CBSE EXAMINATION PAPER-2023
SCIENCE
(Solved)
General Instructions :
Read the following instructions carefully and follow them :
- This question paper contains 35 questions. All questions are compulsory.
- This question paper is divided into 5 sections.
- Section A – questions number 1 to 1 are case based questions
- Section B – questions number 2 to 13 are multiple choice questions
- Section C – questions number 14 to 22 are very short answer
- Section D – questions number 23 to 31 are short answer
- Section E – questions number 32 to 35 are long answer
- There is no overall choice given in the question paper. However, an internal choice has been provided in few questions.
- Use of calculator is NOT allowed.
Section A
(1) Determine the speed of light in diamond if the refractive index of diamond with respect to vacuum is 2.42. Speed of light in vacuum is 3×10⁸ m/s
(2) Refractive indices of glass, water and carbon disulphide are 1.5, 1.33 and 1.62 respectively. If a ray of light is incident in these media at the same angle (say θ), then write the increasing order of the angle of refraction in these media.
(3) The speed of light in glass is 2×10⁸ m/s and in water is 2.25×10⁸ m/s.
(a) Which one of the two is optically denser and why?
(b) A ray of light is incident normally at the water-glass interface when it enters a thick glass container filled with water. What will happen to the path of the ray after entering the glass? Give reason.
(4) The absolute refractive indices of water and glass are 4/3 and 3/2 respectively.
If the speed of light in glass is 2×10⁸ m/s, find the speed of light in
(i) vacuum and
(ii) water.
Section B
When aqueous solutions of potassium iodide and lead nitrate are mixed, an insoluble substance separates out. The chemical equation for the reaction involved is:
A metal ribbon ‘X’ burns in oxygen with a dazzling white flame forming a white ash ‘Y’. The correct description of X, Y and the type of reaction is:
The name of the salt used to remove permanent hardness of water is:
Observe the following diagram and identify the process and its significance from the following options:
An alpha particle enters a uniform magnetic field as shown. The direction of force experienced by the alpha particle is:
Assertion (A): Reaction of Quicklime with water is an exothermic reaction.
Reason (R): Quicklime reacts vigorously with water releasing a large amount of heat.
Section C
A student took a small amount of copper oxide in a conical flask and added dilute hydrochloric acid to it with constant stirring. He observed a change in colour of the solution.
(i) Write the name of the compound formed and its colour.
(ii) Write a balanced chemical equation for the reaction involved.
Name the part of brain which is responsible for the following actions:
(i) Maintaining posture and balance
(ii) Beating of heart
(iii) Thinking
(iv) Blood pressure
Where are auxins synthesized in a plant? Which organ of the plant shows:
(i) Positive phototropism
(ii) Negative geotropism
(iii) Positive hydrotropism
Write one specific function each of the following organs in relation with excretion in human beings:
(i) Renal Artery
(ii) Urethra
(iii) Glomerulus
(iv) Tubular part of nephron
Observe the following diagram and answer the questions following it :
(i) Identify the defect of vision shown.
(ii) List its two causes.
(iii) Name the type of lens used for the correction of this defect.
The colour of clear sky from the earth appears blue but from the space it appears black. Why ?
Section D
(i) While electrolysing water before passing the current some drops of an acid are added. Why? Name the gases liberated at cathode and anode. Write the relationship between the volume of gas collected at anode and the volume of gas collected at cathode.
(ii) What is observed when silver chloride is exposed to sunlight? Give the type of reaction involved.
(i) Suggest a safe procedure of diluting a strong concentrated acid.
(ii) Name the salt formed when sulphuric acid is added to sodium hydroxide and write its pH.
(iii) Dry HCl gas does not change the colour of dry blue litmus paper. Why?
(i) How does Paramecium obtain its food?
(ii) List the role of each of the following in our digestive system:
(a) Hydrochloric acid (b) Trypsin (c) Muscular walls of stomach (d) Salivary amylase
(i) What is double circulation?
(ii) Why is the separation of the right side and the left side of the heart useful? How does it help birds and mammals?
(i) Why is an alternating current (A.C.) considered to be advantageous over direct current (D.C.) for the long distance transmission of electric power?
(ii) How is the type of current used in household supply different from the one given by a battery of dry cells?
(iii) How does an electric fuse prevent the electric circuit and the appliances from a possible damage due to short-circuiting or overloading?
Section E
(i) Draw the structure of the following compounds : (a) Butanoic acid (b) Chloropentane
(ii) How are structure (i) and structure (ii) given below related to one another ? Give reason to justify your answer.
(iii) Differentiate between saturated and unsaturated carbon compounds on the basis of their general formula.
(i) What happens when a small piece of sodium is dropped in ethanol? Write the equation for this reaction.
(ii) Why is glacial acetic acid called so?
(iii) What happens when ethanol is heated at 443 K in the presence of conc. H₂SO₄? Write the role of conc. H₂SO₄ in this case.
(iv) Write an equation showing saponification.
(i) Name and explain the two modes of asexual reproduction observed in hydra.
(ii) What is vegetative propagation ? List two advantages of using this technique.
(i) How is electric current related to the potential difference across the terminals of a conductor ? Draw a labelled circuit diagram to verify this relationship.
(ii) Why should an ammeter have low resistance ?
(iii) Two V - I graphs A and B for series and parallel combinations of two resistors are as shown. Giving reason state which graph shows (a) series, (b) parallel combination of the resistors.
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