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Half Yearly Examinations X Class Physical Sciences Paper - I Model
Paper (English Version)
Time: 2 Hours PART - A Marks: 35
SECTION – I
Note: 1) Answer any FIVE questions choosing atleast TWO from each group.
2) Each question carries TWO marks. 5 2 10
GROUP - A
1. What are the factors that influence the value of acceleration due to gravity on
earth?
2. Define time of flight. Find time of flight of a body when it is thrown up
vertically with a velocity 20 m/s. (Take g = 10 m/s2.)
3. Velocity of a sound wave in air is 360 m/s and in water is 1440 m/s. If the
wavelength of sound wave in air is 2 cm, then what is its wavelength in water?
4. What are the factors on which does speed (R.P.M.) of an electric motor depend?
GROUP - B
5. State the following laws:
(a) Dobereiner law of triad (b) Mendeleef's periodic law.
6. Write electrode reactions that take place during the extraction of Magnesium.
7. Define pH and calculate the pH of 0.0001 M HCl.
8. Mention names of any four fatty acids.
SECTION - II
Note: 1) Answer any FOUR questions among the following.
2) Each question carries ONE mark. 4 1 4
9. How are micro waves produced?
10. What is chemical effect of electricity?
11. Mention any two uses of radio isotopes in agriculture.
12. Explain why heat of neutralization is less than 13.7 K.cal/mole for a reaction
involving a weak acid or a weak base.
13. What is hydrogenation of oils?
14. Draw the structure of Benzene molecule.
SECTION - III
Note: 1) Answer any FOUR questions choosing at least TWO questions from
each group.
2) Each question carries FOUR marks. 4 4 16
GROUP – A
1 1 1 1 15. Derive .
R R1 R2 R3
16. Write differences between centripetal force and centrifugal force.
17. How do you find thickness of a glass plate by using a screw gauge?
18. What is magnetic moment? Calculate the value of magnetic induction at a
distance 0.5 m on the axial line of a short bar magnet of length 5 cm. and pole
strength 2 10�3 A-m.
GROUP - B
19. Define ionization energy and explain the factors that influence it.
20. Explain the formation of triple bond with an example.
21. Define molarity. 6 grams of urea is present in 200 ml of its aqueous solution.
Calculate the molarity of the solution. (Molecular weight of urea is 60.)
22. What are the differences between diamond and graphite.
SECTION - IV
Note: 1) Answer any ONE among the following.
2) This question carries FIVE marks. 1 5 5
23. Draw a neat diagram of Nuclear Reactor and label its parts.
24. Draw a neat diagram to show the manufacture of alcohol.
Time: 30 Minutes PART - B Marks: 15
I. Pick out the correct answer and fill in the brackets with capital letter of the
correct answer chosen. 10 1
5 2
1. Acceleration due to gravity on the surface of the earth is 9.8 m/s2. Acceleration
due to gravity at a height of 6400 km from the surface of the earth is (Radius of
earth is 6400 km) ( )
A) 24.5 m/s2 B) 245 m/s2
C) 2.45 m/s2 D) 0.245 m/s2
2. A metallic disc is rotating about its axis passing through its centre with an angu-
lar speed ''. Its angular speed at a point in between centre of the disc and edge
of the disc is ( )
A) B) 2 C) �2 D) 2
3. The phase difference between two points of a wave separated by its wave length
is ( )
A) 2 Radians B) Radians
2
C) Radians D) Radians
4
4. Light source that emits coherrent light is ( )
A) Coolidge tube B) Mercury vapour lamp
C) Laser D) Bunsen burner
5. Magnetic moment of a barmagnet of pole strength 25 A-m is 5 A-m2.
The length of the magnet is ( )
A) 10 cm B) 30 cm C) 5 cm D) 20 cm
6. The quantum number that decides the shape of an orbital is ( )
A) Principal B) Azimuthal
C) Magnetic D) Spin
7. The number of elements present in 4th period of a periodic table is ( )
A) 2 B) 8 C) 32 D) 18
8. Which is not an Arrhenius acid among the following? ( )
A) HCl B) CO2 C) HNO3 D) H2CO3
9. The number of peptide bonds present in tripeptide is ( )
A) 3 B) 2 C) 6 D) 4
10. The salt that is responsible for hardness of water among the following is ( )
A) CaCl2 B) NaCl C) KCl D) Na2CO3
II. Fill in the blanks. 10 1
5 2
11. If a ball is thrown up vertically with a velocity 19.6 m/s, then the maximum
height reached by it is ..........
12. ........ rays are emitted by molecules when they change their states of rotational
or vibrational motion.
13. If 200 waves cross a point in one second, then its time period is ......... sec.
14. Total solid angle at the centre of a sphere is ......... steridians.
15. 14
4 �
1 .........
N He H
7 2 1
16. The number of degenerating orbitals in a f-subshell is .........
17. Element with electron configuration [Ar] 3d24s2 belongs to ......... block of a
periodic table.
18. The number of water molecules Carnalite loses when it is heated is ..........
19. If the mole fraction of a solute of a solution is 0.3, then the mole fraction of the
solvent of the solution is ..........
20. The chemical formula of Aluminium Carbide is ........
III. Match the Following. 10 1
5 2
(i) GROUP - A GROUP - B
21. Centripetal force [ ] A. Same mass number
22. Magnetic susceptibility [ ] B. Same atomic number
23. Isotopes [ ] C. Luminous flux/ Solid angle
24. Isobars [ ] D. Solid angle/ Luminous flux
25. Intensity of light [ ] E. = I H
H
F. = I
mv2 G.
r
II. GROUP - A GROUP - B
26. Pentane [ ] A. C6H14
27. Acetic acid [ ] B. C4H8
28. Pentyne [ ] C. CH3COOH
29. Butene [ ] D. C5H12
30. Hexane [ ] E. C5H8
F. C2H5COOH
G. C6H12
ANSWERS SECTION - I
GROUP - A
1. What are the factors that influence the value of acceleration due to
gravity on earth?
Ans: The factors influencing acceleration due to gravity on earth:
★ The value of 'g' decreases with the increase of altitude.
★ The value of 'g' decreases with the increase of depth.
★ The value of 'g' is maximum at poles.
★ The value of 'g' is minimum at equator.
★ The value of 'g' changes slightly due to local conditions such as concrete
buildings, presence of minerals inside the earth etc.
2. Define time of flight. Find time of flight of a body when it is thrown up
vertically with a velocity 20 m/s. (Take g = 10 m/s2.)
Ans: Time of flight is the sum of the time of ascent and the time of descent of a body
which is thrown up vertically.
Initial velocity u = 20 m/s; g = 10 m/s2
2u 2 20 Time of flight = = = 4 seconds. g
10
3. Velocity of a sound wave in air is 360 m/s, and in water is 1440 m/s. If the
wavelength of sound wave in air is 2 cm, then what is its wavelength in
water?
Ans: Velocity of sound wave in air Va = 360 m/s = 36,000 cm/s Velocity of
sound wave in water Vw = 1440 m/s = 1,44,000 cm/s Wavelength of wave
in air a = 2 cm; wavelength of wave in water w = ?
Vw w We know that =
Va a
1,44,000 w =
36,000 2
1,44,000 2 w = = 8 cm.
36,000
4. What are the factors on which does speed (R.P.M.) of an electric motor
depend?
Ans: The speed (R.P.M.) of an electric motor depends on the following factors:
★ Number of turns of the armature (n)
★ Area of the armature (A)
★ Strength of the electric current (i)
★ Magnetic field Induction (B)
The speed (R.P.M.) can be increased by increasing n, A, i and B.
GROUP - B
5. State the following laws:
a) Dobereiner's law of triad b) Mendeleef's periodic law
Ans: 1. Dobereiner's law of triad: In the triads of elements, the atomic weight of the
middle element is found to approximately equal to the arithmetic mean of
the first and third elements or have nearly same atomic weights.
2. Mendeleef's periodic law: The properties of elements are the periodic
functions of their atomic weights.
6. Write electrode reactions that take place during the extraction of
Magnesium.
Ans: MgCl2 (molten) � Mg2+ + 2C �
.............(i)
l
Reaction at cathode: Mg2+ + 2 e � Mg ............. (ii)
Reaction at anode: 2Cl� � Cl2 + 2e .............(iii)
MgCl2 � Mg + Cl2 .............(iv)
7. Define pH and calculate the pH of 0.0001 M HCl.
Ans: pH is defined as the negative logarithm of H+ ion concentration.
[H+] = 0.0001 = 10�4; pH = �log10 [H+]
= �log10 [10�4] = 4 log10 [10] = 4.
8. Mention names of any four fatty acids.
Ans: Fatty acids are 1) Lauric acid 2) Stearic acid
3) Oleic acid 4) Linoleinic acid.
SECTION - II
9. How are microwaves produced?
Ans: Microwaves are commonly produced by electromagnetic oscillators with high
frequency (109 � 1011) Hertz in electric circuits.
10. What is chemical effect of electricity?
Ans: The process of decomposition of a chemical compound in a solution when an
electric current passes through it is called electrolysis or chemical effect of
electricity.
11. Mention any two uses of radio isotopes in agriculture.
Ans: Uses of radio isotopes in agriculture:
★ Unnecessary mutations of plants can be prevented by irradiating seeds using
radio isotopes.
★ Perishable cereals, onions, gram etc. are kept fresh beyond their normal life
by exposing them to mild - radiation.
12. Explain why heat of neutralization is less than 13.7 K.cal/mole for a
reaction involving a weak acid or a weak base.
Ans: The difference in the heat of neutralization is caused due to consumption of
some heat to ionize the weak acid or weak base.
13. What is hydrogenation of oils?
Ans: Converting oils into fats by passing Hydrogen gas into oils in presence of a
catalyst (Ni) is known as hydrogenation of oils.
Ni H2 + oil � fat
unsaturated saturated
14. Draw the structure of Benzene molecule.
Ans: Benzene
CH CH CH
HC CH HC CH HC CH
(or) (or)
HC CH
HC CH
HC CH
CH CH CH
SECTION - III
GROUP - A
1 1 1 1 15. Derive
R R1 R2 R3
Ans: R1
A i2 R2
B
i3 R3
i i
( ) A
K
★ Connect resistances R1, R2 and R3 in parallel as shown in figure.
★ Let the potential difference across AB be 'V' volts.
★ Let the current delivered by the cell be 'i' amperes.
★ Let the currents through resistances R1, R2 and R3 be i1, i2 and i3
respectively. So
i = i1 + i2 + i3 (1)
★ Applying Ohm's law to resistance R1 we get
V = i1R1 i1 = V
(2)
R1
★ Applying Ohm's law to resistance R2 we get
V = i2R2 i2 = V
(3)
R
2
★ Applying Ohm's law to resistance R3 we get
V = i3R3 i3 = V
(4)
R3
★ From (1), (2), (3) and (4) equations we get
] (5)
R1 R2 R3 R1 R2 R3
★ Let the resultant resistance of R1, R2 and R3 be R
★ Applying Ohm's law to resistance 'R' we get
V V = iR i = (6)
R
ww
★ From equations (5) and (6) we get
= V[ + + ]
V 1 1 1
R R1 R2 R3
1
= 1
+ 1
+ 1
R R1 R2 R3
16. Write differences between centripetal force and centrifugal force.
Ans:
17. How do you find thickness of a glass plate by using a screw gauge?
Ans: To find thickness of a glass plate by using a screw gauge.
S1 S2 H
C
P B M
F
★ Find the zero error and zero correction of the given screw gauge.
★ Find the pitch of the screw by using the formula
Distance moved by the screw Pitch of the screw =
Total no. of complete rotations made by the screw.
★ Note the total number of divisions on the head scale. Find least count (L.C.)
of the screw gauge by using the formula.
Centripetal Force
Centrifugal Force
1. It is always directed towards the
centre of the circle.
2. It is associated with an external
agent.
3. It is a real force in an inertial
frame of reference.
4. It is a pull on the body towards the
centre of the circle.
5. It is necessary to make a body to
travel on a curved path.
1. It is directed radially away from
the centre of the circle.
2. It can not be associated with an
external agent.
3. It is a fictitious force in an
inertial frame of reference.
4. It is a tendency of the body to fly
away from the centre of the circle.
5. It comes into play in a rotating
frame of reference.
Pitch of the screw L.C. =
Total no. of divisions on the head scale.
★ Fix the given glass plate tightly between the studs of the screw gauge.
★ Note the pitch scale division that just preceds the edge of the head scale and
take it as P.S.R.
★ Note the division of the head scale that coincides with the index line of the
pitch scale and take it as H.S.R.
★ With the help of zero correction, correct the H.S.R. and take it as C.H.S.R.
★ The thickness of the glass plate can be calculated by using the formula
Thickness = P.S.R. + C.H.S.R. L.C.
★ Repeat the experiment 4 or 5 times and tabulate the results in the given table.
★ The average of the last column of the table gives the thickness of the glass plate.
18. What is magnetic moment? Calculate the value of magnetic induction at a
distance 0.5 m on the axial line of a short bar magnet of length 5 cm. and
pole strength 2 10�3 A-m.
Ans: Magnetic moment: The product of pole strength (m) of a magnet and length of
the magnet (2l) is known as magnetic moment (M) of a magnet.
Length of the bar magnet (2l) = 5 cm = 0.05 m
Polestrength of the magnet (m) = 2 10�3 A-m.
Distance between the mid point of the magnet and the given point (d) = 0.5 m
Magnetic moment M = m 2l = 2 10�3 0.05 = 1 10�4 A � m2.
0 2M 10�7 2 1 10�4 The magnetic induction (B) = . =
4 d3 (0.5)3
= 1.6 10�10 web/m2
S.No.
Object
P.S.R.
H.S.R.
C.H.S.R.
C.H.S.R L.C.
Thickness =
P.S.R. + C.H.S.R. L.C.
1
2
3
4
5
.eenadupratibha
GROUP - B
19. Define ionization energy and explain the factors that influence it.
Ans: Ionization energy: It is defined as the minimum energy required to remove an
electron from the outermost orbital of an atom in gaseous state. Ionization ener-
gy is dependent on nuclear charge, size of the atom, charge on the ion etc.
Nuclear charge: As the nuclear charge increases, the ionization energy
increases. This is due to increase in the attractive force of the nucleus over the
electrons.
Size of the atom: As the atomic size increases, the ionization energy
decreases. This is due to decrease in the attractive force of the nucleus on the
outermost electron which is farther away from the nucleus.
Charge on the ion: As the charge on the ion increases, the ionization energy
increases. For example, the energy required to remove an electron from
unipositive ion is more than the energy required to remove an electron from a
neutral atom.
20. Explain the formation of triple bond with an example.
★ If a molecule contains three bonds between any two atoms of the molecule then
the molecule is said to have a triple bond. Molecules like N2, C2H2, CaC2,
HCN etc. contain triple bond.
★ Let us consider the formation of Nitrogen molecule. The electron configuration
of Nitrogen is 1s2 2s2 2px1 2py
1 2p 1. There are three unpaired electrons one z
each in 2px, 2py and 2pz.
★ 2pz orbital of one Nitrogen atom overlaps end on end with 2pz orbital of
another Nitrogen atom to give rise to a sigma () bond.
★ The remaining two orbitals 2px and 2py are perpendicular to 2pz and also
perpendicular to each other. So they can not overlap end on end.
★ 2px orbitals of two Nitrogen atoms overlap sideways to give rise to a � bond.
★ Similarly 2py orbitals of two Nitrogen atoms overlap sideways to give rise to
anothr bond.
★ Thus a Nitrogen molecule contains a triple bond due to the presence of a
bond and two bonds.
21. Define Molarity. 6 grams of urea is present in 200 ml of its
aqueous solution. Calculate the Molarity of solution. (Molecular weight of
urea is 60)
Ans: Molarity: Molarity is defined as the number of moles or gram moles of a solute
present in one litre of solution.
200 Volume of solution (V) = 200 ml = lit = 0.2 lit.
1000
Weight of urea (W) = 6 gm.
Gram molecular weight of urea = 60 gm.
W 1 6 1 Molarity = = = 0.5 M
gm. mol. wt. V (litres) 60 0.2
22. What are the differences between diamond and graphite.
A: DIAMOND GRAPHITE
1. It is a crystalline hard solid. 1. It is a grayish black soft crystalline solid.
2. Its density is 3.51 gm/c.c. 2. Its density is 2.25 gm/c.c.
3. In this, Carbon atoms are in 3. It contains Carbon atoms in
tetrahedral arrangement. hexagonal rings.
4. C - C bond length is 1.54 A 4. C - C bond length is 1.42 A
5. Bond angle is 10928'. 5. Bond angle is 120.
6. Bad conductor of electricity. 6. Good conductor of electricity.
SECTION - IV
23. Draw a neat diagram of
Nuclear Reactor and
label its parts.
1. Fuel Rods 2. Moderator(water)
3. Control Rods
Schematic Diagram of Nuclear Reactor
24. Draw a neat diagram to show the manufacture of alcohol.
1. Wash
2. Steam
3. Hot Wash
4. Steam and
Alcohol Vapours
5. Condenser
6. 90% Alcohol
7. Waste Materials
Chart showing the alcohol manufacture
PART - B ANSWERS
I. 1) C; 2) D; 3) A; 4) C; 5) D; 6) B; 7) D; 8) B;
9) B; 10) A.
II. 11) 19.6 m/s; 12) Infrared; 13 ) 0.005; 14 ) 4; 15 ) 8O17; 16 ) 7;
17) d � Block; 18) 4; 19) 0.7; 20) Al4C3.
III.
(i) 21-G; 22-E; 23-B; 24-A; 25-C.
(ii) 26-D; 27-C; 28-E; 29-B; 30-A.