Key Answer
MGSS
KREIS - SSLC SCIENCE MODEL QUESTION PAPER – 4
Sub: Science Sub. Code: 83E Time: 3.15 Hour Max Marks: 80
PART
A: PHYSICS
I. Four alternatives are given for
each of the following questions/incomplete statements. Choose the correct
alternative and write the complete answer along with its letter of
alphabet. 3 x 1 = 3
(1) What is
the relationship between resistance and current
(a) They
are directly related to each other
(b) They are inversely related to each other
(c) The
resistance has greater magnitude than current
(d) The
current has a greater magnitude than resistance
Ans: (b) They
are inversely related to each other
(2)
Appliances that have metal body are generally connected to the earthing wire
what is the reason to earth these wires ?
(a) To
prevent excess of current
(b) To
prevent the leakage of current
(c) To
prevent extra current to appliance
(d) So
prevent high resistance to the appliance
Ans: b) To prevent the leakage of
current
(3) I dioptre of power of a lens is
equal
(a) 1 m-1 (b) m (c) 1m (d) 1m-2
Ans: (a) 1 m-1
II. Answer
the following. 1X2=2m
(4) The power of lens is -20, what is
focal length ?
Ans:
Power of a lens is -20D, negative sign indicates it is a Concave lens.
Focal length (in
meters)=1/power of
the lens,
Thus, focal length=1/20 = 0.05m = 5cm.
(5) The speed of light in air is 3X108
ms -1 where
as that of the speed of light in water is 2.26 X 108 ms -1 what is the refractive index
of water with respect to air ?
Ans:
Refractive index of water with respect to air =
speed of light in water/speed of light
in air
= 2.26 X 108 ms -1 / 3X108 ms -1
= 1.3
III. Answer the following. 2X3=6m
(6) Draw the ray diagram to show the formation
of image by a convex lens when the object is kept in 2F
Ans:
(7) Study the following electric circuit and find
(a) The current flowing in the circuit and
(b) The potential difference across 10 Ω resistor
Ans:
R = R1 + R2 = 10 + 20 = 30Ω
V = 3 V
(i) From ohm's law V = IR
3 = I × 30 ⇒ I = 3 / 30 = 1 / 10 Ampere or 0.1 A
(ii) Potential difference across 10Ω
resistor
V = IR
= 1 / 10 = 1 volt
(8) Find
the current flowing through the following electric circuit
Ans:
Series combination of 1 Ω and 3 Ω
resistance is in parallel combination with 6 Ω .Their equivalent resistance
is
Now,
3.6 Ω 2.4 Ω and 3 Ω are in series, their
equivalent resistance be
Rs = R1 + R2 + R3 = 3.6 + 2.4 + 3 = 9
Ω
Hence, the current flowing through the circuit is
IV. Answer the following. 3X3=9m
(9) Draw a neat labelled diagram of electric motor.
Ans:
(10) (a) The image of an object placed at60 cm
in front of a lens is obtained on a screen at a distance of 120 cm from it.
Find the focal length of the lens. What would be the height of the image if the
object is 5cm high ?
Ans:
u=−60cm.
OR
(b) List the sign conventions that are
followed in case of refraction of light through spherical lenses. Draw a
diagram and apply these conventions in determining the nature and focal length
of a magnified real image of an object placed 16 cm from the lens.
Ans:
Sign convention for the refraction of
light is as follows.
- All the distances
are measured from the optical centre of the lens.
- All the distances
which are measured in the same direction of the incident light ray (left hand
side of lens) will be taken as positive.
- All the distances
which are measured against the direction of incident light (right hand side)
are taken as negative.
- The perpendicular
distances to principal axis in upward direction will be positive and those in
downward direction will be taken as negative.
Figure below illustrates the
conventions more clearly.
According to the question.
Magnification (m) = -3 (real image is always
inverted).
Object distance (u) = -16cm.
By Magnification Formula;
Magnification, m = v/u
where,
v is the image distance,
u is the object distance
Therefore the focal length is 12 cm.
Since the focal length is positive, therefore the lens is convex lens.
Figure below shows the ray diagram for
the same.
(11) Biogas is an excellent fuel justify the
statement by giving two reasons mention the main constituents of biogas
Ans:
(i) It burns without smoke and leave
no residue therefore causes no atmospheric pollution. (ii)Its heating capacity
is high, i.e. it has high calorific value.
Main constituents of bio gas: Methane,
Carbon dioxide, Nitrogen,
Hydrogen and Hydrogen sulphide
OR
State any three advantages of charcoal over wood.
Ans:
·
Charcoal has a low ignition temperature
or kindling point as compared to wood.
·
Charcoal produces less smoke than wood.
·
Charcoal has a higher calorific value
than wood.
V. Answer the followings: 2X4=8m
(12) Explain the underlying principle and
working of an electric generator.
Ans:
Principle : The electric generator is based on the principle
of electromagnetic induction. When a coil is rotated with respect to a magnetic
field, the number of magnetic field lines through the coil changes. Due to this
a current is induced in the coil whose direction can be found by Fleming’s
right hand rule.
Working : When the armature coil ABCD rotates in a
magnetic field produced by the permanent magnets, it cuts through the magnetic
lines of force.
Due to the rotation of armature coil, the associated magnetic field changes and
an induced electromagnetic force is produced in it. The direction of this
induced electromotive force or current can be determined by using Fleming’s
right hand rule.
In first half cycle the current flows in one direction by brush B1 and
in second it flows in opposite direction by brush B2. This process
continues. So the current produced is alternating in nature.
Functions of Brushes : Brushes
in contact with rings provide the current for external use.
OR
A coil of insulated copper wire is connected
to a galvanometer what will happen if a bar magnet is 1) Pushed into the coil 2) Withdraw from inside the coil 3) Held stationary
inside the coil
Ans:
(i) when magnet is pushed near a bar magnet
then it induces current due to electromagnetic induction.
(ii) When the bar magnet is withdrawn from inside the coil of the insulated
copper wire again the current is induced in the coil but this time it is in
reverse direction.
(iii) When a bar magnet is held stationary inside the coil then no current is
induced that’s why galvanometer will show no deflection.
(13) (a) Write two points of difference
between electric energy and electric power (b) Out of 60w and 40w lamps, which
one has higher electric resistance when in use. (c) What is the commercial unit
of electric energy? Convert it into joules.
Ans:
a) Electrical energy defines
the energy generated
due to the movement of charge carriers in a conductor. While electrical power specifies the rate of consumption of electrical energy by a device.
The SI unit of electrical energy is
Joules. But electrical power is
measured in Watts (or KWh).
b) Resistance and
power are inversely proportional to each other. So, lamp powered 40 W has more resistance than a 60 W lamp.
c) Commercial unit of
electric energy is kilowatt hour(kWh).
PART
B: CHEMISTRY
VI. For
Alternatives are given for each of the following questions/incomplete Sentences.
Choose the correct alternatives and write the complete answer along its letter
of alphabets. Choose the correct answer. 1X3=3m
(14) Most reactive metal among the following
is
(a) Na (b) Mg (c) Zn (d) Cu
Ans: (a) Na
(15) In modern periodic table, as we move from
left to right along the period the metallic nature of the element
(a)
Increases (b) Does
not change
(c) Decreases (d) first
increases & then decreases
Ans: (c)
Decreases
(16) The
image represents a carbon compound Which functional group is present in the
compound?
(a) alcohol
(b) aldehyde (c) ketone (d) carboxylic acid.
Ans: (c) ketone
VII. Answer
the following. 1X3=3m
(17) Why
electric wires are made up of copper?
Ans:
Copper is a good conductor of electricity and it is not much expensive. This is the reason why the electric wires are made of copper
(18) Carbon
from compound mainly by covalent bonding. Give reason for your answer.
Ans:
Carbon forms covalent bonds with other atoms but not ionic
bonds because Losing or gaining 4 electrons is not possible due to energy
considerations in carbon. Hence, it shares electrons to form covalent bonds.
(19) 18th
group elements are called as noble gases why?
Ans:
These elements are
non-reactive and are called noble
gases as they have their outermost orbit complete. Due to stable
electronic configuration they hardly react with other elements.
VIII.
Answer the following. 3X2=6m
(20) Name the aldehyde having four carbon
atoms and write its structure.
Ans:
OR
Explain the
mechanism of cleaning action of soap.
Ans:
Soaps and detergents contain two parts. A long hydrocarbon
part which is hydrophobic (water repelling) in nature and a short ionic part
which is hydrophillic (water attracting) in nature. The hydrocarbon part of the
soap molecule links itself to the oily (dirt) drop and ionic end orients itself
towards water and forms a spherical structure called micelles. The soap
micelles helps in dissolving the dirt in water and wash our clothes.
(21) Draw the diagram of reaction of Zinc
granules with dil H2So4 and testing hydrogen gas by burning
Ans:
(22) Dry
hydrogen chloride gas does not turn blue litmus where as hydrochloric acid why?
Ans:
Acidity is due
to the ability of giving H+ ion. Dry hydrogen chloride does not give hydrogen ions
and so it does not act
as an acid and does not turn blue litmus red.
I X. Answer
the following: 3X3
=9m
(23) Explain about the limitations of
Newland’s law of octaves.
Ans:
·
Law of Octaves only applicable upto calcium and after
calcium every 8th did not possess properties similar to that of the first.
·
later on , several new elements were discovered, whose
properties did not fit into the law of octaves.
· Newlands'law of Octaves worked well with lighter elements only.
(24) Write
the differences between soaps and detergents.
Ans:
|
SOAP |
DETERGENT |
|
1. Sodium salt of Carboxylic acids |
1. Sodium salts of benzene sulphonic
acids. |
|
2. Soaps are bio-degradable |
2. Some detergents are non-
biodegradable |
|
3. Soaps do not lather in hard water |
3. Detergent lather well in hard water |
|
4. Weak cleansing action |
4. Have strong cleansing action |
OR
Why micelle
does form when soap is added to water?
Ans:
Soap molecule has two ends. One end is hydrophilic and
another end is hydrophobic. When soap is dissolved in water and clothes are put
in the soapy solution, soap moleucles converge in a typical fashion to make a
structure, called miceele. The hydrophobic ends of different molecules surroound
a particle of grease and make the micelle, which is a spherical structure. In
this, the hydrophilic end is outside the sphere and hydrophobic end is towards
the centre of the sphere. This is why micelle formation takes place when soap
is added to water.
(25) Draw
the neat labelled diagram of electrolytic refining of copper.
Ans:
X. Answer
the following 1X4=4m
(26) (a)
What is corrosion ? Write the methods to prevent corrosion, which metals do not
corrode easily ?
Ans:
Corrosion is
the process in which metals are eaten up gradually by the action of air,
moisture or a chemical in their surface.
·
By painting.
·
BY applying grease or oil.
·
By tin plating and chromium plating.
·
By alloying it.
Noble metals such
as gold and platinum do not
corrode easily.
(b) What is
an amphoteric oxide? Write the two chemical properties of metals?
Ans:
Amphoteric oxides are the oxides that behave as both acidic
and basic oxides. Amphoteric oxides have properties of acidic as well as
basic oxides that neutralize both acids and bases.
·
Metals are
malleable and ductile.
·
Metals are
good conductors of heat and electricity.
PART
C: BIOLOGY
XI. For
Alternatives are given for each of the following questions/incomplete
Sentences. Choose the correct alternatives and write the complete answer along
its letter of alphabets. Choose the correct answer. 2X1=2m
(27) Which
of these practices can be adopted to save the environment?
(a) Refuse
the use of single - Use plastic bags
(b) Reduce
the use of - paper bags
(c) Recycle
single - use bags
(d) Reduce
- waste food.
Ans: (d) Reduce - waste food.
(28) The
correct sentences which respect to biodegradable substances.
(a) Remain
insert in the environment for a long time
(b) Harm
viruses organisms in the ecosystem
(c)
Increase the density of harmful chemicals in difference topic levels
(d) undergo
recycling neatly in the environment
Ans: (d) undergo
recycling neatly in the environment
XII. Answer
the following: 3X1=3m
(29)
Mention the reason for depletion of Ozone layer
Ans:
The reason for depletion of Ozone layer is Chlorofluorocarbons or CFC. These are released by solvents, spray aerosols, refrigerators, air-conditioners, etc.
(30) Why do
we use fossil fuels judiciously?
Ans:
We need to use fossil fuels judiciously because
they are non-renewable resources. We need to conserve fossil fuels so we don't
run out of them.
(31)
Mention any two problems caused by the constructions of huge dams?
Ans:
·
Economic problems : Construction of dams requires a
huge amount of monetary investments
·
Environmental problems : Construction of dams across
rivers leads to deforestation, which results in the loss of biodiversity. This
disturbs the natural ecosystem.
XIII.
Answer the following: 2X2=4m
(32) How are
involuntary actions and reflex actions differ from each other?
Ans:
Involuntary action is
the set of muscle movement which do not require thinking. But it is controlled
by brain for example beating of heart beat. While on the other hand, the reflex action is rapid and
spontaneous action in
response to any stimulus which doesn't involve brain.
OR
Name the
different types of tropisms exhibited by the plants and write their meaning.
Ans:
The
different types of tropisms are:
(i) Phototropism: The movement of plant parts in response to
light is known as phototropism. The stimulus is light.
(ii) Geotropism: The movement of plant parts in response to
gravity is known as geotropism. The stimulus is gravity.
(iii) Hydrotropism: The
movement of plant parts in response to water is known as hydrotropism. The
stimulus is water.
(iv) Chemotropism: The movement of plant parts in response to chemicals is known as chemotropism. The stimulus is chemicals.
(33) Draw
the diagram showing the longitudinal section of typical flower and label the
parts.
Ans:
XIV. Answer
the following 3X3 =9m
(34) Will
Geographical isolation be a major factor in the speciation of a self
pollination plant species ? why of why not ?
Ans:
In a self-pollinating plant species, geographical isolation
cannot be a major factor in speciation because no new trait can become a part
of the genetic makeup in a self-pollination plant species. However, there are
some chances of some environmental changes which might lead to some variations.
OR How is
the sex of the child determined in human beings?
Ans:
The males have XY sex chromosomes. They produce two types of
gametes having X and Y chromosome. The females have XX chromosome. They produce
only one type of gamete having X chromosome. If sperm is having X chromosome,
then the child will be a girl. If sperm is having Y chromosome, then the child
will be a boy.
(35) What
is the role of seminal vesicle and the prostate gland? What are the functions
performed by the testis in human beings ?
Ans:
Seminal vesicles and prostate gland occur in male
reproductive system. The seminal vesicles and prostate gland add their
secretios to the vas deferens which carries sperms from the testes. The
secretions of seminal vesicles and prostate gland provide nutrition to the
sperms and also make their further transport easier.
Testis are
components of both the reproductive system and the endocrine system. The functions of the testicles are producing sperm and
producing male sex hormones testosterone
OR
What are
the different methods of contraception? What are the functions of placenta?
What are the changes seen in girl at the time of puberty?
Ans:
Barriers, IUDs (IntraUterine Devices), Oral contraceptives, Implants, Injectables,
and surgical methods.
Transmission of nutrients and oxygen from mother to the fetus
and the release of carbon dioxide. The waste materials from the fetus is
excreted through the placenta.
The various changes which
occur in girls at puberty are: Hair grow under armpits and pubic region.
Mammary glands (or breasts) develop and enlarge. Fallopian tubes, uterus and
vagina enlarge. Ovaries start to release eggs. Menstruation (montly periods)
starts.
(36) (a) How are the areas of study of
evolution and classification interlinked ?
(b)
Differentiate between acquired traits and inherited traits.
Ans:
a)
Classification and evolution are highly interlinked fields of study because
the classification of
an organism is influenced by its evolution.
An organism may have a different type of look based on its morphology and are
classified into a different group as compared to the other organism.
b)
XV. Answer
the following 1X4=4m
(37) Draw
the diagram of showing in the longitudinal section of the human brain label the
following parts (a) Pituitary gland (b) Cerebrum
Ans:
XVI Answer
the following 1X5=5m
(38) (a)
What are the components of the transport system in human beings what are
functions of these components ?
(b) How are
waste material excreted in plants ?
Ans:
a)
The main components of the transport system in human beings
are the heart, blood, and blood vessels.
·
Heart pumps oxygenated blood throughout the body. It
receives deoxygenated blood from the various body parts and sends this impure
blood to the lungs for oxygenation.
·
Blood is a fluid connective tissue, it helps in the
transport of oxygen, nutrients, CO2, and nitrogenous wastes.
·
Blood vessels (arteries, veins, and capillaries) carry
blood either away from the heart to various organs or from various organs back
to the heart.
b)
- Plants
produce two gaseous waste products i.e. oxygen during photosynthesis and
carbon dioxide during respiration. Excretion of gaseous waste in plants
takes place through stomatal pores on leaves..
- Excess
of water is also excreted from the plant body through the stomatal pores
and from the surfaces of fruits and stems.
- The
gums, oils, latex, resins, etc. are some waste products stored in plant
parts like barks, stems, leaves, etc. Eventually, plants shed off these
parts.
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