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.