CBSE Class 10 Science Guess Paper 2027

Which of the following options indicates the products formed after breakdown of the glucose in our muscle cells when there is lack of oxygen? A. Ethanol + carbon dioxide + Energy B. Lactic acid + Energy C. Lactic acid + carbon monoxide + Energy D. Carbon dioxide + Water + Energy

Following are the statements about the different parts of the brain. Select the correct statements. (i) The thinking part of the brain is the forebrain. (ii) Centres for smell, hearing, memory, sight are located in forebrain. (iii) Salivation, vomiting, blood pressure are controlled by medulla in the hind brain. (iv) Cerebellum does not control the posture and balance of the body. (A) (i), (ii) and (iii) (B) (ii), (iii) and (iv) (C) (i), (ii) and (iv) (D) (i), (iii) and (iv)

Two pea plants, one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds were crossed with each other which produced F₁ progeny that have only round yellow (RrYy) seeds. When F₁ plants are self-pollinated, the F₂ progeny will have which new combination of characters, as compared to the parents: (i) Round, yellow (ii) Round, green (iii) Wrinkled, yellow (iv) Wrinkled, green. Correct options are: (A) (i) and (ii) (B) (i) and (iv) (C) (ii) and (iv) (D) (i) and (iii)

Explain why food chains generally consist of three or four steps.

[case context] Plants show movements in response to environmental stimuli regulated by plant hormones. What role does auxin play in the growth of plants?

Given below are some of the statements regarding our environment: (i) Change in our life-styles have resulted in greater amounts of waste material generation. (ii) Changes in attitude have resulted in use of more disposable things. (iii) Changes in packaging has resulted in much of our waste becoming non-biodegradable. (iv) Organic farming. Which amongst these is not leading to any damage of environment? (A) (i), (ii), (iii) (B) (iv) (C) (i) and (iii) (D) (ii) and (iv)

In human beings the oxygen rich blood is pumped out to the body by: (A) contraction of right atrium (B) relaxation of left ventricle (C) contraction of right ventricle (D) contraction of left ventricle

Assertion (A): Tallness of a pea plant is controlled by an enzyme. Reason (R): The gene for that enzyme makes proteins which help the plant to be tall. Options: A. Both A and R are true, and R is the correct explanation of A. B. Both A and R are true, and R is not the correct explanation of A. C. A is true but R is false. D. A is false but R is true.

Assertion (A): The number of chromosomes in a cell and in a germ cell is not the same in any species. Reason (R): When 2 germ cells combine they restore the normal number of chromosomes in a species. [Options: A. Both A and R are true, and R is the correct explanation of A. B. Both A and R are true, and R is not the correct explanation of A. C. A is true but R is false. D. A is false but R is true]

Draw labelled diagrams to show different stages of budding in Hydra.

Assertion (A): Highest percentage of pesticides is found in tertiary consumers in a food chain. Reason (R): Chemicals / pesticides get accumulated progressively at each trophic level. (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A). (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A). (C) Assertion (A) is true, but Reason (R) is false. (D) Assertion (A) is false, but Reason (R) is true.

[case context] Neha consumed boiled sweet potatoes and boiled eggs for breakfast; questions explore steps in the digestion of this food. Attempt either subpart A or B. A. Which of these food items is rich in proteins? In which part of the alimentary canal is the digestion of this component initiated? Name the enzymes, conditions required and the glands associated with the digestion here.

Study the given table and answer the following questions: [Parents: A pea plant with red flowers was crossed with a pea plant with white flowers. | F₁: 30 seeds were sown and all bore plants with red flowers. | F₂: 44 seeds were sown, 33 plants bore red flowers and 11 plants bore white flowers.] (a) Depict the information given in the table in the form of a cross. (b) Deduce the F₂ phenotypic ratio / F₂ ratio showing external look as well as genotypic/genetic makeup, ratio.

Puneet wanted to grow banana plants. (i) Based on your knowledge on plant reproduction should he opt for seeds or any alternate method of reproduction? Justify your answer. (ii) Offsprings of a banana plant usually show very little variation. What causes variation and are variations good or bad? Justify.

Explain the mechanism by which the water is transported in plants.

[Case: Maintenance functions require energy from food prepared by autotrophs.] State in proper sequence the events that occur in synthesis of food by desert plants.

[case context] pH scale predicts strength of acids and bases via hydrogen ion concentration. Three solutions A, B and C showed pH as 3, 5 and 7. Which solution has the highest concentration of H^+ ions?

C₆H₁₂O₆(aq) + 6O₂(g) -> 6CO₂(g) + 6H₂O(l). The above reaction is an example of - (A) Displacement Reaction (B) Endothermic Reaction (C) Exothermic Reaction (D) Neutralisation Reaction

Four statements about the reactions of oxides with dilute hydrochloric acid and aqueous sodium hydroxide are listed. I. Aluminium oxide reacts with both dilute hydrochloric acid and aqueous sodium hydroxide. II. Calcium oxide reacts with dilute hydrochloric acid and aqueous sodium hydroxide. III. Zinc oxide reacts with both dilute hydrochloric acid and aqueous sodium hydroxide. IV. Sulphur dioxide does not react with either dilute hydrochloric acid or aqueous sodium hydroxide. Which statements are correct? A. I and II B. I and III C. II and IV D. III and IV

An iron nail is added to each of the two test tubes 'P' and 'Q' containing aqueous copper (II) sulphate, and aqueous silver nitrate respectively. Which of the following observation is correct? A. In test tube 'P' iron nail is coated with a blue coating and in test tube 'Q' there is no reaction. B. Iron nail is coated with a brown coating in test tube 'P' and silver coating in test tube 'Q'. C. There is no reaction in either of the test tubes 'P' or 'Q'. D. There is no reaction in test tube 'P' but a silver coating on iron nail is seen in test tube 'Q'.

An aqueous solution turns red litmus blue. Excess addition of which of the following solution would reverse the change? (A) Sodium hydroxide (B) Hydrochloric acid (C) Baking soda (D) Slaked lime

Identify 'p', 'q' and 'r' in the following balanced reaction: p Pb(NO₃)₂(s) --Heat--> q PbO(s) + r NO₂(g) + O₂(g) A. 2,2,4 B. 2,4,2 C. 2,4,4 D. 4,2,2

Carbon compounds: (i) are good conductors of electricity. (ii) are bad conductors of electricity. (iii) have strong forces of attraction between their molecules. (iv) have weak forces of attraction between their molecules. The correct statements are: (a) (i) and (ii) (b) (ii) and (iii) (c) (ii) and (iv) (d) (i) and (iii)

Assertion (A): C₄H₈, C₄H₆ and C₄H₁₀ are members of the same homologous series. Reason (R): C₄H₈, C₄H₆, C₃H₄, C₃H₆, C₂H₄, C₂H₂ are unsaturated hydrocarbons. Options: A. Both A and R are true, and R is the correct explanation of A. B. Both A and R are true, and R is not the correct explanation of A. C. A is true but R is false. D. A is false but R is true.

(i) Which method will be used to convert each of them to their respective metal oxides? (a) Carbonate ore (b) Sulphide ore. (ii) Write a chemical reaction to illustrate the use of aluminium for joining cracked railway tracks. (iii) During extraction of metals, electrolytic refining is used to obtain pure metals. Which material will be used as anode and cathode for the refining of copper metal by this process?

[case context] Sara added phenolphthalein to 2 mL dilute NaOH (turned pink), then added dilute H₂SO₄ drop by drop until colourless (40 drops needed); a drop of NaOH turned it pink again. Table: 2 mL NaOH -> 20 drops H₂SO₄; 3 mL -> 30 drops; 4 mL -> 40 drops. A. If Sara used concentrated H₂SO₄ in place of dilute H₂SO₄, how many drops will be required for the change in colour to be observed? (a) 40 (b) < 40 (c) > 40. Justify your answer.

An element 'X' is stored in kerosene, and cannot be extracted from its ore using a reducing agent. 'X' forms an ionic compound on reaction with chlorine. (i) Can we store 'X' in water? Give reason to support your answer. (ii) Identify element 'X'. Name the process used and write the equation for extraction of 'X' from its ore.

The electronic structures of atoms P and Q are shown in the given figure. Based on the information given above, answer the following questions: (a) If P and Q combine to form a compound, what type of bond is formed between them? (b) Give the chemical formula of the compound formed. (c) The compound so formed is dissolved in water. Is the resultant solution acidic or basic in nature? Justify your answer. (d) Write the chemical equation for the reaction between 'Q' and ethanol. (e) What will be the formula of the compound formed when 'P' undergoes bonding with carbon?

(i) A carbon compound X is a good solvent. On reaction with sodium, X forms two products Y and Z. Z is used to convert vegetable oil into vegetable ghee. Identify and name X, Y and Z. Also write the equation of reaction of X with sodium to justify your answer. (ii) Write chemical equation to show what happens when ethanol: (I) burns in oxygen/air. (II) is heated at 443 K in excess conc. H₂SO₄. (III) reacts with acidified potassium dichromate.

Arnav was making notes and he wrote down the following statements from his understanding of reflection from curved surfaces. I. Concave mirrors can produce both real and virtual images depending on the position of the object. II. Convex mirrors always produce real, inverted images regardless of the object's position. III. In both concave and convex mirrors, the image location can be determined using the mirror formula 1/f = 1/v + 1/u where f is the focal length, v is the image distance, and u is the object distance. Choose from the following the correct option that lists the correct statements about reflection from curved surfaces. A. I and II B. I, II and III C. II and III D. I and III

Choose the correct option from the below which explains the reason for us to perceive the day sky as blue. A. As sunlight passes through the atmosphere, shorter wavelengths, such as blue are scattered more than other colors. B. The sky appears blue because all colors are scattered equally, but blue light is stronger and more visible to the human eye. C. The blue color of the sky is due to longer wavelengths like red and orange scattering more than shorter wavelengths, making blue stand out more. D. The atmosphere contains blue-colored particles that give the sky its blue appearance.

Assertion (A): No two magnetic field lines are found to cross each other. Reason (R): The compass needle cannot point towards two directions at the point of intersection of two magnetic field lines. Select the correct answer: (A) Both A and R are true and R is the correct explanation of A. (B) Both A and R are true, but R is not the correct explanation of A. (C) A is true, but R is false. (D) A is false, but R is true.

The given figure shows the formation of an image with an optical instrument (shown schematically as a rectangle); an upright object forms an image with the distances 10 cm and 20 cm marked. A. Identify the optical instrument (shown schematically as a rectangle) in the image. B. What type of image is formed in this case? C. Based on the measurements given in the image, calculate the focal length of the instrument. (For visually impaired students: A. Under what conditions can a convex lens form a virtual image? B. Why does a piece of paper catch fire if we allow sunlight to pass through a convex lens onto the paper?)

The given figure shows a corrective measure for a particular defect of vision. (i) Identify the defect of vision and state what kind of lens is used to correct this deficiency. (ii) Draw and label a ray diagram that shows the defect of vision in the above case before correction. (For visually impaired students: (i) What is dispersion of light? (ii) Explain the condition under which dispersion happens? (iii) Give one reason that causes presbyopia.)

(i) The given electric circuit is a part of an electrical device. Use the information given in the electric circuit diagram to calculate: (I) Potential difference across the ends of resistor R₂. (II) Value of resistor R₂. (III) Value of resistor R₁. [Circuit data: 12 V source with key K; branch with R₁; a 4.0 Ohm resistor carrying 1.5 A; resistor R₂ in parallel; a 2.0 Ohm resistor; total line current 2.0 A.] (ii) Write the factors on which resistance of a conductor depends and derive the formula for resistance of a given conductor.

Find out the following in the electric circuit given in the figure (an 8 V cell in series with a 4 ohm resistor and ammeter A₁, connected to two 8 ohm resistors joined in parallel between points C and D, with ammeter A₂ in the return path): (i) Effective resistance of two 8 ohm resistors in the combination. (ii) Current flowing through the 4-ohm resistor.

On the basis of the given circuit arrangement, answer the following questions: (a) What happens to the rod AB when the key K is closed and why? (b) Name and state the rule that determines this behaviour of the rod AB in the above situation.

(i) How much electric current will an electric iron draw from 220 V source if the resistance of its heating element when hot, is 55 Ohm? Calculate the power consumed by the electric iron when it is operated at 220 V. (ii) In a house, 3 bulbs of 100 watt each, are lit for 5 hours daily and an electric heater of 1.0 kW is used for half an hour daily. Calculate the total energy consumed in a month of 30 days and its cost at the rate of Rs. 3.60 per kWh. (iii) With reason explain, why are alloys commonly used to make elements of electrical heating devices.

(a) Write the relationship between resistivity and resistance of a cylindrical conductor of length l and area of cross-section A. Hence derive the SI unit of resistivity. (b) Why are alloys used in electrical heating devices ?