CBSE EXAMINATION PAPER-2025
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 2 are case based questions
- Section B – questions number 3 to 16 are multiple choice questions
- Section C – questions number 17 to 23 are very short answer
- Section D – questions number 24 to 29 are short answer
- Section E – questions number 30 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
Many pure metals like copper, iron and gold are very soft and as such are considered unsuitable for certain uses. Metallic objects around us such as cooking utensils, statues, ornaments, guns etc. are actually not made up of pure metals. Instead of pure metals, alloys are used in the design of most of the useful objects. Making alloys enhances the basic properties of a metal which is the primary constituent (metal) of an alloy.
(1) Name an alloy used for welding two wires together in an electric circuit. Write its major constituents.
[1 Marks](2) How does electrical conductivity and melting point of a metal change when it is converted to its alloy by mixing a small amount of an element in it?
[1 Marks](3) What is stainless steel ? How is it prepared ? Write one important property which makes it more useful in making cooking utensils as compared to its primary metal.
(4) What are alloys ? How is ‘Brass’ (an alloy) prepared ?
(1) Name the movement which causes ‘X’ and ‘Y to grow downwards and upwards respectively. (Refer above figure)
(2) Write the name of a hormone that plays a major role in (i) falling of leaves (ii) rapid cell division
(3) Leaves of the sensitive plant move very quickly in response to ‘touch’. How is this stimulus of touch communicated and explain how the movement takes place.
(4) Name the plant hormone which is synthesized at the shoot tip. How does this hormone helps the plant to bend towards light ?
Section B
You have three aqueous solutions A, B and C as given below:
A – Potassium nitrate
B – Ammonium chloride
C – Sodium carbonate
The ascending order of the pH of these solutions is:
Select from the following a statement which is not true about burning of magnesium ribbon in air :
The colour of the solution observed after about 1 hour of placing iron nails in copper sulphate solution is
Juice of tamarind turns blue litmus to red. It is because of the presence of a chemical compound called
The water of crystallization is present in
(i) Bleaching Powder (ii) Plaster of Paris (iii) Washing Soda (iv) Baking Soda
A tall pea plant with round seeds (TTRR) is crossed with a short pea plant with wrinkled seeds (ttrr). The F₁ generation will be:
A pair of endocrine glands located in the human brain is
The basic filtration unit of the excretory system in human beings is :
In human alimentary canal, the digestive juice secreted by the gastric glands are
The part of human eye which controls the amount of light entering into it.
Consider the following food chain:
Grass → Grasshopper → Frog → Snake → Eagle
If the amount of energy available at third trophic level is 50 kJ, the available energy at the producer level was:
Assertion (A) : Carbon and its compounds are our major sources of fuels.
Reason (R) : Most of the carbon compounds on burning release a large amount of heat and light.
Assertion (A): In the common domestic circuits the earth wire is connected to a metallic plate buried deep inside the earth.
Reason (R) : Earth wire ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, so the user may not get a severe electric shock.
Assertion (A) : Food web is a network of several food chains operating in an ecosystem.
Reason (R) : Food web decreases the stability of an ecosystem.
Section C
A light green coloured solution of sulphate salt of metal ‘P’ is taken in a beaker, a rod of another metal “Q’ is put in this solution as shown the following figures :
Identify the metals ‘P’ and ‘Q’ and write its chemical equation for the reaction that occurs. State the conclusion of this reaction in terms of reactivity series of metals.
(a) How is brain protected in our body ?
(b) A doctor finds in one of his patients that he is not maintaining a proper posture and balance of his body. State the region of brain and also the part of brain which is responsible for it.
“Proteins control the expression of various characters.” Explain this statement by taking an example of “tallness” as a characteristic in plants.
Explain the mechanism of inheritance used by sexually reproducing organisms to ensure the stability of DNA of the species.
Study the figure in which the path of a ray of light going from Medium 1 to Medium 2 is shown.
(a) Out of the two Media — Medium 1 and Medium 2, in which is the speed of light more ?
(b) State reason of bending of the refracted ray away from the normal.
(c) Express refractive index of Medium 2 with respect to Medium 1 in terms of speed of light in two media.
Section D
State the chemical property in each case on which the following uses of baking soda are based upon:
(i) as an anti-acid,
(ii) as a constituent in making baking powder,
(iii) in soda-acid fire extinguishers.
Write chemical equations to show what happens when an acid reacts with
(i) metal,
(ii) base,
(iii) carbonate.
Write the name of the main product formed in each case.
A student placed a candle flame at different distances from a convex lens and focused its image on a screen. He recorded his observation in tabular form as given below :
Analyse the observation table and on the basis of your analysis only, answer the following questions (without doing any calculations) :
(a) What is the focal length of the convex lens used ? Give reason to justify your answer.
(b) Which one of the sets of observations is not correct and why ?
(c) Draw ray diagram to show image formation for any correct set of observation.
A person uses lenses of +2.0 D power in his spectacles for the correction of his vision.
(a) Name the defect of vision the person is suffering from.
(b) List two causes of this defect.
(c) Determine the focal length of the lenses used in the spectacles.
(a) Explain the statement “Potential difference between two points is 1 volt”.
(b) What do the symbols given below represent in an electric circuit ? Write one function of each.
Section E
Name an alcohol and a carboxylic acid having two carbon atoms in their structures. Draw their structures and state how this alcohol can be converted into a carboxylic acid. What happens when these two compounds react in the presence of an acid ? Write chemical equations for the reactions involved in the two cases mentioned above.
(a) Define Puberty. List any two changes seen in boys at the time of puberty.
(b) Why are testes in human males located outside the abdominal cavity in scrotum ?
(c) List any three techniques of contraception used by humans. Which one of these is not meant for males ?
(a) Name the part performing following functions in human female reproductive system :
(i) production of eggs
(ii) site of fertilization
(iii) site of implantation
(iv) entry of the sperms
(b) What changes are observed in the uterus :
(i) subsequent to implantation of zygote and
(ii) if an egg does not get fertilized ?
What are soaps ? Write the structure of a soap molecule. Explain the cleansing action of a soap. Why are soaps not considered suitable for washing clothes in a region where water is hard ? How is this problem overcomed ?
What are magnetic field lines ? How is the direction of magnetic field at a point determined ? Draw the pattern of magnetic field lines of the magnetic field produced by a current carrying circular loop. Mark on it the direction of (i) current and (ii) magnetic field lines.
Name the two factors on which the magnitude of the magnetic field due to a current carrying coil depends.
Why can’t two magnetic field lines cross each other ? Draw magnetic field lines showing the direction of the magnetic field due to a current carrying long straight solenoid. State the conclusion which can be drawn from the pattern of magnetic field lines inside the solenoid.
Name any two factors on which the magnitude of the magnetic field due to this solenoid depends.
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