TRIFOCUS CLASSES
X CBSE SCIENCE PRELIMS
Class 10 - Science
Time Allowed: 3 hours
Maximum Marks: 80
Section A
1.
Which of the following are exothermic processes?
[1]
i. Reaction of water with quick lime
ii. Dilution of an acid
iii. Evaporation of water
iv. Sublimation of camphor (crystals)
2.
a) (i) and (ii)
b) (iii) and (iv)
c) (ii) and (iii)
d) (i) and (iv)
Four student used the following four combinations of reactants to observe the properties of HCl and NaOH.They [1]
would observe a black residue in the test tubes :
I. Zn and dil. NaOH solution
II. Zn and dil. HCl solution
III. Na2CO3 and dil. NaOH solution
IV. Na2CO3 and dil. HCl solution
There would be a rapid evolution of a gas in cases stated by response
3.
4.
5.
a) I and II
b) II and IV
c) I and IV
d) I and III
What happens when ammonia reacts with hydrogen chloride? NH3 + HCl → ?
a) Both H2 and NH4Cl
b) H2 gas is evolved
c) NH4Cl is formed
d) Cl2 gas is evolved.
Which of the following gas is used in welding and cutting metals?
a) All of these
b) Ethyne
c) Ethane
d) Ethene
[1]
[1]
In order to complete the diagram of stomatal apparatus given below, nuclei should be drawn in the parts marked. [1]
a) A, B and C
b) B and C
c) A and C
d) A and B
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6.
Match the following with correct response.
[1]
Column A
7.
Column B
(i) The master gland
(a) Control cell division and cell growth
(ii) Cytokinin
(b) Regulates metabolism
(iii) Insulin
(c) Reduces blood sugar
(iv) Thyroxine
(d) Pituitary gland
a) (i) - (d), (ii) - (a), (iii) - (c), (iv) - (b)
b) (i) - (c), (ii) - (b), (iii) - (d), (iv) - (a)
c) (i) - (b), (ii) - (d), (iii) - (a), (iv) - (c)
d) (i) - (a), (ii) - (c), (iii) - (b), (iv) - (d)
Select the statements that describe characteristics of genes
[1]
i. genes are specific sequence of bases in a DNA molecule
ii. a gene does not code for proteins
iii. in individuals of a given species, a specific gene is located on a particular chromosome
iv. each chromosome has only one gene
8.
9.
a) (ii) and (iv)
b) (i) and (ii)
c) (i) and (iii)
d) (i) and (iv)
Which of the following ray diagrams is correct for the ray of light incident on a lens shown in Fig.?
a)
b)
c)
d)
At noon the sun appears white as
a) light is least scattered
[1]
[1]
b) all the colours of the white light are
scattered away
c) red colour is scattered the most
10.
11.
d) blue colour is scattered the most
The resistivity does not change if
[1]
a) the shape of the resistor is changed
b) the temperature is changed
c) both material and temperature are changed
d) the material is changed
Assertion (A): Baking soda creates acidity in the stomach.
[1]
Reason (R): Baking soda is alkaline.
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a) Both A and R are true and R is the correct
b) Both A and R are true but R is not the
explanation of A.
c) A is true but R is false.
12.
correct explanation of A.
d) A is false but R is true.
Assertion (A): Units that make up the nervous system are called neurons.
[1]
Reason (R): Nerve impulses are carried by dendrites towards the cell body.
a) Both A and R are true and R is the correct
b) Both A and R are true but R is not the
explanation of A.
c) A is true but R is false.
13.
correct explanation of A.
d) A is false but R is true.
Assertion (A): The 200 W bulbs glow with more brightness than 100 W bulbs.
[1]
Reason (R): A 100 W bulb has more resistance than 200 W bulb.
a) Both A and R are true and R is the correct
b) Both A and R are true but R is not the
explanation of A.
c) A is true but R is false.
14.
correct explanation of A.
d) A is false but R is true.
Assertion (A): Man is an omnivore.
[1]
Reason (R): Man eats food products obtained from both plants and animals.
a) Both A and R are true and R is the correct
b) Both A and R are true but R is not the
explanation of A.
c) A is true but R is false.
correct explanation of A.
d) A is false but R is true.
15.
Which gas is evolved when sodium hydrogen carbonate (NaHCO3) is added to acetic acid?
[1]
16.
What is the source of oxygen liberated in photosynthesis?
[1]
17.
What is an optically rarer medium?
[1]
18.
Nichrome is used to make the element of electric heater. Why?
[1]
Section B
19.
Rohit wants to have an erect image of an object using a converging mirror of focal length 40 cm.
[2]
i. Specify the range of distance where the object can be placed in front of the mirror. Give reason for your
answer.
ii. Will the image be bigger or smaller than the object?
iii. Draw a ray diagram to show the image formation in this case.
20.
B1, B2 and B3 are three identical bulbs connected as shown in figure. When all the three bulbs glow, a current of [2]
3A is recorded by the ammeter A.
What happens to the reading of A1, A2, A3 and A when the bulb B2 gets fused?
21.
Why does a current carrying conductor kept in a magnetic field experience force? What is the direction of force
[2]
acting on the conductor?
22.
Explain, how pesticides get accumulated in the environment.
[2]
Section C
23.
If a plant is releasing carbon dioxide and taking in oxygen during the day, does it mean that there is no
[3]
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photosynthesis occurring? Justify your Answer.
24.
In Mendel's experiment of inheritance in which he took two contrasting characters, i.e. round green and wrinkled [3]
yellow seeds,
i. What was the phenotype of offsprings in F1 - generation?
ii. What was the ratio of offsprings in F2 - generation?
25.
A household uses the following electric appliances:
[3]
i. The refrigerator of rating 400 W for 10 h each day and Two electric fans of rating 80 W each for 6 h daily.
ii. Six electric tubes of rating 18 W each for 6 h daily.
Calculate the electricity bill for the household for the month of June, if the cost of electrical energy is Rs 3
per unit.
26.
A circular metallic loop is kept above the wire AB as shown below:
[3]
What is the direction of induced current produced in the loop, if the current flowing in the straight wire
i. is steady, i.e. does not vary?
ii. is increasing in magnitude?
Section D
Question No. 27 to 31 are based on the given text. Read the text carefully and answer the questions:
4.0
When a more reactive element displaces a less reactive element from its compound, it is called a displacement reaction.
The reaction is of two types. Single displacement reaction and double displacement reaction.
Iron being more reactive than copper displaces copper from an aqueous solution of copper sulphate. This is an example
of a single displacement reaction.
On adding silver nitrate solution to sodium bromide, a yellow ppt of silver bromide and solution of sodium nitrate is
formed. This is an example of a double displacement reaction.
27. When dil. sulphuric acid is added to pieces of iron sulphide, hydrogen sulphide gas is produced and soluble ferrous
sulphate is formed. Which chemical reaction is involved in this process?
28. Mention reaction which is used for the preparation of oxygen gas in the laboratory.
29. What are the products formed in the double displacement reaction discussed below?
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30. Which elements displace aluminum from its salt?
31. Mention one double displacement reaction?
32.
Read the following and answer the questions any four from (i) to (v):
[4]
Light gets refracted through the transparent prism. Issac Newton uses a glass prism to obtain the spectrum of
sunlight. He tried to spit the colours of the spectrum of white light.
i. Which of the following statements is correct regarding the propagation of light of different colours of white
light in air?
a. Red light moves fastest.
b. Blue light moves faster than green light.
c. All the colours of the white light move at the same speed.
d. Yellow light moves with the mean speed as that of the red and the violet light
ii. In the above diagram the angle of incidence, the angle of emergence and the angle of deviation respectively
are (select the correct option):
a. X, R and T
b. Y, Q and T
c. X, Q and P
d. Y, Q and P
iii. While performing the experiment to trace the path of a ray of light passing through a glass prism, four
students marked the incident ray and the emergent ray in their diagrams in the manner shown below.
The correct path of the rays has been shown by:
a. I
b. II
c. III
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d. IV
iv. A student traces the path of a ray through a glass prism for four different values of angle of incidence. On
analysing the diagrams he is likely to conclude that the emergent ray
a. is always parallel to the incident ray.
b. is always perpendicular to the incident ray.
c. is always parallel to the refracted ray.
d. always bends at an angle to the direction of the incident ray.
v. The splitting of light into its component colours is called
a. Spectrum
b. Dispersion
c. Tyndall effect
d. Refraction
33.
Read the following and answer any four questions:
[4]
Electric power is the rate of doing work or consumption of energy. Power is given by the rate at which electric
energy is dissipated or consumed in an electric circuit. It is also term as electric power. The commercial unit of
electric energy is kilo-watt-hours commonly known as a unit.
i. The S.I unit of electric power is
a. Volt
b. Joule
c. Watt
d. Coulomb
ii. An electric heater is rated at 2 KW electrical energy cost 4 per kWh. What is the cost of using the heater
a. ₹ 12
b. ₹ 24
c. ₹ 36
d. ₹ 48
iii. Power may be given by
a. P = VI
b. P =
I
c. P =
V
2
R
2
R
d. all of these
iv. 1 Kilowatt is equal to
a. 1000 watts
b. 100 watts
c. 10000 watts
d. 10 watts
v. An electric bulb is connected to a 220V generator. The current is 0.50 A, what is the power of the bulb?
a. 50W
b. 110W
c. 550W
d. 220W
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Section E
34.
Describe the mechanism of breathing in human being.
[5]
Or
Explain clearly how the air is inhaled and exhaled during breathing in humans.
35.
a. Why is the use of iodised salt advisable? Name the disease caused due to deficiency of iodine in our diet and
[5]
state its one symptom.
b. How do nerve impulses travel in the body? Explain.
36.
What are the rules to form image of an object by concave lens? Form the images of an object when it is moved
[5]
from infinity to the lens.
37.
Obtain an expression for the heat produced in a conductor when a voltage V is applied across it. Heating effect
[5]
of electric current is desirable as well as undesirable. Explain this statement.
38.
Draw an appropriate schematic diagram showing common domestic circuits and discuss the importance of fuse.
[5]
Why is it that a burnt out fuse should be replaced by another fuse of identical rating?
39.
Industrialization is one of the main cause of deterioration of environment. List any four reasons in favour of [5]
this statement.
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