CBSE Sample Papers for Class 10 Science Paper 12

These Sample papers are part of CBSE Sample Papers for Class 10 Science. Here we have given CBSE Sample Papers for Class 10 Science Paper 12.

CBSE Sample Papers for Class 10 Science Paper 12

Board	CBSE
Class	X
Subject	Science
Sample Paper Set	Paper 12
Category	CBSE Sample Papers

Students who are going to appear for CBSE Class 10 Examinations are advised to practice the CBSE sample papers given here which is designed as per the latest Syllabus and marking scheme as prescribed by the CBSE is given here. Paper 12 of Solved CBSE Sample Paper for Class 10 Science is given below with free PDF download solutions.

Time Allowed: 3 hours
Max. Marks: 80

General Instructions:

• The question paper comprises two sections, A and B. You are to attempt both the sections.
• All questions are compulsory.
• All questions of Section-A and B are to be attempted separately.
• There is an internal choice in three questions of three marks each, two questions of five marks each and one question
• (for assessing the practical skills) of two marks.
• Question numbers 1 and 2 in Section-A are one mark question. They are to be answered in one word or in one sentence.
• Question numbers 3 to 5 in Section- A are two marks questions. These are to be answered in 30 words each.
• Question numbers 6 to 15 in Section-A are three marks questions. These are to be answered in about 50 words each.
• Question numbers 16 to 21 in Section-d are five marks questions. These are to be answered in 70 words each.
• Question numbers 22 to 27 in Section- B are based on practical skills. Each question is a two marks question. These are to be answered in brief.

SECTION-A

Question 1.
Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example.

Question 2.
Write the molecular formula of the 2nd and the 3rd member of the homologous series whose first member is methane.

Question 3.
After rains, during day time a rainbow often appears in the sky. Explain how this natural phenomenon occurs, with the help of a diagram.

Question 4.

• “Forests are biodiversity hotspots”. Give reason to justify this statement.
• State the meaning of ‘Sustainable Development’.

Question 5.
Which natural resource are the ‘biodiversity hotspots’? Suggest what happens when there is a loss of biodiversity?

Question 6.
2 g of lead nitrate powder is taken in a boiling tube. The boiling tube is heated over a flame. Now answer the following:

• State the colour of the fumes evolved and the residue left.
• Name the type of chemical reaction that has taken place stating its balanced chemical equation.

Question 7.
Mrs Sharma has gone to the jewellers shop to buy gold jewellery. She asks the jeweller, if the jewellery is made of pure gold. The jeweller assure her that it is 100% gold and nothing has been mixed in it. Mrs Sharma is happy and buys the necklace. Answer the following questions based on the above situation:

• Was the jeweller right in saying that the necklace is made of 100% gold?
• What values are promoted by the jeweller?
• What precautions should you take, while purchasing gold jewellery?
• Why does Government insist on purchasing Hallmarked jewellery?

Question 8.
Write the name and molecular formula of an organic compound having its name suffixed with ‘-ol and having two carbon atoms in the molecule. With the help of a balanced equation indicate what happens when it is heated with excess of conc. H₂SO₄.

OR

1. Name the following:
   • Third member of aldehyde series.
   • Second member of carboxylic series.
2. Write the IUPAC name of the following:
   

Question 9.
How do auxins help in bending of stem towards light? Explain.

OR

Draw a diagram of human brain and label on it cerebrum and cerebellum. State the role of cerebellum.

Question 10.

• Why are testes located outside the abdominal cavity in a sac called scrotum?
• What are secondary sexual characters in humans? Name one such character of male and female.

Question 11.
“The traits acquired during the lifetime of an individual are not inherited”. Give reason and justify this statement giving two examples.

Question 12.
What is colour-blindness? What kind of retinal cells are lacking in person suffering from this defect?

Question 13.
Describe with the help of a diagram, an activity to show that a current carrying wire behaves like a magnet.

Question 14.
Explain briefly two different ways to induce current in a coil. State the rule which determines the direction of induced current.

Question 15.
State two major constituents of biogas. List any four characteristics of biogas on account of which it is considered an ideal fuel.

OR

What is meant by nuclear waste ? State the main hazard of this waste on the living beings. How is this waste disposed off ?

Question 16.

1. Study the following chemical equation:
   
   Name the reactant and the product. State one use of the product.
2. State in tabular form the name of the acid and base from which the following salts are formed. Also mention the nature of the salt, whether it is acidic or basic?
   • Sodium acetate
   • Ammonium sulphate

OR

1. Explain the following chemical properties of acids with the help of balanced chemical equations only.
   • When an acid reacts with a metal carbonate.
   • When an acid reacts with a metal bicarbonate.
   • When an acid reacts with a metal oxide.
2. You are given three solutions A, B and C with pH values 2, 10 and 13 respectively. Write which solution has more hydrogen ion concentration among the three and state the nature ‘acidic or basic’ of each solution.

Question 17.

1. • State the Modern periodic law.
   • What is the total number of periods and groups in Modern Periodic Table.
2. From the part of a periodic table, answer the following questions:
   
   • Atomic number of oxygen is 8. What would be the atomic number of fluorine?
   • Out of ‘X’ and ‘Q’ which element has larger atomic size? Give reason for your answer.
   • Out of ‘Y’ and ‘Z’ which element has smaller atomic size? Give reason for your answer.

Question 18.

1. Draw the diagram of sectional view of human heart and label on it
   • Chamber which receives deoxygenated blood from vena cava.
   • Chamber which pumps oxygenated blood into Aorta.
   • Blood vessel which brings oxygenated blood to the heart.
   • Chamber which receives oxygenated blood from lungs.
2. What is double circulation of blood ?

OR

1. Draw a diagram of human alimentary canal and label on it:
   • Organ which stores bile
   • Organ which produces bile
2. Name one enzyme present in pancreatic juice and give its functions.
3. What are peristaltic movements ?

Question 19.

1. Explain why does menstruation occur in human females?
   • Mention the two functions of ovaries in human female reproductive system.
   • Mention the name of organ
     • that provides nutrition to embryo.
     • site where fertilised egg gets implemented.

Question 20.

1. The absolute refractive index of water is 4/3. What is meant by this statement?
2. A pencil partially immersed in water appears to be bent. Name the phenomenon responsible for this observation and explain it on its basis.
3. An object is placed at a distance of 25m from a concave mirror of focal length 10m. Find the nature and position of the image so formed.

Question 21.

• What is heating effect of current ? List two electrical appliances which work on this effect?
• An electric bulb is connected to a 220 V generator. If the current drawn by the bulb is 0.50 A, find its power.
• An electric refrigerator rated 400 W operates 8 hours a day. Calculate the energy consumed per day in kWh.
• State the difference between kilowatt and kilowatt hour.

SECTION-B

Question 22.
A student took four test tubes I, II, III and IV containing aluminium sulphate, copper sulphate, ferrous sulphate and zinc sulphate solutions, respectively. He placed an iron strip in each of them. In which test tube, a · brown deposit is formed?

Question 23.
On adding zinc granules to freshly prepared ferrous sulphate solution, what is observed?

Question 24.
Why was the temporary mount of the leaf epidermal peel pinkish-red under the microscope?

Question 25.
Students were asked to observe the permanent slides showing different stages of budding in yeast under high power of a microscope.

• Which adjustment screw (coarse/fine) were you asked to move to focus the slides?
• Draw three diagrams in correct sequence showing budding in yeast.

Question 26.
To find the image distance for varying object-distances in case of a convex lens, a student obtains on a screen a sharp image of a bright object placed very far from the lens. After that he gradually moves the object towards the lens and each time focuses its image of the screen.

• In which direction towards or away from the lens, does he move the screen to focus the object?
• What happens to the size of image—does it increase or decrease?
• What happens when he moves the object very close to the lens?

OR

You are given a convex lens of focal length 30 cm. At what distance from the lens should you hold a candle flame to observe a virtual image of the flame?

Question 27.
In an experiment to study the dependence of current on potential difference across a resistor, a student obtained the graph as shown in the diagram.

Find the value of resistance of the resistor?

Answers
SECTION-A

Answers 1.
When a metal reacts with an acid, usually hydrogen gas is liberated. For example, zinc reacts with dilute sulphuric acid as follows:
Answers 2.
C₂H₆, C₃H₈

Answers 3.
Due to dispersion and internal reflection small drops of water act like a prism and a rainbow is formed.
Answers 4.

• Forests are considered biodiversity hotspots because a large number of plant and animal species are found here.
• Sustainable development is the form of growth that meets current basic human needs while preserving the resources for future generations.

Answers 5.
Forests are the ‘biodiversity hot spots’. If there is a loss of biodiversity, there will be imbalance in ecological stability leading to extinction of species.

Answers 6.

• Brown fumes of NO, gas are evolved and white residue of lead oxide is left.
• Decomposition reaction takes place.
  2Pb (NO₃)₂ → 2Pb0 + 4NO₂ + O₂

Answers 7.

1. No, he was wrong. Pure gold is very soft and is, therefore, not suitable for making jewellery. It is alloyed with either silver or copper to make it hard. But, sometimes jewellers mix a large quantity of copper and silver in gold, to earn more profit.
2. Untrustworthiness, cheating, cunning.
3. We should always purchase the gold jewellery from a branded shop with proper receipt and Hallmark certificate.
4. Government insists on purchasing hallmarked jewellery as it contains the gold and its alloyed metal (i.e., copper or silver) in a fixed ratio.

Answers 8.
The organic compound is ethanol. Its molecular formula is C₂H₆O and structural formula is C₂H₅OH or CH₃CH₂OH. When it is heated with excess of conc. H₂SO₄, ethene is formed.

OR

1. • Propanal (CH₃CHO)
   • Ethanoic acid (CH₃COOH)
   • 2, 2-dimethyl propane
   • 2-butanol

Answers 9.
When growing plants detect light, a hormone called auxin, synthesised at the shoot tip helps the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light. Thus plant appears to bend towards light.

OR

1.
Cerebellum. It is responsible for precision of voluntary actions and maintaining posture and balance of the body.

Answers 10.

1. Testes are placed outside the body cavity in the scrotal sac because it requires a temperature 2°C lower than the normal body temperature for production of sperms.
2. Characters which distinguish a male from female are called secondary sexual characters.! Secondary sexual characters of male are moustache, beard, thick growth of hair on body, strong muscles and harsh voice. (Any one) Secondary sexual characters of female are less hair on body, broad hips, development of breasts and soft voice. (Any one)

Answers 11.
Certain changes occur in the structure or function of the body parts due to environmental factors. Such changes in somatic tissues are acquired traits that do not involve germ cells and genetic material (DNA). Therefore, these changes are not passed to the next generation. The traits are only inherited if changes take place in the genetic material. Examples: starving beetles and surgical removal of tail in mice.

Answers 12.
The defect of the eye due to which a person is unable to distinguish between certain colours, is known as colour blindness. Cone shaped retinal cells are responsible for making a person differentiate between colours. The colour blind persons do not possess cone cells that respond to certain colours.

Answers 13.

• Take a straight thick copper wire and place it between points X and Y in an electric circuit.
• Place a small compass near this copper wire
• As we pass current through the copper wire XY, the compass needle gets deflected.

Conclusion: Since a magnetic needle can be deflected only by a magnetic field so we can say that a current carrying wire behaves like a magnet.

Answers 14.
Two ways to induce current in a coil are

• If a coil is moved in a magnetic field
• By bringing a bar magnet close to the coil or taking it away from the coil.
• By rotating the coil in a uniform magnetic field.

The direction of induced current is determined by Fleming’s Right Hand rule which states that “If we stretch the forefinger, middle finger and thumb of our right hand in such a way that thumb points along the direction of motion of conductor, forefinger along the direction of magnetic field; then
the middle finger points along the direction of induced current.

Answers 15.
Methane, carbon dioxide, hydrogen, hydrogen sulphide are the major constitutents of biogas. (Any two) Four characteristics that makes biogas an ideal fuel:

• It can burn without smoke.
• It does not produce any ash.
• It can be used directly for heating, lighting and generating electricity.
• Slurry left behind in a biogas plant is used as manure rich in nitrogenous and phosphorous compounds.

OR

1. The discarded material of nuclear industry such as remains of the radioactive products of nuclear reactions is called nuclear waste.
2. The main hazard is waste materials possess radioactive rays which emit particles which can damage man, animal and plant tissues.
3. Nuclear wastes have to be buried deep inside the earth for disposing it off.

Answers 16.

• Reactant — Gypsum
  Product — Plaster of Paris

Use : Healing the fractured bones, casting moulds for statues or toys, dentistry

Salt	Acid	Base	Nature
Sodium acetate Ammonium sulphate	Acetic acid Sulphuric acid	Sodium hydroxide Ammonium hydroxide	Basic Acidic

OR

1. • 2HCl + Na₂ CO₃ – 2NaCl + H₂O + CO₂
   • HCl + NaHCO₃ — NaCl + H₂O + CO₂
   • 2HCl + CaO → CaCl₂ + H₂O
2. A has higher hydrogen ion (H+) concentration as it as lowest pH value.
   A is acidic.
   B and C are basic in nature.

Answers 17.

1. • According to Modern Periodic Law, properties of elements are a periodic function of their atomic number.
   • Periods—7 and groups—18
   • 9, because atomic number increases by one in going from one element to the next in Modern Periodic Table.
   • ‘X’ has larger atomic size because atomic size decreases along a period due to increase in effective nuclear charge.
   • ‘Y’ has smaller atomic size because new shells are added when we go down the group.

Answers 18.

1. • Right atria
   • Left ventricle
   • Pulmonary vein
   • Left atria
2. Blood that goes through the heart twice during each cycle is called double circulation of blood.

OR

1. • Gall bladder
   • Liver
2. Trypsin is one of the enzyme of pancreatic juice. It breaks down dietary protein molecules to their component peptides and amino acids.
3. The lining of alimentary canal has muscles that contract rhythmically in order to push food forward. These are called as peristaltic movements.

Answers 19.

1. Every month uterus prepares itself to receive fertilised egg. Its lining becomes thick to provide nutrition to embryo if fertilisation of egg takes place. If fertilisation of egg does not take place then lining is no longer needed and it get detached and comes out through vagina in the form of menstruation.
   • Functions of ovaries:
     • Production of female gamete (ovum) 9001 )
     • Secretion of female hormones. (progesterone + estrogen)
     • placenta
     • uterus

Answers 20.

1. Absolute refracture index of water means that ratio of speed of light in air to ratio of speed of light in water. i.e.,
   
2. Due to refraction rays coming from immersed part of pencil are refracted at interface and appear to come from different part due to which pencil partially immersed, appears to be bent.
3. 

The image formed will be real and inverted.

Answers 21.

1. The phenomenon of production of heat in a resistor by the flow of an electric current through it is called heating effect of current. Heating element of geyser, heater, filament of bulb work on this principle.
2. 
3. kilowatt is unit of power and kWh is unit of electrical energy.

SECTION-B

Answers 22.
A brown deposit is formed in test tube II because iron being less reactive does not displace metals from the solution of Al(SO₄)₃, FeSO₄ and ZnSO₄ but it is more reactive than Cu. So, it displaces copper from CuSO₄ and forms FeSO₄ which is green in colour and a brown deposit of copper metal.

Answers 23.
It is observed that the solution turns from green to colourless and a black coating is formed. This is because zinc being more reactive than iron displaces it from FeSO₄ and forms colourless solution of ZnSO₄ along with a black coating of Fe.

Answers 24.
The temporary mount of the leaf epidermal peel was pinkish-red under the microscope because it was stained in safranin and safranin is pinkish-red in colour.

Answers 25.

1. The fine adjustment screw is moved to focus the slides.
2. In budding, one or more outgrowths appear on one side, which enlarges in size. The nucleus divides mitotically, one daughter nucleus passes into the bud and the other remains in the parent cell. The bud either separates off from the parent cell or new bud appears before its separation from the parent cell resulting in the formation of branched or unbranched chain of buds.
   

Answers 26.

• He moves the object away from the lens.
• The size of image increases.
• When he moves object very close to lens no image is formed on the screen.

OR

When the object is placed within the focus of a convex lens, the image formed is virtual, erect and magnified. Hence, the candle flame must lie between 0 to 30 cm from the lens to observe the virtual image.

Answers 27.

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