CBSE Sample Papers for Class 10 Science Paper 8
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 8.
Time Allowed: 3 hours
Max. Marks: 80
- 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.
During summer season, a milkman usually adds a very small amount of baking soda to fresh milk. Give one reason.
Dry Hydrogen Chloride gas does not turn blue litmus red whereas Hydrochloric acid does. Give one reason.
A person is able to see objects clearly only when these are lying at distances between 50cm and 300cm from his eye.
- What kind of defects of vision he is suffering from?
- What kind of lenses will be required to increase his range of vision from 25cm to infinity? Explain briefly.
Given below is a picture of an ecosystem. Identify any two abiotic components and any two biotic components of this ecosystem.
Quote three instances where human intervention saved the forests from destruction.
- Why potato chips manufacturers fill the packet of chips with nitrogen gas?
- A student has been collecting silver coins and copper coins. One day she observed a black coating on silver coins and a green coating on copper coins. Which chemical phenomenon is responsible for these coatings? Write the chemical name of black and green coatings.
- Crystals of copper sulphate are heated in a test tube for some time.
- What is the colour of copper sulphate crystals before heating, and after heating?
- What is the source of liquid droplets seen on the inner upper side of the test tube during the heating process?
- A metal ‘X’ when dipped in aqueous solution of aluminium sulphate no reaction is observed whereas when it is dipped in an aqueous solution of ferrous sulphate, the pale green solution turns colourless. Identify metal ‘X’ with reason.
State which of the following chemical reactions will take place, giving suitable reason for each.
Zn (s) + CuSO4 (aq) → ZnSO4 (aq) + Cu (s)
Fe (s) + ZnSO4 (aq) → FeSO4 (aq) + Zn (s)
Zn (s) + FeSO4 (aq) → ZnSO4 (aq) + Fe (s)
What is a homologous series of carbon compounds ? List its any two characteristics. Write the name and formula of next higher homologue of HCOOH.
Label parts 1 to 6 in the given figure of the brain.
- Answer the following:
- Which hormone is responsible for the changes noticed in females at puberty?
- Dwarfism results’ due to deficiency of which hormone?
- Blood sugar level rises due to deficiency of which hormone?
- Iodine is necessary for the synthesis of which hormone?
- Which hormone controls the metabolism of calcium and phosphorus in human beings?
- Give an example of a plant hormone that promotes growth.
Study the given data and answer the questions following the data.
|Parental plants cross fertilised and seeds collected||Ft
(first generation off spring)
(offspring of self pollination
Male parent always bore red flowers.
Female parent always had white flowers.
|330 seeds sown and observed.
All 330 gave red flowers
|Out of 44 seeds, 33 seeds gave plants with red flowers and 11 seeds gave plants with white flowers|
- What is the term for this type of cross?
- What does the data of the column marked F, indicate?
- Express the genotype of the
- F, Progeny and
- F, Progeny
Give one term caption for the two pictures given here.
Define the term and give its signifance in evolution.
Varun instead of copying from the black board used to copy regularly from the note book of his friend, Sudhir with whom he sat on the same desk. Sudhir told the teacher about it. The teacher asked Varun to get his eyes checked by a doctor and explained to whole class the reason why Varun copied from Sudhir’s notebook.
- What in your view is wrong with Varun’s eyes and how can it be corrected?
- If the doctor prescribes Varun to use lenses of power – 0.5 D, write the type of these lenses.
- Write the values displayed by Sudhir and his teacher.
- In a household electric circuit different appliances are connected in parallel to one another. Give two reasons.
- An electrician puts a fuse of rating 5A in that part of domestic electrical circuit in which an electrical heater of rating 1.5 kW, 220 V is operating. What is likely to happen in this case and why? What change, if any, needs to be made?
You are given following current-time graphs from two different sources:
- Name the type of current in two cases.
- Identify any one source for each type of these currents.
- What is the frequency of current in case (b) in India?
- Use above graphs to write two differences between the current in two cases.
- Name two gases, other than carbon-dioxide, that are given out during burning of fossil fuels and contribute towards acid rain formation.
- Out of two solar cookers, one was covered by a plane glass slab and the other was left open. Which of the two solar cookers will be more efficient and why?
- Why are many thermal power plants set up near coal or oil fields?
- Justify in one sentence that hydropower (hydel electricity) is a renewable source of energy.
- A dry pallet of common base ‘X’, when kept in open air absorbs moisture and turns sticky. The compound is also a by-product of chlor-alkali process. Identify ‘X’. What type of reaction occurs when ‘X’ is treated with strong acid? Write a balanced chemical equation for such reaction.
- Can we store the base ‘X’in an aluminium container? Give reason in support of your answer.
- What were the two major shortcomings of Mendeleev’s periodic table? How have these been removed in the modern periodic table?
- Two elements X and Y have atomic numbers 12 and 16 respectively. Write the electronic configuration for these elements. To which period of the modern periodic table do these two elements belong? What type of bond will be formed between them and why?
- Draw the diagram of heart and label its four chambers.
- Construct a table to show the functions of these four chambers.
Plants absorb water from the soil. How does this water reach the tree tops? Explain in detail.
- What is pollination? Give its two types.
- Draw a longitudinal section of female reproductive part of a flower showing germination of pollen grain. Label on it the following:
- Pollen tube with a male germ cell;
- Female germ cell.
Draw ray diagrams to show the formation of a three times magnified
- real image
- virtual image of an object kept in front of a converging lens. Mark the positions of object, F, 2F, O and position of image clearly in the diagram. An object of size 5 cm is kept at a distance of 25cm from the optical centre of a converging lens of focal length 10cm. Calculate the distance of the image from the lens and size of the image.
A current of 1 ampere flows in a series circuit having an electric lamp and a
conductor of 5 Ω when connected to a 10 V battery. Calculate the resistance of the electric lamp. Now ifa resistance of 10Ω is connected in parallel with this series combination, what change (if any) in current flowing through 5 Ω conductor and potential difference across the lamp will take place? Give reason.
B1, B2, B3 are three identical bulbs connected as shown in figure. Ammeters A1, A2, A3 are connected as shown. When all the bulbs glow, the current of 3A is recorded by ammeter A.
- What happens to the glow of the other two | bulbs when bulb B, gets fused?
- What happens to the reading of A1, A2, A3 and A when the bulb B, gets fused?
- How much power is dissipated in the circuit when all the three bulbs glow together?
When an iron rod is dipped into a solution of copper sulphate, copper is displaced. Why is it so?
Iron filings were added to a solution of copper sulphate. After 10 minutes, it was observed that the blue colour of the solution changes and a layer gets deposited on iron filings. What is the colour of the solution and the layer deposited?
While preparing a temporary stained mount of a leaf epidermal peel, how is the extra stain removed?
The given slides A and B were identified by four students I, II III and IV as stated below:
I. Binary fission in Amoeba
Daughter cells of Amoeba
II. Budding in yeast
Buds of yeast
III. Binary fission in Amoeba
Buds of yeast
IV. Budding in yeast
Daughter cells in Amoeba
Of the above mentioned identifications of slides A and B, which one is correct?
Find the focal length of the concave mirror in the experimental set-up shown in figure.
In an experiment to trace the path of a ray of light passing through a rectangular glass slab, angle of incidence in air was given as 60°. Two students P and Q found angle of refraction as 42° and 65° respectively. Who is right and why?
An ammeter has 20 divisions between mark 0 and mark 2 on its scale. Find the least count of the ammeter.
Baking soda is alkaline, so it neutralises the lactic acid present in the milk and prevents its spoilage.
Acids produce hydrogen ions [H+ (aq)] in solution which are responsible for turning blue litmus red. Dry HCl does not give H+ ions in the absence of water.
- The person is suffering both myopia and hypermetropia.
- To correct the vision, the person requires bifocal lenses. Convex lens for seeing near objects from 25 cm to 50 cm and concave lens for seeing farther objects from 300 cm to infinity.
- Abiotic components : Sunlight and soil
- Biotic components : Deer and tree.
The human intervention that saved the forests from destruction are following:
- The ‘Chipko Andolan’ (‘Hug the Trees Movement’) in a remote village called Reni in Garhwal, during the early 1970s.
- Thesal forests of Arabari (in West Bengal) were saved from the degradation with the active and willing participation of the local community.
- Amrita Devi Bishnoi, who in 1731 sacrificed her life along with 363 others for the protection of ‘khejri’ trees in Khejrali village near Jodhpur in Rajasthan.
- Potato chips manufacturers fill the packet of chips with nitrogen gas to prevent the chips from getting oxidised and turn rancid.
- Chemical phenomenon responsible is called Corrosion
Black coating : Silver sulphide (Ag2S)
Green coating : Basic copper carbonate CuCO3Cu(OH)2.
- The colour of copper sulphate crystals before heating is blue and turns white after heating.
- The liquid droplets are actually the water droplets. The source of water droplets is the water of crystallisation of hydrated copper sulphate crystals (CuSO4.5H2O).
- When metal ‘X’ is dipped in aqueous solution of aluminium sulphate no reaction is observed, it means it is less reactive than aluminium. But when it is dipped in ferrous sulphate solution, the solution turns from pale green to colourless, so ‘X’ is more reactive than iron and thus displaces it from its solution.
Therefore, ‘X’ must be zinc. It reacts with ferrous sulphate to form colourless zinc sulphate solution by displacing iron.
Zn(s) + FeSO4(aq) → ZnSO4(aq) + Fe(s)
In activity series, the most reactive metal is placed at the top whereas the
least active metal is placed at the bottom.
- Zn(s) + CuSO4 (aq) → ZnSO4(aq) + Cu(s)
This chemical reaction will take place because Zn is above Cu in the activity series.
- Fe(s) + ZnSO4(aq) → FeSO4 (aq) + Zn(s)
This reaction will not take place because Fe is below Zn in the activity series and cannot displace Zn from its compounds.
- Zn(s) + FeSO4(aq) → ZnSO4(aq) + Fe(s)
This reaction will take place because Zn is above Fe in the activity series.
A group of organic compounds having the same functional group and similar structures in which any two successive members differ by – CH, are called homologous compounds..
- All members have similar chemical properties
- There is gradation in their physical properties.
Next higher homologue of HCOOH is CH3COOH (ethanoic acid)
- human growth hormone
- Parathyroid hormone (parathormone)
- Auxin is the plant hormone that helps in cell elongation and growth of plants.
- The term used for this type of cross is monohybrid cross.
- Since, all the offsprings in the F1 generation have red flowers therefore, red colour of flower is dominant over white colour.
- Genotype of parents : (RR) and (rr)
- Genotype of F1 Progeny : Rr
- Genotype of F2 Progeny : RR, Rr and rr
The one term caption for the two pictures given is fossils. The fossil can be defined as remains (or impressions) of dead animals or plants that lived in the remote past.
Significance of fossils in evolution : Fossils provide the evidence that the present animals (or plants) have been originated from the previous one through the process of continous evolution.
- Varun is suffering from myopia or shortsightedness. This defect can be corrected by using spectacles having concave lenses of appropriate focal length.
- The doctor prescribed Varun Concave lenses
- Teacher is concerned and knowledgeable Sudhir is helpful as well as concerned.
- In parallel connection, if one of the appliance is switched off, or gets fused, there is no effect on the other appliances and they keep on operating.
- In parallel circuits, the same voltage of the mains line is available for all
the electrical appliances.
Power of heater (P) = Voltage (V) × current (I)
Current drawn by heater, I =
Given P=1.5 kW = 1.5 × 103 W, V = 220 V
∴ Current, I =
As fuse connected is rated 5A, it cannot tolerate the current of 6.8 A, so the fuse will blow.
To operate the heater we should put the fuse rating 10 A
- In graph
- current is direct current (dc) while in graph
- current is alternating current (ac)
- For dc, the source is a cell or a battery. For ac, the source is ac generator.
- In India the frequency of alternating current (case b) is 50 Hz
Direct Current Alternating Current Direct current is unidirectional. Alternating current changes its direction periodically. The value of current remains same. The value of current changes.
- Sulphur dioxide and nitrogen oxide contributes towards acid rain other than CO,
- The solar cooker with the plane glass slab will be more efficient; as the heat gets trapped within the cooker the temperature of the cooker rises. On the other hand, in uncovered cooker the heat rays are not trapped within the cooker. Hence, the temperature of the covered cooker rises more than that of uncovered cooker and thus it will be more efficient.
- Coal and petroleum are required to heat up water to produce steam which further runs the turbine to generate electricity in thermal power plants. Cost of transportation is reduced if the thermal power plants are set up near coal or oil fields. Thus, thermal power plants are set up near coal or oil fields
- Hydropower uses water from the reservoir for generating electricity. The reservoir again gets filled whenever it rains or through rivers. Thus, hydropower is renewable source of energy.
- ‘X’is NaOH.
When NaOH is treated with strong acid like HCl, neutralisation reaction occurs and salt is formed.
NaOH + HCI → NaCl + H2O ‘X’Strong acid
- No, ‘X’ cannot be stored in aluminium container because aluminium with a coating of oxide reacts with the NaOH to form a salt and water.
- Two major shortcomings of Mendeleev’s periodic table:
- The position of isotopes could not be explained.
- Wrong order of atomic masses of some elements could not be explained. In the modern periodic table, the elements are arranged in the increasing order of their atomic numbers instead of atomic masses.
- Atomic number of element X = 12
Electronic configuration = 2, 8, 2
Atomic number of element Y = 16
Electronic configuration = 2, 8, 6
The period number of an element is equal to the number of electron shells in its atom. These two elements have 3 electron shells, therefore they belong to 3rd period.
They will form ionic bond because X is a metal and Y is a non-metal. X loses two electrons which will be gained by Y.
|Chambers of the heart||
|Right atrium||Receives deoxygenated blood.|
|Sends deoxygenated blood to the lungs.|
|Right ventricle||Sends deoxygenated blood.|
|Left ventricle||Sends oxygenated blood to aorta for transporting to the body.|
Plants absorb water from the soil in the following steps:
- In xylem tissue, vessels and tracheids of the roots, stem and leaves are interconnected to form a continuous system of water-conducting channels reaching all parts of the plant.
- At the roots, cells in contact with the soil actively take up ions. This creates a difference in the concentration of these ions between the root and the soil.
- Water, therefore, moves into the root from the soil to eliminate this difference.
- This steady movement of water into root xylem creates a column of water which is steadily pushed upwards.
- The stomatal transpiration creates a suction force which pulls water from the xylem cells of roots.
- Pollination-Process of transfer of pollen grains from the anther to the stigma of the same or different flower Two types of pollination – Self-pollination and Cross pollination
Here, u = – 25 cm, f = + 10 cm, h = 5 cm, v = ?, h = ? From the lens formula,
∴ Size of image = 3.33 cm.
The negative sign shows that the image is inverted and hence real
- Let the resistance of the lamp = R1
Resistance of conductor = R2 = 5Ω
Total resistance in series, Rs = R1 + R2
- Now, a resistance of 10 2 is connected in 10 V parallel with the series combination. Therefore, the total resistance of the circuit is given by
Thus, 1 A current will flow through 10 Ω resistor and 1 A will flow through the lamp and conductor of 5 Ω resistance. Hence, there will be no change in current flowing through 5 Ω conductor. Also, there will be no change in potential difference across the lamp.
Resistance of combination of three bulbs in parallel
- When bulb B1 gets fused, the currents in B2 and B3 remain same I2 = I3 = IA, so their glow remains unaffected.
- When bulb B, gets fused, the current in B, becomes zero and currents in B1 and B3 remains I A.
Total current I = 1; + 12 + 13
= 1 + 0 + 1 = 2A
- Current in ammeter A1 = I A
- Current in ammeter A2 = O
- Current in ammeter A3 = I A
- Current in ammeter A = 2A
3. When all the three bulbs are connected.
Power dissipitated, P =
When an iron rod is dipped into a solution of copper sulphate, copper is displaced because iron is more reactive than copper. So, it displaces copper and forms iron sulphate.
The solution of the colour is green and that of the coating is reddish-brown. This is because iron being more reactive than Cu displaces Cu from CuSO4 and forms green coloured solution of FeSO4 and a reddish brown layer of Cu get deposited.
While preparing a temporary stained mount of a leaf epidermal peel, extra stain is removed with the help of the filter paper. The filter paper absorbs the extra starch.
I is correct because in binary fission of Amoeba, nucleus divides first, then the cytoplasm and daughter cells are formed.
When the object is at infinity in front of a concave mirror, its image is formed at the focus of the mirror. So,
Focal length= Distance between the pole and focus
= 33.6 cm – 22.6 cm
= 11.0 cm
When a ray of light goes from air to glass, it bends towards the normal. So, the angle of refraction must be less than angle of incidence. The student P is right. ! Range
Least count =
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