Thursday, February 7, 2013

SAMPLE QUESTIONS SCIENCE (086) CLASS – IX S.A. – II (2012-13)

VSA

Ques. 1 Find the ratio by mass of the elements present in molecule of ammonia (NH3).Given that, atomic mass N=14, H=1

Que. 2 Write the electronic configuration of an element whose atomic number is 12.

Que. 3 A student picks up four books from the floor, walks across the room through some distance with the books at the same height and then keeps these books at the new place. In which of these sequence of actions work is said to be performed ?

Que. 4 A body is fully immersed in water to a depth of 2m, 4m and then 5 m, in turn. Will the loss in its weight be equal or different in three cases? If different, in which case will it be least ?


ANSWER KEY

Ans. 1
N : N (Ratio by mass) 1
14 : 3 x 1 14 : 3
Ans.2
K , L , M 1
2 , 8 , 2
Ans. 3
When the student is picking up books from the floor in the beginning.
Ans.4
Equal

SA I

Que. 5
Calculate the number of moles for 60g of He (finding mole from mass). Given, atomic mass of He = 4u

Que. 6
Write chemical formulae of
(i)Hydrogen sulphide (ii) Iron s(II) chloride

Que. 7
List any two practices you would like to follow in order to maintain good health.

Que. 8
The volume of a body of mass 50 g is 20 cm3. If the density of water is taken as 1 gcm-3, will the substance float or sink in water? Why?

Que. 9
Which wave characteristics determine the
(a) Loudness (b) pitch of sound?

Draw two different waveforms and mark these characteristics on it.

ANSWER KEY

Ans. 5
Atomic mass of He = 4 u (2)
Molar mass of He = 4g
Given mass m 60
Thus, number of moles = -------------------- = n = ----- = ------- = 15
Molar mass M 4
Ans. 6
(i) H2S (ii) FeCl2 (1+1)
Ans. 7
Balanced diet, personal and community hygiene, congenial environment (any two) (1+1)
Ans. 8
It will sink. The weight of the body is greater than the weight of water displaced by it.
Ans. 9
(a) amplitude
(b) Frequency

SA II

Que. 10 List any three distinguishing features between the models of an atom proposed by J.J Thomson and Ernest Rutherford.

Que. 11 Calculate the mass percentage of oxygen present in the following compounds and state the law of chemical combination associated. Given, H=1, O=16.
(i) Water (H2O) and (ii) Hydrogen peroxide (H2O2)

Que. 12 List in tabular form, three distinguishing features of dicot plants with monocot plants.

Que. 13 State the meaning of immunisation. Mention the principle on which it is based. List two diseases for which vaccines are provided under public health program.

Que.14
(a) Give one example of each of the following:
(i) Small mass but high kinetic energy (i) Large mass but low kinetic energy
(b) Prove mathematically that the total mechanical energy of a freely falling body in air is conserved.

Que.15 Write full form of acronym SONAR. Explain how the method of echo-ranging is used to determine the depth of sea.

ANSWER KEY

Ans. 10
J. J. Thomson Model of atom Rutherford’s Model (1+1+1)
Plum pudding model
Nucleus (+ charge) in centre
+ charge place ‘Kernels’
Electron revolve in orbits
- charge embedded on it
Most of the space is empty
Ans. 11

Law of multiple proportions
H2O % of O = 16/18 X 100
H2O2 % of O = 32/34 x 100
Ans. 12

MONOCOTS
DICOTS
Posses 1 cotyledon
Fibrous roots
Parallel venation
Trimerous Flowers
Possesses two cotyledons
Taproots
Reticulate venation
Pentamerous flowers
(any three) (1+1+1)
Ans. 13

Process of developing artificial immunity in a person by giving biological preparations is known as immunisation. When immune system first sees the microbe it responds against it and remembers it specifically, so next time it responds with even greater vigour. Tetanus / Whooping cough / Diphtheria/ Measles are some of the common diseases, against which, the vaccines are provided under public health program. (1+1+½+½)(3)

Ans. 14
(a) (i) A cricket/hockey ball which has been hit hard and is travelling fast.
(ii)A shot put thrown by an athlete.
(b) Let the body of mass m at height h above the ground starting from rest, be falling freely.

Total energy of the body at height h is =mgh (PE) + o (KE) = mgh
After the body has fallen freely through
a distance x (say), K.E.= mgh, P.E.=mg (h-x)
Total energy = K.E. + P.E., mgh+mg (h-x)=mgh
When it reaches the ground K.E. =½m 2gh= mgh
P.E.=0, Total Energy = K.E. + P.E. =mgh
Thus the total mechanical energy, which is the sum of K.E. and P.E. is always equal to mgh.
Ans. 15
Sound Navigation And Ranging: A Transmitter producing ultrasonic waves is fitted at the bottom of a ship or a boat. The ultrasound waves emitted by the transmitter go to the bottom of the sea and get reflected from the bottom. These are received back by a detector also fitted at the bottom. Knowing the time elapsing between sending and receiving back of the ultrasonic waves and the speed of these waves in water, the depth of sea can be calculated.

L.A.

Que. 16
i) State the method of determining the valency of an element if its atomic number is given.
ii) Determine the valency of the following elements, the atomic numbers of which are given in parenthesis:- Chlorine (17)- Sulphur (16)- Aluminium(13)
Que. 17
(i) List three characteristics which help us to distinguish amphibian to pisces.
(ii) Classify the following living organisms as cold blooded and warm blooded animals: Shark, Lizard, Sparrow, Rohu.
Que. 18
(a) Explain, with the help of an example the difference between the terms. Thrust and pressure. Which one of the two has same SI unit as that of Force?
(b) Consider a wooden block of mass 5 Kg and dimensions 40 cm X 20cm X 10 cm with its faces 20cmX10cm and 40cmX20cm kept on the table, in turn. In which case will the pressure exerted by the box on the table be more? Justify your answer by doing mathematical calculations.

ANSWER KEY

Ans. 16
(i) The number of electrons gained, lost or shared to make the octet of electrons (in the outermost shell), gives us directly the combining capacity of the element, that is, the valency. (2)

(i) Chlorine = atomic no. 17, electronic configuration = 2,8,7 valency = -1 (1)
Sulphur = atomic no. 16 electronic configuration = 2,8,6valency = -2 (1)
Aluminium = atomic no. 13 electronic configuration = 2,8,3 valency = +3 (1)
Ans. 17
(1) Amphibians lack scales, have mucous glands, have a three chambered heart (1+1+1)
(ii) Cold blooded – Shark Rohu, Lizard (½+½+½)
Warm blooded – sparrow (½)
Ans. 18
(a) Pressing the flat end of a ball point pen against the hand with some force and pressing the pointed tip of the same pen against the hand with the same force. Pressing on pointed tip produces greater pain because the area on which same force acts decreases and the effect of this force increases.
The total force acting on an area is called Thrust whereas the force acting per unit area is called pressure.-Thrust has the same SI Unit of Newton as Force.
(b) The pressure exerted will be more when the block with its face. 20cmX 10 cm is kept on the table. This is equal to 2450 Nmˉ². When the block is kept on the table with its face 40 cmX20cm, the pressure is equal to 612.5 Nmˉ².

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