# mcq questions for class 10 science pdf download | science class 10 mcq

Q. 1 ) The focal length of the convex lens is:

(a) + 10 cm (b) + 20 cm
(c) – 10 cm (d) – 20 cm

From S.No. 3, we can say that the radius of
curvature of the lens is 20 cm because when
an object is placed at the centre of curvature of
a convex lens its image is formed on the other
side of the lens at the same distance from
the lens. And, we also know that focal length
is half of the radius of curvature. Thus, focal
length of the lens is + 10 cm.

Q. 2) The separation of the left and right side of the heart is useful in:

(a) Preventing oxygenated and deoxygenated blood from mixing

(b) Pumping blood to different body parts  efficiently

(c) Exchange of gases

(d) Ensuring that blood flows in one direction  only

Answer: (a) Preventing oxygenated and deoxygenated blood from mixing

Explanation: The separation of the left and
right side of the heart is useful in preventing
oxygenated and deoxygenated blood from
mixing which ensures an efficient supply of
oxygen to the body

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Q. 3) The blood vessel that collects the blood from different organs and brings it back to the heart is:

(a) Arteries (b) Veins
(c) Capillaries (d) Lymph

Explanation: Veins collect the blood from
different organs and brings it back to the
heart. They do not need thick walls because
the blood is no longer under pressure.

Q. 4) The colour of the scattered light depends on:

(a) Size of the scatterer
(b) Total internal reflection
(c) Dispersion of light
(d) Atmospheric refraction

Answer: (a) Size of the scatterer

Explanation: The colour of the scattered light
depends on the size of the scattering particles.
very fine particles scatter mainly blue light
whereas larger sized particles scatter light of
longer wavelengths.

Q. 5) The apparent flattening of the sun’s disc at sunrise and sunset is due to:

(a) Dispersion of light
(b) Atmospheric refraction
(c) Scattering of light
(d) Diffraction of light

Explanation: Due to atmospheric refraction,
the sun’s rays bend continuously towards the
normal before it reaches the earth’ surface
as it travels from a rarer medium to a denser
medium.

Q. 6) Which of the following are ionic compounds?

(I) MgCl2

(II) HCl

(III) CCl4

(IV)Na2O

(a) Both (I) and (II)

(b) Both (II) and (III)

(c) Both (I) and (IV)

(d) (I), (II) and (IV)

Explanation: Ionic compounds are formed
between metals and non-metals by the transfer
of electrons from the metal atom to the atom
of non-metal. In the given question, Mg and Na
are metals and Cl and O are non-metals and
therefore will form ionic compounds.

Q. 7) Which is the most reactive metal?

(a) P (b) Q
(c) R (d) S

Explanation: According to reactivity series,
Zn > Fe > Cu > Ag
Since, Zn is the most reactive, but no metal
showed reaction with ZnSO4. After zinc, iron
is more reactive and only metal Q showed
displacement reaction. Thus, it is the most
reactive.

Q. 8) Which is the least reactive metal?

(a) P (b) R
(c) Q (d) S

Explanation: Metal S is least reactive as it
could not show any displacement reaction
with any of the given solutions.

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Q. 9) What would you observe if Q is added to a solution of copper (II) sulphate?

(a) Combination reaction takes place
(b) Decomposition reaction takes place
(c) Displacement reaction takes place
(d) No reaction takes place

Answer: (c) Displacement reaction takes place.

Explanation: Since Q is most reactive and
displaced iron from iron sulphate, it displace
copper from copper sulphate as well.

Q. 10) The increasing order of reactivity of metals P, Q, R and S is :

(a) P < Q < R < S (b) S < R < Q < P
(c) S < R < P < Q (d) Q < P < R < S

Answer: (c) S < R < P < Q

Explanation: Q is the most reactive and S is
the least reactive metal. As metal P displace
Cu from CuSO4, but R does not. So, P is more
reactive than R.

Q. 11) A network of tiny blood vessels located at the beginning of a nephron is:

(a) Renal calyces
(b) Renal pyramid
(c) Glomerulus
(d) Bowman’s capsule

Explanation: The glomerulus (plural glomeruli), is a network of small blood vessels (capillaries) known as a tuft, located at the beginning of a nephron in the kidney.

Q. 12) Each kidney is made up of a large number of excretory units called:

(a) Glomerulus
(b) Nephrons
(c) Bowman’s Capsule
(d) Blood capillaries

Explanation: Nephrons are the filtration units
present in the kidneys which are packed close
together. Every human has two kidneys. The blood arrives at the kidney via the renal artery, which splits into many afferent arterioles. These arterioles go to the Bowman’s Capsules of nephrons, where the wastes are taken out of the blood by pressure filtration. The renal pelvis takes urine away from the kidney via the ureter. Both of the ureters lead the urine into the body’s only urinary bladder, which expands and sends nerve impulses when full. From there, urine is expelled through the urethra and out of the body.

Q. 13) The correct sequence of urine formation is

(a) Filtration, reabsorption, secretion
(b) Secretion, reabsorption, filtration
(c) Reabsorption, secretion, filtration
(d) Reabsorption, filtration secretion

Explanation: Filtration involves the transfer
of soluble components, such as water and
waste, from the blood into the glomerulus.
Reabsorption involves the absorption of
molecules, ions, and water that are necessary
for the body to maintain homeostasis from the
glomerular filtrate back into the blood.
Secretion involves the transfer of hydrogen
ions, creatinine, drugs, and urea from the blood into the collecting duct, and is primarily made of water. Blood and glucose are not normally found in urine.

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Q. 14) The speed of light in air 300000 km/s
whereas that of speed in a glass slab is
about 197000 km/s. What is the reason
for the difference in speed of light in two
media?

(a) Difference in density.
(b) Difference in amount of light.
(c) Difference in density of wind flow.
(d) Difference in temperature.

Explanation: The speed of light varies with
density as the medium with higher density
decreases the speed of light and medium with
lower density increases the speed of light.

Q. 15) Which of the following explains the law of refraction of light through the glass slab?

(a) Light always bends towards the normal in a glass slab.

(b) The incident ray, the refracted ray, and the normal to the interface always lie on the same plane.

(c) Ray of light travelling in the air is always considered as the incident ray, and the one in the glass is the refracted ray.

(d) Ray of light always travels in a straight path irrespective of change in medium.

Answer: (b) The incident ray, the refracted ray, an the normal to the interface always lie on the same plane.

Explanation: All the refracted rays follows the
first law of refraction i.e., the incident ray, the

Q. 16) The speed of light in air is 3 × 108 ms–1, whereas that of the speed of light in water is 2.26 × 108 ms–1. What is the refractive index of water with respect to air?

(a) 2.64 (b) 1
(c) 1.32 (d) 0.75

Q. 17) A ray of light continues moving along the same path while passing through air, glass interface. The angle of incidence for the ray is:

(a) zero (b) 90º
(c) less than 90º (d) grater than 90º

Explanation: No, bending of light occurs when
light is incident normally on a boundary two
media, since angle of incidence and angle of
refraction, both are zero.

Q. 18) When a lead salt X is heated in a test tube, brown fumes of a gas Y are emitted, along with lead oxide and oxygen gas.

Identify the lead salt X and brown gas Y
and select the row containing the correct
substances and the type of reaction involved:

Answer: (b) X → Lead Nitrate, Y → Nitrogen dioxide Reaction type → Decomposition Reaction

Explanation: When lead nitrate is heated, it
undergoes decomposition reaction to form

Q. 19) Which salt has pH more than 7 in solution form:

(a) Na2CO3 (c) NaCl
(b) CaCO3 (d) CaCl2

Explanation: Sodium carbonate (Na2CO3)
solution has pH more than 7 as on dissolving
in water, it gives weak acid, H2CO3 and strong
base, NaOH.

Q. 20) Arrange the metals Ca, Al, Mg and Zn in decreasing order of their reactivities:

(a) Mg > Ca > Al > Zn
(b) Ca > Mg > Al > Zn
(c) Mg > Ca > Zn > Al
(d) Ca > Mg > Zn > Al

Answer: (b) Ca > Mg > Al > Zn

Explanation: Metals have been arranged
based on their relative reactivities in a series

Q. 21) HCl is a stronger acid than acetic acid
because:

(a) HCl turns litmus solution red.

(b) HCl is corrosive in nature, but acetic acid not.

(c) HCl dissociates completely, but acetic acid do not.

(d) HCl and acetic acid are equally stronger.

Answer: (c) HCl dissociates completely, but acetic acid do not.

Explanation: HCl is stronger acid than acetic
acid because it ionises completely in aqueous
solution while acetic acid is only partially
ionised in aqueous solution.

Q. 22) Respiration is considered as an exothermic process because.

(I) During respiration, digested food is
broken down and ATP is released.

(II) During respiration, body temperature is  increased.

Select the correct option.

(a) Statement (I) is correct

(b) Statement (II) is correct

(c) Both (I) and (II) are correct

(d) Both (I) and (II) are incorrect

Explanation: The respiration included breaking down of digested food using oxygen. Since the respiration process produces a lot of energy in form of ATP, it is exothermic process in nature.

Q. 23) An aqueous solution ‘A‘ turns phenolphthalein solution pink. On addition of an aqueous solution ‘B‘ to ‘A‘, the pink colour disappears. The following statement is true for solution ‘A‘ and ‘B‘.

(a) A is strongly basic and B is a weak base.

(b) A is strongly acidic and B is a weak acid.

(c) A has pH greater than 7 and B has pH  less than 7.

(d) A has pH less than 7 and B has pH
greater than 7.

Answer: (c) A has pH greater than 7 and B has pH less than 7.

Explanation: Acids have pH less than 7 and
alkalis have pH more than 7.
(1) Phenolphthalein is an organic dye and in
neutral or acidic solution, it is colourless
while in the basic solution, the colour of
phenolphthalein changes to pink. So the
aqueous solution
‘A‘ which turns phenolphthalein pink is
basic or alkaline and has pH greater than
7.
(2) On addition of an aqueous solution of ‘B‘
to ‘A‘, the pink colour disappears, it means
neutralisation reaction has taken place.
Hence, aqueous solution of B is acidic in
nature and has pH less than 7

Q. 24) The increase in pH value from 7 to 14
indicates:

(a) Increase in concentration of OH–
ions

(b) Increase in concentration of H+ ions

(c) Decrease in concentration of OH–
ions

(d) No change in concentration of OH–
ions

Answer: (a) Increase in concentration of OH–
ions

Explanation: Increase in the value of pH from
7 to 14 indicates that the alkaline nature is
increasing due to increase in concentration of
hydroxyl or OH– ions.

Q. 25) What is the difference between the following two types of reactions ?

(I) AgNO3 + HCl → AgCl + HNO3

(II) Mg + 2HCl → MgCl2 + H2

(a) Reaction I is double displacement
reaction.

Reaction II is single displacement
reaction.

Answer: (a) Reaction I is double displacement reaction Reaction II is single displacement reaction

Explanation: The first reaction is a double
displacement reaction whereas second
reaction is a single displacement reaction

Q. 26) The graph below shows the variation of rate of photosynthesis with light intensity for different levels of carbon dioxide.

After analyzing the graph a student writes the following statements.

(I) The rate of photosynthesis increases linearly with light intensity.

(II) The rate of photosynthesis first increases linearly with increase in light intensity and then becomes constant.

(III) For a given light intensity, the rate of photosynthesis will be more if carbon dioxide concentration is less.

(IV)For a given light intensity, the rate of photosynthesis does not depend upon the carbon dioxide
concentration. Choose from the following which of the following would be the correct statement(s).

(a) Only I (b) Only II
(c) Both I and III (d) Both II and IV

Explanation: The rate of photosynthesis first
increases linearly with increase in light intensity and then becomes aconstant. Moreover, it also depends upon the carbon dioxide concentration in the atmosphere. More the concentration of carbon dioxide, faster will be the rate of photosynthesis for a given intensity of light.

Q. 27) What protects the inner lining of stomach from hydrochloric acid?

(a) Muscle
(b) Mucus
(c) Basement membrane
(d) Alkaline solution

Explanation: The inner lining of stomach is
protected from hydrochloric acid by mucus.

Q. 28) What will happen to a plant if its xylem is removed?

(a) No conduction of water and minerals
(b) No conduction of organic material
(c) Death of plant would occur
(d) Both (a) and (c)

Answer: (d) Both (a) and (c)

Explanation: The xylem tissue transports
water and minerals from the soil to the
leaves of a plant for photosynthesis. If xylem
is removed, upward movement of water will stop leading to wilting of leaves and ultimately causes death of a plant.

Q. 29) What are the end products of anaerobic
respiration in yeast?

(a) CO2 and water
(b) Alcohol and CO2
(c) Alcohol and Water
(d) Oxygen and Water

Explanation: The end product is obtained by
anaerobic respiration of yeast are ethyl alcohol
and carbon dioxide

Q. 30) A student performed an activity to
understand the role of saliva in digestion. He
took two test tubes labelled I and II having
starch solution and starch solution with
saliva respectively. He then added few drops
of iodine to the test tubes

Select the row containing correct observation from the table below :

Answer: (a) Test tube I → No change in colour
Test tube II → Colour changes to blue black

Explanation: We will observe a colour change
in test tube B, showing presence of starch.
Where as test tube A will show no colour
change as due to addition of saliva, starch is
converted into sugar by the enzyme salivary
amylase