31/2/3 2022 Class 10 Science Question Paper Solution
SECTION A
1.) (i) Write the electronic configuration of element X, given by its symbol as under:
Ans: X – 2, 8, 8, 2
(ii) Determine its position in the modern periodic table.
Ans: Group – 2; Period – 4
(iii) What is the nature of its oxide?
Ans: Basic
(iv) Name one other element of its group.
Ans: Beryllium / Magnesium / Strontium / Barium
2.) (i) Write the name and draw the structure of a saturated hydrocarbon with four carbon atoms.
Ans:
(ii) Write the number of single covalent bonds present in this compound.
Ans:
No. of bonds 13 / No. of bonds 13 / No. of bonds 12
3.) (a) Name the reproductive and non-reproductive parts Of bread mould (Rhizopus).
Ans: Reproductive part of bread mould—Sporangia / Spores
Non-reproductive part of bread mould—Hyphae
(b) List any two advantages of vegetative propagation.
Ans:
(i) Plants raised by vegetative propagation can bear flowers and fruits
much earlier than those produced from seeds.
(ii) It is important for plants that have lost the capacity to produce
seeds.
(iii) All plants formed by this method are genetically similar to the
parent plant and have all its characteristics.
4.) (a) State one drawback of each of the following:
(i) Oral contraceptive pills
Ans: change hormonal balance leading to side effects/cause hormonal
imbalance
(ii) Copper-T
Ans: Irritation in the uterus
(b) Under which category of contraceptive methods, is the use of condom kept? In what way, its use is better as compared to other methods of contraception?
Ans:
- mechanical barrier
- Prevents transmission of infections like STD’s
5.) (a) Name the poles P, Q, R and S of the magnets in the following figures ‘a’ and ‘b’ :
Ans:
(b) State the inference drawn about the direction of the magnetic field lines on the basis of these diagrams.
Ans: The magnetic field lines emerge from the North-pole and merge to South-pole outside the magnet. (Inside the magnet the direction is from South pole to North pole.)
Alternative answer :-
Closed curves which emerge from North pole and merge at the South pole.
OR
When is the force experienced by a current carrying straight conductor placed in a uniform magnetic field.
(i) Maximum
Ans: Maximum – when the direction of current (current carrying conductor)
is perpendicular to the direction of magnetic field.
(ii) Minimum?
Ans: Minimum – (zero) when the direction of current (current carrying
conductor) is parallel / antiparallel / along the direction of magnetic
field.
6.) In the following food chain, only 2J of energy was available to the peacocks. How much energy would have been present in Grass ? Justify your answer.
Ans:
- 20,000 J
- Only 10% usable energy / amount of organic matter is transferred from
one trophic level to the next higher trophic level in a food chain and rest
90% is lost to the environment as heat.
OR
(a) What is meant by garbage ? List two classes into which garbage is classified.
Ans:
- Waste material generated in day-to-day lives.
- Biodegradable and Non-biodegradable substances.
(b) What do we actually mean when we say that the “enzymes are specific in their action” ?
Ans: Specific enzymes are needed for the breakdown of a particular /
specific substance.
7.) Name the reproductive parts of an angiosperm. Where are these parts located ? Explain the structure of its male reproductive part.
Ans:
- Stamen
- Pistil / Carpel
- Located in the flower
- The male reproductive part consists of anther and filament .
(give full credit to labelled diagram of stamen)
OR
What is puberty ? Mention any two changes that are common to both boys and girls in early teenage years.
Ans: The stage at which rate of general body growth begins to slow down and the reproductive tissues begin to mature.
Two common changes
(i) Thick hair growing in armpits and genital area.
(ii) Skin becomes oily.
(iii)Thin hair on legs and arms.
SECTION B
8.) Consider the following organic compounds
(a) Name the functional group present in their compounds.
Ans: Aldehyde
(b) Write the general formula for the compounds of this functional group.
Ans: CnH2n+1CHO / R − CHO
(c) State the relationship between these compounds and draw the structure of any other compound having similar functional group.
Ans: They are homologues.
OR
(a) Draw the electron dot structure for ethyne.
Ans:
(b) List two differences between the properties exhibited by covalent compounds and ionic compounds.
Ans:
Covalent Compounds |
Ionic Compounds |
low melting point |
high melting point |
low boiling point. |
high boiling point. |
poor conductors of electricity. |
good conductors of electricity in molten state or aqueous solution. |
9.) (a) State Newland Law of Octaves.
Ans: “When the elements are arranged in the order of their increasing
atomic masses, then every eighth element has properties similar to the
first element.”
(b) With an example, explain Dobereiner’s Triads.
Ans: When the elements of a triad are arranged in the order of their
increasing atomic masses, the atomic mass of the middle element is
equal to the average of the atomic masses of other two elements.
Examples:
(c) List one limitation each of both the attempts mentioned in ‘a’ & ‘b’.
Ans: Limitations of :-
- Newlands’ Law : Applicable till Calcium / assumed that only 56
elements existed / unlike elements placed in the same column (Co,
Ni). - Dobereiner’s Triads : Only three triads were formed.
10.) (a) What is the heating effect Of electric current?
Ans: When an electric current is passed through a conductor, it becomes hot
because the source energy is dissipated in the form of heat. This
phenomenon is known as heating effect of electric current.
(b) Write an expression for the amount of heat produced in a resistor when an electric current is passed through it stating the meanmngs of the symbols used.
Ans:
H = Amount of heat produced
R = Resistance
I = Current
t = Time
V = Potential Difference
(half marks for writing meaning of symbol
(c) Name two appliances based on heating effect of electric current.
Ans: Electric iron, geyser, heater
11.) What are Chromosomes? Explain how stability of the DNA of the species is ensured in sexually reproducing organisms.
Ans:
- Thread-like structures present in the nucleus carrying genetic
material. - Each cell will have two copies of each chromosome, one each from
the male and female parents. Every germ cell will take one
chromosome from each pair. - When two germ cells combine, they restore the number of
chromosomes, ensuring the stability of the species.
12.) (a) We do not clean ponds or lakes, but an aquarium needs to be cleaned regularly. Why?
Ans: A pond is a natural ecosystem having its own cleaning system in the
form of decomposers whereas an aquarium is a man-made or artificial
ecosystem having no decomposers.
(b) Why is ozone layer getting depleted at the higher levels of the atmosphere? Mention one harmful effect caused by its depletion.
Ans:
- It is due to release of chlorofluorocarbons (CFCs) in the atmosphere.
- The harmful UV radiations would reach earth and cause damage to
different life forms on the earth / cause skin cancer in human beings.
13.) (a) List the factors on which the resistance of a uniform cylindrical conductor of a given material depends.
Ans:
(i) Length of the conductor (l)
(ii) Area of cross-section of the conductor (A)
(b) The resistance of a wire of 0.01 cm radius is 10 Ω. If the resistivity of the wire is 50 x 10-8 Ω m, find the length of this wire.
Ans:
OR
(a) What is the meaning Of electric power Of an electrical device ? Write its SI unit.
Ans: Rate at which electric energy is dissipated / consumed in an electric circuit
SI unit : watt joule per second volt . ampere
(b) An electric kettle of 2kW is used for 2h. Calculate the energy consumed in
(i) kilowatt hour and (ii) joules.
Ans:
E = P × t
(i) 2 kW × 2h = 4kWh
(ii) 4 × 3.6 × 106 joules = 14.4 × 106 J / 1.44 × 107 J
SECTION C
14.) A student was asked to perform an experiment to study the force on a current carrying conductor in a magnetic field. He took a small aluminum rod AB, a strong horse shoe magnet, some connecting wires, a battery and a switch and connected them as shown. He observed that on passing current, the rod gets displaced. On reversing the direction of current, the direction of displacement also gets reversed. On the basis of your understanding of this phenomenon, answer the following questions:
(a) State the condition under which the displacement of the rod is largest for the same magnitude of current flowing through it.
Ans: Direction of current in the rod is perpendicular to the direction of
magnetic field.
(b) State the rule that determines the direction of the force on the conductor AB.
Ans: Fleming’s left-hand rule : Stretch the thumb, forefinger and middle finger of your left-hand such that they are mutually perpendicular. If the first finger points to the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.
(c) (i) If the U shaped magnet is held vertically and the aluminum rod is suspended horizontally with its end B towards due north, then on passing current through the rod from B to A as shown, in which direction will the rod be displaced ?
(ii) Name any two devices that use current carrying conductors and magnetic field.
Ans: (i) Towards left or towards west / Into U shape magnet
(ii) Electric motor/ electric generator/ loudspeakers/ microphones/
electrical measuring instruments
OR
Draw the pattern of magnetic field lines produced around a current carrying straight conductor held vertically on a horizontal cardboard. Indicate the direction of the field lines as well as the direction of current flowing through the conductor.
Ans:
Direction of current – downward
Direction of field lines – clockwise
Alternatively, If the direction of current is marked upwards then direction of field lines will be anticlockwise.
(Credit full marks if direction of current and field lines are marked in the
diagram
15.) Mendel blended his knowledge of Science and mathematics to keep the count of the individuals exhibiting a particular trait in each generation. He observed a number of contrasting visible characters controlled in pea plants in a field. He conducted many experiments to arrive at the laws of inheritance
(a) What do the Fl progeny of tall plants with round seeds and short plants with wrinkled seeds look like?
Ans: Tall with round seeds
(b) What are recessive traits?
Ans: Short with wrinkled seeds / Recessive traits are those traits which are
not expressed in the presence of dominant trait.
(c) Mention the type of the new combinations of plants obtained in F2 progeny along with their ratio, if Fl progeny was allowed to self pollinate
Ans: Tall with wrinkled seeds : Short with round seeds
3 : 3
1 : 1
OR
If 1600 plants were obtained in F2 progeny, write the number of plants having traits :
(i) Tall with round seeds
Ans: 900
(ii) Short with wrinkled seeds
Write the conclusion of the above experiment.
Ans: 100
- When two individuals showing two different contrasting characteristics are bred with each other, then in F2 progeny new combinations are seen / visible as traits are independently inherited.