Series JBB/4 Code No. 31/4/1
Set: 1
Q1. Write the number of valence electrons present in a
nitrogen atom (7N14).
Answer: Valence Electron: 5
Q2. Define the term induced electric current.
Answer: Current
produce in a conductor due to change in magnetic flux through the region is
called induced current.
Answer
question numbers 3(a)- 3(d) on the basis of your understanding of the following paragraph and
the related studied concepts:
3(a). State Mendeleev’s Periodic Law.
Answer: "Mendeleev's Periodic law " states that
the physical and chemical properties of an element are the Periodic function of
their atomic masses.
3(b). Why did Mendeleev leave some gaps in the periodic
Table?
Answer: Mendeleev left some gaps in his periodic table
because he believed that in future more elements will be discovered. He
predicted the existence of some elements and named them by prefixing a Sanskrit
numeral, Eka (one).
3(c). If the letter R' was used to represent any of the
elements in the group, then the hydride and oxide of carbon would respectively
be represented as
(1)RH4, RO
(2)RH4, RO2,
(3) RH2, RO2,
(4) RH2, RO
3(d). Isotopes are
(1)Atoms of an element with similar chemical
properties but different atomic masses.
(2)Atoms of different elements with similar
chemical properties but different atomic
masses.
(3) Atoms of an element with different chemical
properties but same atomic masses.
(4)Atoms of different elements with different
chemical properties but same atomic
masses.
Answer: (1)Atoms of an element with similar chemical
properties but
different atomic masses.
Answer
question numbers 4(a)- 4(d) on the basis of your understanding of the following paragraph and
the related studied concepts:
4(a)State two methods of effective plastic waste collection
in your school.
Answer: (i) Making of reusable products such as craft from
the waste.
(ii) we collect the used pen form making useful decorative
items with them.
4(b) Name any two uses of "single-use plastic" in
daily life.
Answer: Single-use plastics, often also referred to as
disposable plastics, are commonly used for plastic packaging and include items
intended to be used only once before they are thrown away or recycled. These
include, among other items, grocery bags, food packaging, bottles, straws,
containers, cups and cutlery.
4(c) If we discontinue of plastic, how we use can an environment-friendly
substitute be provided?
Answer: The best
alternative of plastic by using paper or cloth bag for our daily use such as
shopping, packing etc. Some more alternatives are Stainless steel, Glass,
Fibres like cotton, jute, biodegradable bags can be made by using plant starch,
Wood, etc.
4(d) Do you think microbes will work similarly in landfill
sites as they
work in the laboratory? Justify your answer.
Q5. Which one of the following statements in correct about
the human Circulatory System?
(i)Blood transports only oxygen and not carbon dioxide.
(ii)Human heart has five chambers,
(iii)Valves ensure that the blood does not flow
backwards.
(iv) Both oxygen-rich and oxygen-deficient blood
gets mixed in the heart.
Answer: (iii) Valves ensure that the blood does not flow
backwards.
Q6. Anaerobic process
(A)takes place in yeast during fermentation.
(B)takes place in the presence of oxygen.
(C)produces only energy in the muscles of human
beings.
(D)produces ethanol, oxygen and energy.
Answer: (A)takes place in yeast during fermentation.
OR
Most of the digestion and absorption of the food takes place
in the:
(a)small intestine.
(b)liver.
(c)stomach.
(d) large intestine.
Q7. Fertilization is the process of
(a) transfer of male gamete to female gamete.
(b)fusion of nuclei of male and female gamete.
(c)adhesion of male and female reproductive
organs.
(d)the formation of gametes a reproductive organ.
Answer: (b)fusion of nuclei of male and female gamete.
Q8. If a person has five resistors each of value 1/5 W, then
the maximum resistance he can obtain by connecting them is
The resistance of a resistor is reduced to half of its
initial value. In doing so, if other parameters of the
circuit remain unchanged, the heating effects
in the resistor will become:
(A)two times.
(B)half
(C)one-fourth.
(D)four times.
Q9. Fleming's Right-hand rule gives:
(A) magnitude of the induced current.
(B) magnitude of the magnetic field.
(C) direction of the induced current.
(D) both, direction and magnitude of the induced
current.
Answer: (C) direction of the induced current.
Q10. Which one of the following statements is not true about
nuclear energy generation a nuclear reactor?
(a) Energy is obtained by a process called nuclear
fission
(b) The nucleus of Uranium is bombarded with high energy
neutrons.
(c) A chain reaction is set in the process.
(d) In this process tremendous amount of energy is released
at a controlled rate.
Answer: (b) The nucleus of Uranium is bombarded with high
energy neutrons.
The biggest source of energy on Earth's surface is
(A)Biomass
(B) Solar radiations
(C)Tides
(D)Winds
Q12. Choose the incorrect statement from the following :
(A)Ozone is a molecule formed by three atoms of
oxygen.
(B)Ozone shields the surface of the Earth from
ultraviolet radiations.
(C)Ozone is deadly poisonous.
(D)Ozone gets decomposed by UV radiations.
Answer: Grace one mark to all.
For
question numbers 13 and 14. tvo statements are Biven – one labelled as Assertion (A) and
the other lahelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d)
as given below :
(a)
Both (A) and (R) are true and (R) is the correct explanation of the assertion (A).
(b) Both (A) and (R) are true, but (R) is not
the correct explanation of the assertion
(A).
(c)(A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Q13. Assertion (A) : Following is a balanced chemical
equation for the action of steam on iron :
3Fe + 4H2O ---> Fe3O4
+ 4H2
Reason (R) :The law of conservation of mass
holds good for a chemical equation.
Q14. Assertion (A): The sex of a child in human beings will
be determined by the type of chromosome he/she
inherits from the father.
Reason (R) :A child who inherits X' chromosome
from his father would be a girl (XX),
while a child who inherits a Y chromosome
from the father would be a boy (XY).
Q15. Lead nitrate solution is added to a test tube containing
potassium iodide solution.
(a)Write the name and colour of the compound
precipitated.
(b)Write the balanced chemical equation for the
reaction involved.
(c)Name the type of this reaction justifying
your answer.
(a) Yellow precipitate of lead iodide is formed.
(b)
Pb(NO3)2 + 2KI -----> PbI2 + 2KNO3.
(c)
This is an example of double displacement reaction because ions are exchanged
in this reaction. Also called as precipitation reaction as yellow precipitate
is formed.
What happens when food materials containing fats and oils are
left for a long time? List two observable changes and suggest
three ways by which this phenomenon can
be prevented.
Answer: The food gone rancid because oil and fat oxidized. We
can observe this by:
(i) Bad odour and (ii) bad taste.
This
can be prevented by:
(iii)
Also be prevented by flushing the packet with nitrogen.
Q16. List three differentiating features between the processes
of galvanization and alloying.
Answer:
1 .alloy is a homogeneous mixture of two or more metals or it
is a mixture of a metal and a non-metal
2 .Galvanization is the process of layering a layer of zinc
on the metal
3 .In alloying the two metals or a non-metal or metal needs
to be mixed with each other to make alloy
4 .In galvanization there is no need to make the metal
there's only need to make a layer of zinc on that metal
Compare in tabular form the reactivities of the following
metals with cold and hot water:
(a)Sodium
(b)Calcium
(c)Magnesium
Metal
|
Cold water
|
Hot water
|
Sodium
|
React rapidly to form NaOH
|
React rapidly to form NaOH
|
Calcium
|
React slowly to form Ca(OH)2
|
React rapidly with Ca(OH)2
|
Magnesium
|
Nonreactive
|
React Slowly to form Mg(OH)2
|
Q17. Carbon, a member of group 14, forms a large number of
carbon compounds estimated to be about three million. Why is
this property not exhibited by other
elements of this group ? Explain.
Carbon
has tetravalency, catenation, multiple bond formation and has a rather
average electronegativity. Carbon readily forms covalent bonds to many other
elements. Which enable it to make large number of compound. But
other element of this group cannot show the similar properties because due to
increased size the properties of catenation and multiple bond formation is
reduced.
Q18. A
cheetah, on seeing a prey, moves towards him at a very high speed. What causes the movement of his muscles? How does the chemistry of
cellular components of muscles change during
this event?
Answer:
Nerve Impulse and Structure of Special
Proteins in Muscle Fibre.
On
seeing the prey, an impulse is sent from the brain to the muscles in it’s limbs
so that the cheetah can run towards the prey.
Muscles
have special proteins that change both their shape and their arrangement in the
cells, new arrangement of the proteins give different forms to the muscle
cells, i.e. Shorter or Larger form.
Therefore,
the cheetah is able to run after the prey due to the arrangement of cellular
components (proteins) in the muscles.
Q19.
Define geotropism. Draw a labelled diagram of a plant showing geotropic movements of its parts.
Answer: Gravitropism (also known as geotropism) is a
coordinated process of differential growth by a plant or fungus in response to
gravity pulling on it. It is a general feature of all higher and many lower
plants as well as other organisms. Charles Darwin was one of the first to
scientifically document that roots show positive gravitropism and stems show
negative gravitropism. That is, roots grow in the direction of gravitational
pull (i.e., downward) and stems grow in the opposite direction (i.e., upwards).
This behavior can be easily demonstrated with any potted plant. When laid onto
its side, the growing parts of the stem begin to display negative gravitropism,
growing (biologists say, turning; see tropism) upwards. Hebaverns (non-woody)
stems are capable of a small degree of actual bending, but most of the redirected
movement occurs as a consequence of root or stem growth outside.
[(Optional)
Positive geotropism: The tendency of roots to grow downwards is positive
geotropism. It is seen in all kinds of plants except the ones that grow on
marshy or swampy lands. Roots are an example of positive geotropism.
Negative
geotropism: The negative geotropism is defined as the upward growth of the
plant's part against gravity. The tendency of roots to grow upwards i.e.
against the gravitational pull is also called negative geotropism. Stem or
aerial roots called pneumatophores are examples of negative geotropism.]
Q20.
Define the term evolution. "Evolution cannot be equated with
progress."
Justify this statement.
OR
"During
the course of evolution, organs or features may be adapted for new functions." Explain this fact by choosing an appropriate
example.
Answer: "During the course of evolution, organs or features may be adapted for new functions." The best example is osmoregulation in fishes.
Note: You may also take any other example to explain the same.
Q21. A
concave mirror is used for image formation for different positions of an object. What inferences can be drawn about the following when an object
is placed at a distance of 10 cm from the pole
of a concave mirror of focal length 15 cm
?
(a) Position of the image
(b)Size of the image
(c) Nature of the image
Answer:
A) position of the image:
u= -10cm
f= -15
cm
v= ?
By
mirror formula : 1/f = 1/v + 1/u
B.).
Highly magnified
C.).
Virtual and erect
Q22. The refractive index of a medium x' with
respect to a medium 'y' is 2/3 and the refractive index of
medium 'y' with respect to medium 'z' is 4/3. Find the refractive index of medium 'z' with respect to medium 'x'. If
the speed of light in medium 'x' is 3 x
108 m/s, calculate the speed of light in medium 'y'.
Answer:
It often calculates the change in direction of a ray depends on with the change
in speed of the light. This can be used to calculate refractive Index from
medium Z with respect to X.
xny=
2/3
znx=
9/8
So, the
refractive index of Z with respect to X is 9/8
Velocity
in medium x= 3 x 108 ms-1
speed
of light in medium y is 2×108 m/s.
Q23. A
person may suffer from both myopia and hypermetropia defects.
(a)What is this condition called?
(b)When does it happen?
(c)Name the type of lens often required by the
persons suffering from this defect. Draw
labelled diagram of such lenses.
(a)
Presbyopia or old age defect
(b)
Power of accommodation is reduced due to loss if flexibility of eye lens.
Diagram.
Q24. How
will you use two identical glass prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as
white light ? Draw and label the ray diagram.
Answer:
By using two identical prisms, one placed
inverted with respect to the other we get a narrow beam of white light incident
on one prism emerges out of the second prism as white light.
Q25. A
cloth strip dipped in onion juice is used for testing a liquid X. The liquid X' changes its odour. Which type of an indicator is onion juice?
The liquid X' turns blue litmus red. List the
observations the liquid 'X' will show on
reacting with the following :
(a)Zinc granules
(b)Solid sodium carbonate
Write the chemical equations for the reactions
involved.
Answer:
Onion juice is an olfactory indicator which changes the smell depending on
medium. And X is an acid which changes the smell of onion juice.
(a)
Zn + X
--> H2 + salt of zinc
(b)
Na2CO3 +
X--> CO2 + H2O+ salt of x
[You
may also take x as any acid like HCl]
Define
water of crystallization. Give the chemical formula for two compounds as examples. How can it be proved that the water of crystallization makes a difference in the state and
colour of the compounds?
Answer: Water of crystallization is the number
of water molecules that combine chemically in definite molecular proportion and
provide the colour and structure to the salt, the concerned salt is called as
the crystalline salt.
Copper
sulphate, chemical formula - CuSO4.5H2O has 5 water of crystallization
Washing
soda, chemical formula - Na2CO3.10H2O has 10 water of crystallization.
Q26.
(a)(1) Write two properties of gold which make it the most
suitable metal for ornaments.(2)Name two metals which are the best conductors of heat.
(3)Name two metals which melt when you keep them
on your palm.
(b)
Explain the formation of ionic compound CaO with electron-dot Structure. Atomic numbers of calcium and oxygen are 20 and 8
respectively.
Answer:
(a)(i) Gold is highly ductile and malleable. The property of malleability and
ductility makes it easier to make ornaments.
(ii) Copper
and Aluminium
(b) Following
are the formation of ionic compound .
Q27. (a)Why
is nutrition necessary for the human body ?
(b)what
causes movement of food inside the alimentary canal ?
(c)Why
is small intestine in herbivores longer than in carnivores ?
(d)What
will happen if mucus is not secreted by the gastric glands ?
Answer:(a)
Good nutrition is an important part of leading a healthy lifestyle. Combined
with physical activity, your diet can help you to reach and maintain a healthy
weight, reduce your risk of chronic diseases (like heart disease and cancer),
and promote your overall health.
(b) Peristalsis
mainly causes movement of food inside the alimentary canal. The contraction and
expansion of esophagus is known as Peristalsis movement. In addition other
movements of the stomach and intestines like segmenting movements and sphincter
relaxation also help in propelling food through the alimentary tract.
(c) Cellulose
forms the largest part of the herbivore’s food. Digestion of cellulose takes a
longer time, because the enzymes are produced by the ruminant bacteria that
live in the gut of the herbivore. Longer small intestine ensures that the food
stays for a longer duration and proper digestion is possible. In the case of
carnivores, cellulose is not present in the diet, thus the length of small
intestine is less.
(d) Gastric
glands in stomach release hydrochloric acid, enzyme pepsin and mucus. ... If
mucus is not released, it will lead to erosion of inner lining of stomach,
which may cause acidity and ulcer. Ultimately, mucus provides a protection
against acids and enzymes in the stomach.
Q28. Draw
a neat diagram showing fertilization in a flower and label (a) Pollen tube, (b)
Male germ cell and (c) Female germ cell, on it. Explain the process of fertilization in a flower. What happens to the (i) ovary and (ii) ovule after fertilization ?
In a
process called fertilization, the two gametes join and their chromosomes
combine, so that the fertilized cell contains a normal complement of
chromosomes, with some from each parent flower. The fertilized ovule goes on to
form a seed, which contains a food store and an embryo that will later grow
into a new plant.
Fertilization occurs
when one of the sperm cells fuses with the egg inside of an ovule. After
fertilization occurs, each ovule develops into a seed. Each seed contains
a tiny, undeveloped plant called an embryo. The ovary surrounding
the ovules develops into a fruit that contains one or more seeds.
(a)What
is puberty ?
(b)Describe in brief the functions of the following parts in
the human male reproductive system :
(i)Testes
(ii)Seminal vesicle
(iii)Vas deferens
(iv)Urethra
(c)Why are testes located outside the abdominal cavity ?
(d)State how sperms move towards the female germ cell.
Answer:
(a) Puberty is the process(stage of life in which) of physical changes through which
a child's body matures into an adult body capable of sexual reproduction. It is
initiated by hormonal signals from the brain to the gonads: the ovaries in a
girl, the testes in a boy.
(b) (i)Testes
produces testosterone which regulate the formation of semen and for the
development of male characteristics
(ii)Seminal
vesicles secrete fluids onto the sperms for ease of transport and nutrition
(iii)Vas
deferens transports the sperms from testicles to the urethra for ejaculation
(iv)Ureter
brings the urine from the kidneys to the urinary bladder.
(c)
A
pair of testes is located outside the abdominal cavity because spermatogenesis
occurs at a temperature which is two to three degrees Celsius lower than the
body temperature.
(d) Sperm
are made in the testes and mature in a coiled tube, the epididymis. At the end
of sexual intercourse, they travel along the vas deferens and mix with fluids
made by the prostate gland and seminal vesicle. The sperm then pass along the
urethra to the tip of the penis and into the female vagina.
Q29. Draw
a schematic diagram of a circuit consisting of a battery of 3 cells of 2 V
each, a combination of three resistors of 10 W, 20 W and 30 W connected
in parallel, a plug key and an ammeter, all connected in series.
Use
this circuit to find the value of the following
(a)Current
through each resistor
(b)Total
current in the circuit
(c)Total
effective resistance of the circuit.
Two
identical resistors, each of resistance 15 W, are
connected in (i) series, and (ii) parallel,
in turn to a battery of 6 V. Calculate the ratio of the power consumed in the
combination of resistors in each case.
Q30.
(a)State Fleming's Left-hand rule.
(b)List three characteristic features of the electric
current used in our homes.
(c)What is a fuse? Why is it called a safety device?
(d)Why is it necessary to earth metallic electric
appliances?
Answer:
(a) Fleming's left hand rule states that if the thumb, forefinger and the
middle finger are stretched mutually perpendicular to each other than the thumb
represents the direction of force. The forefinger represents the direction of
magnetic field and the middle finger represents the motion or direction of the
induced current
(b) Alternating
current, Frequency 50Hz and Voltage 220V.
(c) A
fuse is an electrical safety device that has the capability to protect an
electric circuit from excessive electric current. It is designed to allow
current through the circuit, but in the event that the current exceeds some
maximum value it will open, severing the circuit.
(d) The
metallic body of electric appliances is connected to the earth wire so that any
leakage of electric current is transferred to the ground. This prevents severe
electric shock to the user. That is why earthling of the electrical appliances
is necessary.
