Note: The below solutions have been prepared in concise language to suit my Govt school children. Plus the answers have been added to respective units wherever necessary.
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| JKBOSE Class 10th 2025 Bi-Annual Science Solved Paper |
SECTION-A (1 Marks Each)
Q. The stars twinkle due to atmospheric:
(a) Dispersion of light
(b) Refraction of light (c) Interference of light (d) Reflection
of light
Ans: (b) Refraction
of light
Q: The size of the pupil of the eye is adjusted by:
(a) Cornea (b)
Optic nerve (c) Iris (d) Ciliary muscles
Ans: (c) Iris
Q: By what name is the physical quality columb/second
called?
(a) Volt
(b) Ohm (c) Ampere (d) Joule
Ans: (c) Ampere
Q: Which of the following is not attracted by a magnet?
(a) Steel (b) Cobalt (c) Brass (d) Nickel
Ans: (c) Brass
Q: The magnetic field inside a long straight solenoid
carrying current
(a) Is zero (b) Increases as we move towards its end (c) Decreases as we move towards its end (d) Is the same at all points.
Ans: (d) Is the same at all points.
Q: How many isomers of C₄H₁0 is possible?
(a) 2 (b) 3 (c) 4 (d) 5
Ans: (a) 2
Q: Which of the following is an ore of mercury metal?
(a) Rock salt (b) Calamine (c) Haematite (d) Cinnabar
Ans: (d) Cinnabar
Q: Burning of coal in air C + O2 → CO2 + Heat is a/an
(a) Endothermic reaction (b) Combination and Exothermic reaction (c) Displacement reaction
(d) None of these
Ans: (b) Combination
and Exothermic reaction
Q: The formula of baking soda is
(a) К2СО3 (b) KHCO3 (c) Na₂CO3
(d) NaHCO3
Ans: (d) NaHCO3
Q: A solution turns blue litmus red. Its pH is likely to
be:
(a) 7 (b) 5 (c)
8 (d) 14
Ans: (b) 5
Q: Which of the following cannot be considered receptor?
(a) Ear (b) Nose
(c) Muscle (d)
Eye
Ans: (c) Muscle
Q: Which of the following reproduces by forming spores?
(a) Fern (b) Planaria
(c) Spirogyra
(d) Potato
Ans: (a) Fern
Q: A gene is a
(a) Hybrid
(b) Heritable trait
(c) Pure breed (d)
Part of chromosome that transmits a trait
Ans: (d) Part of chromosome that transmits a trait
Q: The flow of energy is an ecosystem is always
(a) Unidirectional
(b) Bidirectional (c) Cyclic
(d) Multidirectional
Ans: (a)
Unidirectional
Q: One of the following is not a biodegradable material
this one
(a) Cotton (b) Animal bones (c)
Aluminium foil (d) Wood
Ans: (c) Aluminium foil
Note: For Next three questions, two statements are given (Assertion A and
reason R). Select the correct answer from the codes (a), (b), (c) and (d) as
given below
Code (a) A and R are true and R is correct explanation of A
Code (b) Both A and R are true and R is not correct
explanation of A
Code (c) A is true but R is false
Code (d) A is false but R is true
Q: Assertion (A) The height of an object is always
considered positive
Reasons (R) An object is always placed above the
principle axis in upward direction.
Ans: A and R are true and R is correct explanation of A
Q: Assertion (A) Pungent gas is produced when sulphur
burns in air
Reason (R) Sulphur trioxide is formed on reaction of
sulphur with oxygen
Ans: A is true but R
is false
Q: Assertion (A) The large intestine is the largest part
of alimentary canal.
Reason (R) Tiger has a shorter small intestine than
herbivores.
Ans: A is false but R is true
SECTION-B
(2 Marks each)
Q: A lens has a focal length of 150 mm what kind of lens
is it and what is its power?
Ans: Given, F = +150 mm i.e, + 0.15 m
We know,
Convex lens has positive focal length, hence it is CONVEX
lens.
P = 1/F
P = 1/0.15
P = + 6.66 D
Q: What is a balanced chemical equation? Write the
balanced chemical reaction for
Calcium hydroxide + carbon
dioxide > calcium carbonate + water
Ans: A balanced equation is a chemical equation which has
equal number of atoms in reactants as well as products.
Ca(OH)₂ + CO₂
→ CaCO₃ + H₂O
Q: What is the name of tissues which transport
(a) Food in a plant. (b)
Water and minerals in a plant.
Ans: (a) Food : Phloem (b)
Water and Minerals: Xylem
Q. A heating coil has a resistance of 200 Ohm. At what
rate will heat be produced in it when a current of 2.5 A flows through it?
Ans: Given, R
= 200 ohm, I = 2.5 A, P = ?
We Know,
P = I^2 R
P = (2.5)^2 x 200
P = 6.25 x 200
P = 1250 Watt
Q. Distinguish between the terms 'overloading and short
circuiting as used in domestic circuits.
Ans:
|
Overloading |
Short Circuit |
|
It occurs
when more than permitted current flows in circuit |
It occurs
when live wire comes in contact with neutral wire |
|
Resistance
doesn’t change |
Resistance
becomes almost zero |
Q. Give any two differences between soaps and detergents.
Ans:
|
Soaps |
Detergents |
|
Soaps are
sodium or Potassium salts of long chain fatty acids |
Detergents
are Ammonium or Sulphonate salts of long chain fatty acids |
|
Soaps don’t
work in hard water |
Detergents
work in hard water |
Q: Write equations of the chemical reactions involved
when water acts on: (a) Magnesium (b) Aluminium
Ans: (a) Magnesium: When Magnesium reacts with water, It
forms magnesium hydroxide and water
Mg + H2O Ã Mg(OH)2 + H2
(b) Aluminium: When Aluminium reacts with Water, It forms
Aluminium oxide and Hydrogen gas
Al + H2O
à Al2O3 + H2
Q. What is a plant hormone? Name four plant hormones.
Ans: Plant hormones are chemical substances produced in
plants which help in control and coordination in plants.
The four Plant Hormones are Auxins, Gibberellins, Cytokinins
and Abscisic acid
Q. Draw a neat labelled diagram of a flower showing its
various parts.
Ans: The flower is
reproductive part of plant. It has following parts:
Ans: Genetic variation may be defined as the difference in
DNA among a species. The variations occur due to mutation and
recombination.
All the human traits show variation such as height, Skin
colour, Blood group etc.
SECTION-C (3 Marks
each)
Q. What is dispersion of light? Mark the various colours
of spectrum by drawing diagram of dispersion through prism.
Ans: Dispersion means
the split of white light into seven colours.
When the rays of light enter Prism, it splits into spectrum of seven
colours called VIBGYOR i.e, Violet, Indigo, Blue, Green, Yellow, Orange, Red.
The light splits because different colours bend at different angles inside
prism.
The red light bends least and Violet bends most
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Q: What is Long sightedness? State its causes?
Ans: Long sightedness means Hypermetropia. A person
sees far off objects clearly but cant see nearby objects.
In hypermetropia, the rays of light meet behind Retina.
It is treated by convex lens.
Q: State Ohm's law. Define unit of resistance. What
happens to resistance as the conductor in made thinner?
Ans: Ohms law states that Current flowing in conductor is
directly proportional to Potential difference across its ends.
I.e ,
V ∝
I
V = I ×
R
Unit of Resistance: Ohm
When the conductor is made thinner, the resistance of the
conductor increases.
Q: Calculate the equivalent resistance when three
resistors of resistances 2 Ohm, 3 Ohm and 5 Ohm are connected in parallel.
Ans: Given R1 = 2, R2 = 3, R3= 5
We Know,
1/R = 1/R1 + 1/R2 + 1/R3
1/R = 1/2 +1/3 + 1/5
1/R = 15 + 10 + 6/30
1/R = 31/30
R = 30/31
R = 0.96 Ohm
Q: Define magnetic field. Draw a diagram to show the
magnetic field lines in a bar magnet.
Ans: Magnetic field is the space around a magnetic material
where it exerts its magnetic force.
The magnetic field lines around a bar magnet are given below;
Q: State Fleming's left hand rule. State two ways to increase the force on a current carrying conductor in a magnetic field.
Ans: Flemings left hand rule states that if we stretch the
thumb, fore finger and middle finger of our left hand in such a way that they
are mutually perpendicular to each other like X, Y and Z axis of a graph.
The forefinger represents points towards magnetic field, the middle finger
points towards direction of current, then thumb points towards direction of
motion of the conductor.
Q: What is meant by displacement reaction and double
displacement reaction? Explain with one example each?
Ans: The reaction in which one element takes place of
another in a compound is called displacement reaction. Example of displacement
reaction:
CuSO4
+ Zn ----------> ZnSO4
+ Cu
The reaction in which two compounds react by exchange of
ions to form new compounds is called double displacement reaction. Example of
Double displacement reaction:
AgNO3 + NaCl ------->
AgCl + NaNO3
Q: Explain the term rancidity What type of chemical
reaction is responsible for causing rancidity? How rancidity of food is
prevented?
Ans: Rancidity is a process in which foods made of oils and
fats get oxidized. This is characterized by bad smell and taste. Rancidity
occurs due to Oxidation.
The food containing fats and oils are flushed with unreactive nitrogen gas, so
there is no availability of oxygen to cause oxidation.
Q: Write down three properties of lonic compounds.
Ans: A. Ionic compounds contain Ions, Cations and Anions.
B. They are crystalline solids.
C. They have high Melting point and boiling points.
D. They are hard but brittle.
Q: Write a short note on Enrichment of ores.
Ans: Enrichment of Ore means removal of impurities like
sand, clay, rocky material and increasing quantity of ore. Following methods
are used:
1. Hydraulic washing: It separates ore from
impurities on basis of density. The lighter impurities wash away and ore, which
is heavy, settles down.
2. Froth Floatation: When ore is lighter than its
impurities, the ore is mixed with small quantities of oil and air is blown
in the tank. This leads to the formation of froth. The heavy impurities settle
down and are removed.
3. Magnetic separation
4. Leaching etc.
Q: What is plaster of paris? Write its chemical formula
and state two importance uses of it?
Ans: Plaster of paris is Calcium sulphate. Its formula is CaSO4.
1/2 H2O.
Uses:
It is used to make statues, models etc
It is used to treat fractures in bones.
It is used as fire proof material.
Q: What is meant by reactivity series of metals? Hydrogen
is not a metal but still it has been assigned a place in the reactivity series
of metals Why?
Ans: Reactivity series is the list of metals arranged in
decreasing order of their reaction with other elements and salts.
Hydrogen has been placed in the reactivity series as it also
forms H+ ions when displaced from its salts.
Q: What is corrosion? Name four methods of preventing
rusting of iron.
Ans: Corrosion is a natural process that occurs when a metal
deteriorates due to chemical reactions with air and moisture.
The various methods to prevent rusting of iron are: Painting,
Oiling, Greasing, Galvanizing, Chrome Plating etc.
Q: Write the names of regions in hind brain and give one
function of each region.
Ans: The Hind brain consists of three parts:
Pons varolli: It regulates breathing
Cerebellum: It maintains posture and equilibrium
of body.
Medulla Oblongata: It acts as reflex and respiratory
centre.
Q: What is a reflex action? Explain with the help of an
example.
Ans: Reflex action is set of quick, automatic and
spontaneous responses against stimuli. The reflex action occurs by reflex
arc.
Example withdrawing of hand upon touching hot object.
Q: What is the difference between two asexual methods of
reproduction fission and fragmentation?
Ans:
|
Fission |
Fragmentation |
|
The parent
cell divides into two or more daughter cells |
The parent
organism breaks into fragments |
|
It occurs in
Unicellular organisms |
It occurs in
multicellular organisms |
|
e.g Bacteria,
Protozoa |
e.g Algae |
Q: What is meant by Regeneration? Name two animals which
can regenerate fully from their cut body parts.
Ans: Regeneration means the regrowth of body part or
development of full organism from the fragment of its body. E.g Planaria, Hydra
etc
Q. Give two differences between food chain and food web.
Write down a food chain in the sea.
Ans:
|
Food Chain |
Food Web |
|
It is
sequence of Interlinked organisms who eat each other |
It is
interconnected network of many food chains |
|
Each step
represents a trophic level |
It provides
alternate pathways |
Food Chain at Sea:
Plankton Ã
Small Fish Ã
Large Fish Ã
Seal
Q: What is ozone? How is it formed? How it protects us
from harmful effects in the environment?
Ans: Ozone is a molecule of oxygen (O3). It forms a layer in
stratosphere and blocks Ultraviolet rays of sun from reaching earth.
The Ultraviolet rays will kill living organisms by causing
mutations. These rays can cause skin cancer, cataracts, and will destroy
ecosystems.
So Ozone is vital for all ecosystems on Earth because it
protects the environment from the harmful effects of UV radiation.
SECTION D (5
Marks Each)
Q: With the help of ray diagram, show the formation of
images when object is placed in front of a concave mirror (i) Between its pole
and focus (ii) Between its center of curvature and focus. Describe the nature,
size and position of the image formed in each case.
Ans: Object between Focus and Pole: The
image is formed behind the mirror. The image Virtual and erect.
Object between Centre of Curvature (C) and Focus (F): The
Image is formed beyond centre of curvature (C). The image is large, Real and
Inverted
Q: (a) State and explain the laws of refraction with the
help of a labelled diagram.
Ans: When light
enters from one medium to another, It bends towards the normal or away from it.
This process is called refraction.
1. The Incident Ray, Refracted Ray and z normal are all in same plane.
2. The ratio of Sin of angle of incidence to Sin of angle of refraction is
always constant. This is also called snells law.
(b) What is meant by refractive index?
Ans: Refractive Index is defined as Ratio of speed of
light in Vacuum to the speed of light in a medium.
Refractive index measures the change in direction of light ray when it changes
the medium
It is denoted by ų. It has no units.
Refractive index is given by=
Speed of light in Vaccum (C)/
Speed of
light in medium (V)
When light travels from one medium to another, It is
relative refractive index.
Q: (a) What is a
homologous series? Explain with an example.
Ans: Homologus series is a series of compounds that
has same structural formula, Properties and functional group. The homologus
series differ only in number of carbon atoms.
E.g, Homologus series of Aldehydes include
H -
CHO Methanal
CH3-
CHO Ethanal
C2H5 -
CHO Propanal
(b) State two characteristics of a homologous series.
Ans: Compounds of a
series only differ in carbon unit
2. They have a general formula.
3. They have same functional group.
4. They have similar chemical properties.
(c) The molecular formula of an organic compound is C18H36.
Name its homologous series.
Ans: Since the general formula of the compound is CnH2n,
Therefore it belongs to Alkenes.
Q: (a) What are hydrocarbons? Explain with examples.
Ans: Hydrocarbons are the Compounds that of Carbon and
Hydrogen in a fixed proportion. They include Alkanes, Alkenes & Alkynes.
(b) Explain the meaning of saturated and unsaturated
hydrocarbons with two examples each.
|
Saturated Hydrocarbons |
Unsaturated Hydrocarbons |
|
They have single covalent bond |
They have double or triple covalent bond |
|
The general formula is CnH2n+2 |
The general formula is CnH2n or CnH2n-2 |
|
They are less reactive |
They are more reactive |
|
They include Alkanes |
They include Alkenes and Alkynes |
|
They burn with clean flame |
They burn with sooty flame |
Q: Draw a labelled diagram of human excretory system.
Ans: Excretion means elimination of metabolic wastes, salts
and extra water from body.
These wastes may lead to death of cells in body.
Excretory system of humans:
The excretory system of humans consist of:
1. Pair of Kidneys 2. Ureters 3. Urinary bladder 4. Urethra
Q: What is the function of excretory system in humans?
Ans: The
excretory system has many functions which include:
I. It
helps get rid of nitrogenous waste
II. It
helps get rid of extra water
III. It
helps get rid of excess salts
Q: What are herbivores, carnivores and omnivores? Give
two examples of each.
Ans: Herbivores: Herbovores are the animals that eat only
plant and plant based products e.g Cow, Deer, Horse etc.
Carnivores: Carnivores are the animals that specifically eat
other animals for food. E.g. Lion, Tiger etc.
Omnivores: Omnivores are the animals that eat both
plant-based or animal based diets. E.g. Man, Bear etc.
Q: Name the five steps which occurs in the process of
nutrition in animals?
Ans: The five steps involved in the process of Nutrition
are:
I. Ingestion II. Digestion III. Absorption IV. Assimilation V. Egestion
