/(25)=1/(15)

Or, 1/v=1/(15)-1/(25)

Or, 1/v=(5-3)/(75)=2/(75)

Or, v=(75)/2=37.5 cm

Now, size of image can be calculated as follows:

v/u=(h_2)/(h_1)

Or, (37.5)/(-25)=(h_2)/4

Or, h_2=(37.5)/(-25)xx4=-6 cm

Question 27: You have following material:

An ammeter (0-1A), a voltmeter (0-3V), a resistor of 20 Ω, a key, a rheostat, a battery of 3 V and seven connecting wires.

Using this material draw a labelled circuit diagram to study the dependence of potential difference (V) across a resistor on the current (I) passing through it.

Answer: Do it yourself

CHAPTER LIST