31/3/3 2022 Class 10 Science Question Paper Solution
Science
Section A
1.) (a) An electric heater rated 1100 W operates at 220 V. Calculate (i) its resistance, and (ii) the current drawn by it.
Ans: (a) P(Power) = V (Potential difference) × I (Current)
Here P = 1100 W, V = 220 V, I = ?, R = ?
= 2/R
(i) R=v2/p
OR
(b) Calculate the equivalent resistance of the following electric circuit :
Ans:
2.) In the modern periodic table, compare the tendency of the elements to lose electrons while moving
(i) down a group
Ans: Down the group the effective nuclear charge experienced by valence electron is decreasing because the outer most electron are further away from the nucleus. Therefore, these can be lost easily.
(ii) from left to right in a period.
Ans: Effective nuclear charge acting on the valence shell electrons increases across a period. The tendency to lose electron will decrease.
3) Draw two structural isomers of butane.
Ans:
4.) (a) Kulhads (disposable cups made of clay) and disposable paper cups both are used as an alternative for disposable plastic cups. Which one of these two can be considered as a better alternative to plastic cups and why ?
Ans: Disposable paper cups.
- Making of Kulhads on a large scale would result in the loss of fertile top soil. /Disposable paper cups can easily decompose and do not pollute the environment.
OR
(b) Human beings are most adversely affected by the Biological Magnification. State the reason. Why can ordinary washing of the edibles (fruits and vegetables) not reduce the effect of biological magnification ?
Ans: Human beings occupy the top level in any food chain therefore maximum concentration of these chemicals get accumulated in our bodies.
Harmful chemicals or pesticides get absorbed from the soil by the plants along with water and minerals therefore ordinary washing cannot remove these harmful chemicals.
5.) (a) In the given diagram, name the parts where (i) pollen grains are produced, and (ii) pollen grains are transferred.
(b) What happens to ovule and ovary after fertilisation ?
Ans: (a) i) Part—D Anther /Stamen
ii) Part—A Stigma
(b) Ovule converts into Seed; Ovary converts into Fruit
6.) Suggest any two contraceptive methods to control the size of human population and explain them.
Ans: Barrier method : Prevents the meeting of sperms with ova
- Oral pills/Chemical method : Changes the hormonal balance in females so eggs are not released
- Copper T or loop : to prevent pregnancy/to prevent fusion of male & female gametes
Surgical method : To block vas deferens in males or fallopian tube in females to prevent fertilization
7.) (a) Mendel crossed two pea plants with visible contrasting characteristics and found that there were no half-way characteristics in the plants of F1 progeny. Explain the reason for this observation of Mendel.
Ans: No halfway characteristics were found in the F1 generation because the F1 progeny is a mixture of contrasting traits of the parents but only one of the character of the parents gets expressed in F1 progeny.
- The character that gets expressed is a dominant trait and that which does not get expressed in the presence of dominant trait is a recessive trait.
OR
b) Justify the statement “ Sex of the children will be determined by what they inherit from their father “.
Ans: (b) Mother has XX chromosome. Father has XY chromosome. All children inherit X chromosome from mother. The one who inherits X chromosome from father will be a girl and one who inherits Y chromosome from the father will be a boy. /
SECTION B
8) In the following table, some elements have been arranged in a certain pattern :
sa (do) |
re (re) | ga (mi) | ma (fa) | pa (so) | da (la) | ni (ti) |
H | Li | Be | B | C | N |
O |
F |
Na | Mg | Al | Si | P | S |
CI | K | Ca | Cr | Ti | Mn |
Fe |
Co and Ni |
Cu | Zn | Y | In | As | Se |
Br | Rb | Sr | Ce and La |
Zr |
Identify the periodic law with which the given table is associated. List two important features and two anomalies of the above periodic law.
Ans:
- Newland’s Law of Octaves
- Important features :
1.) The elements were arranged in the order of their increasing atomic mass.
2.) Every eighth element has properties similar to the first element.
- Anomalies :
1.) It was assumed that only 56 elements existed in nature and new elements would not be discovered in future.
2.) Unlike elements were put in the same slot/note.
9.) How do Mendel’s experiments show that the traits are inherited independently? Explain .
- Mendel crossed two pea plants with two different visible contrasting characteristics such as plant with round and green seeds, with plant with wrinkled, yellow seeds. In F1 progeny all obtained plants have round and yellow seeds which are dominant characters.
- F1 progeny is self-pollinated to produce F2 progeny and the plant produced in F2 progeny showed new combination such as plant with round and yellow seeds or plant with wrinkled and green seeds which were not present in parent generation or F1 progeny.
The ratio obtained was 9 round yellow, round green, wrinkled yellow, wrinkled green. Thus, traits are independently inherited.
10.) (a) What are decomposers ? State the role of decomposers in the natural replenishment of the soil. (b) Why are decomposers not helpful in decomposing the plastic waste ?
Ans: (a) The microorganisms, that break down the dead remains and waste products of organisms into simpler substances.
Break down the complex organic wastes into simpler substances and return the nutrients to the soil so that these can be used again by the plants.
(b) Decomposers are not able to break down the plastics into its constituents therefore plastics cannot be decomposed. / Plastics are non-bio degradable.
11) (a) State the reason why
(i) carbon compounds have low melting and boiling points.
(ii) carbon compounds do not conduct electricity.
(iii) carbon can form only covalent compounds.
Ans:
(i) The forces of attraction between the molecules are weak.
(ii) Bonding in carbon compounds does not give rise to any charged particles.
(iii) Carbon only shares electrons with other atoms. It is not able to lose four electrons or gain four electrons.
OR
b) What is a homologous series ? Find the difference in molecular mass between the two consecutive members of a homologous series. State how in a homologous series of carbon compounds the following properties vary with increase in molecular mass :
(i) Melting and boiling points
(ii) Chemical properties
Ans:
- A series of compounds in which some functional groups substitute for hydrogen in a carbon chain / the succeeding members differ by -CH2 unit (14 u)
- Difference of CH 12u 2u 14u
(i) Melting and boiling points increase with increase in molecular mass.
(ii) Chemical properties, determined by the functional group remain same in a homologous series.
12.) (a) Draw the pattern of magnetic field lines produced by a current carrying circular loop showing the direction of current in the loop and the direction of the magnetic field lines.
Ans: Pattern of magnetic field
(b) State the rule which can be applied to know the direction of magnetic field lines in the above case.
Ans: Right-hand thumb rule : Hold a current carrying straight conductor in your righthand such that the thumb points towards the direction of current, then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field.
13.) a) In the diagram given below, Coil 1 is connected in series with a battery and a plug key while Coil 2 is connected with a galvanometer.
i) Why does the galvanometer show deflection only when the key (K) is plugged in and not when a steady current starts flowing in the circuit ?
Ans: When the key is plugged-in, current starts in coil-1, the magnetic field around the coil is changed. This produces induced current in the coil – 2 and galvanometer shows deflection
There is no change in magnetic field when a steady current starts flowing in the circuit.
ii) What is observed in the galvanometer, when the key is plugged out ?
Ans: Galvanometer shows deflection in the opposite direction.
iii) State the conclusion based on the observation of this activity.
Ans: Conclusion: Induced current is produced only when there is a change in magnetic field which occurs only when the key is plugged in or plugged out.
OR
(b) In the figure given below, a simple electric motor is shown :
As shown in the figure, the current in the coil ABCD flows from A to B in the arm AB and C to D in the arm CD.
(i) State the directions in which the arms AB and CD will experience a force.
Ans: Arm AB—Downward, Arm CD—Upward
(ii) Identify the part of the electric motor that reverses the flow of current in the coil ABCD and write its name.
Ans: P and Q—Split ring / Commutator
(iii) After the reversal of flow of current in the coil ABCD, state the directions in which the arms AB and CD will experience a force.
Ans: Arm AB upward, Arm CD downward/Direction of force will get Reversed
(iv) Name the rule which is applied to determine the direction of force on a current carrying conductor placed in a magnetic field.
Ans: Fleming’s left-hand rule
14.) Study the following electric circuit in which the resistors are arranged in three arms A, B and C :
(a) Find the equivalent resistance of arm A.
(b) Calculate the equivalent resistance of the parallel combination of the arms B and C.
(c) (i) Determine the current that flows through the ammeter.
OR
(ii) Determine the current that flows in the ammeter when the arm B is withdrawn from the circuit.
Ans:
15.) The modes by which various organisms reproduce depend on the body design of the organisms. In asexual reproduction, a single individual parent produces off springs without the involvement of gametes. This method is a common means of increasing the off springs rapidly under favourable conditions. Asexual reproduction occurs mostly in unicellular organisms, some plants and certain simple multicellular animals.
(a) State the name of the organism in which binary fission takes place in a definite orientation. Also name the disease caused by this organism.
Ans: Leishmania, Kala-azar
(b) List any two advantages of producing plants through vegetative propagation.
Ans: Plants can bear fruits and flowers much earlier than produced by sexual reproduction Plants produced are genetically similar to the parent plant
c) (i) Explain the process of budding in Hydra.
Ans: (i) Bud develops as an outgrowth due to repeated cell division at one specific site, these buds develop into tiny individuals, and when fully mature detach from the parent body and become new independent individuals.
OR
(ii) What happens when
(I) a spirogyra filament matures and attains a considerable length, and
(II) a sporangia in Rhizopus bursts on maturation ?
Ans: (i) The filament breaks into smaller pieces or fragments and each fragment grows into new individuals.
(II) It releases spores which germinate and eventually develops into new Rhizopus individuals.