31/4/2 2022 Class 10 Science Question Paper Solution
SECTION A
1.) Mention the functions of
(a) Placenta
Ans: Placenta—Helps in the transportation of glucose and oxygen from the mother to the embryo/ removal of waste
(b) Fallopian tubes
Ans: Egg is carried from the ovary to uterus / site of fertilisation
(c) Uterus
Ans: Helps in the development of embryo/ implantation
(d) Ovary in the human female reproductive system.
Ans: Production of female gamete or ovum/secretion of female sex hormone
2.) Using height (tallness / dwarfness) of a plant as an example, show that genes control the characteristics or traits in an organism.
Ans:
- The plants have genes which have the ability to produce enzyme for
growth. If enzymes are efficient more growth hormone are produced thus
plant grow in length. - If the gene for that enzyme has an alteration that makes the enzyme less
efficient, the amount of hormone produced will be less and a plant will be
short.
OR
In a cross between red coloured and white coloured flowers, when plants with red coloured flowers of Fl generation were self pollinated, plants of F2 generation were obtained in which 75% of plants were with red flowers and 25% plants were with white flowers.
Ans:
75%—Red (RR and Rr) flowers
25%—White flowers (rr)
OR
Explain the inheritance of traits in the above cross with the help of a flow chart only along with the ratio of plants obtained.
Ans:
Ratio—3 : 1
Red : White
3.) Consider the following molecular formulae of carbon compounds:
(i) CH3COOH (ii) CH3OH (iii) C2H6 (iV) C3H4 (V) C4H8
(a) Which one of these compounds belongs to homologous series of alcohols?
Ans: CH3OH
(b) Identify the compound having triple bond between carbon – carbon
Ans: C3H4
(c) Write the molecular formula of the first member of the homologous series to which CH3COOH belongs.
Ans: HCOOH
(d) Write the general formula of the series to which the compound C4H8
belongs.
Ans: CnH2n
4.) “The improvement in our lifestyle has led to the generation of large amount of waste material.” List two reasons to justify this statement.
Ans:
- Improvement in lifestyle has led to large consumption of resources
- Demand for things with disposable nature increases the nonbiodegradable wastes like plastics, metal cans etc.
OR
“The change in packaging has resulted in waste becoming non biodegradable .” Giving two examples from daily life, justify this statement.
Ans:
- The demand for increasing the shelf life of products and transporting
goods over large distances is increasing, so the plastics / polyethene
packing is preferred. - Less use of biodegradable products such as paper bag, cloth bag etc.
5.) What is Regeneration? Explain the process of regeneration in Planaria.
Ans:
- The process in which an individual is cut or broken up into many pieces and many of these pieces grow into separate individual.
- In Planaria regeneration is carried out by specialised cells, these cells proliferate, develop and differentiate into various cell types and tissues.
6.) As shown in the diagram an aluminium rod ‘AB’ is suspended horizontally between the two poles of a strong horse shoe magent in such a way that the axis of rod is horizontal and the direction of the magnetic field is vertically The rod is connected in series with a battery and a key.
(a) What is observed when a current is passed through the aluminum rod from end B to end A ?
Ans:
- Rod AB would get displaced
- Reason: When a current carrying conductor is placed in an
external magnetic field perpendicularly, it experiences a force.
(b) What change is observed in a situation in which the axis of the rod ‘AB’ is moved and aligned parallel to the magnetic field and current is passed in the rod in the same direction?
Ans: As current and magnetic field are parallel, there will be no force experienced by the conductor hence no displacement in rod.
OR
“Magnetic field is a physical quantity that has both direction and magnitude.” How can this statement be proved with the help of magnetic field lines of a bar magnet?
Ans:
- Field lines emerge from the north pole and merge at south pole/the
direction in which a north pole of the compass needle moves inside it. - The relative strength of the magnetic field is shown by the degree of
closeness of the field lines. Crowded are the field lines, stronger is the
field.
OR diagrammatic expression.
7.) State Modern Periodic Law. How many rows and columns are there in the Modern Periodic Table?
Ans: Properties of elements are a periodic function of their atomic number
‘18’ vertical columns called groups
‘7’ horizontal rows are known as periods
SECTION B
8.) An electric motor rated 1100 W is connected to 220 V Find :
(i) The current drawn from the mains,
(ii) Electric energy consumed if the motor is used for 5 hours daily for 6
(iii) Total cost of energy consumed if the rate of one unit is t
Ans:
Power (P) = 1100 W, V = 220 V
(i)
(ii) E = P × t
= 1100 W × 5 h × 6 = 33000 Wh
(iii) Cost of one commercial unit = ₹ 5
Energy consumed = 33 kWh = 33 unit = 118.8 × 106 J
Cost of 33 unit = 33 × 5 = ₹ 165
OR
Study the following circuit and find :
(i) Effective resistance of the circuit
Ans: Effective resistance of the circuit
(ii) Current drawn from the battery
Ans: Current drawn from the battery
(iii) Potential difference across the 5 Ω resistor
Ans:
(9) You are provided with a resistor, a key, an ammeter, a voltmeter, four cells of 5 V each and few connecting wires. Using these circuit components, draw a labelled circuit diagram to show the setup to study the Ohm’s law.
State the relationship between potential difference (V) across the resistor and the current (I) flowing through it. Also draw V-I graph, taking Von the X-axis.
Ans: Electric circuit
Diagram making
Any two labelling
Potential difference (V) directly proportional to the current (I).
10.) “Two different forms of carbon – diamond and graphite have different structures and very different physical properties even though their chemical properties are same.” Explain why.
Ans:
- In diamond, each carbon atom is bonded to four other carbon atoms forming a rigid three dimensional structure. This makes diamond the hardest substance known.
- In graphite, each carbon atom is bonded to three other carbon atoms in same plane giving a hexagonal array being placed in layers one above the other this makes graphite a smooth and slippery substance.
- Both diamond and graphite are composed of carbon, therefore their chemical properties are same. / Both are allotropic form of Carbon.
OR
State the reasons, why carbon cannot
(i) Lose four electrons to form C4+ cation, and
Ans: If carbon atom loses four electrons forming C4+ cation, it would require a
large amount of energy to remove four electrons leaving behind a carbon
cation with six protons in its nucleus holding two electrons.
(ii) Gain four electrons to form C4– How does carbon overcome this problem to form compounds?
Ans: If carbon atom gains four electrons forming C4– anion, it would be difficult for a nucleus with six protons to hold on ten electrons, that is four extra electrons.
- Carbon atom overcomes this problem by sharing its valence electrons with other atoms of carbon or with atoms of other elements.
11.) In flowering plants, the pollen grams are transferred to stigma by pollination but the female germ cells are present in the ovary. Explain with the help of a labelled diagram (only concerned parts), how the male germ cell reaches the ovary.
Ans: After the pollen lands on a suitable stigma, it has to reach the female germ cells
which is located in the ovary. For this a tube grows out of the pollen grain and
travels through the style to reach the ovary.
Labelling: pollen tube/ ovary/ male germ cell
12.) Name the elements whose compounds formed the basis of classification in Mendeleev’s periodic table. Why did Mendeleev choose these elements?
How the formulae of these compounds had helped Mendeleev in deciding the position of an element in his periodic table ?
Ans:
- Hydrogen and Oxygen
- He selected hydrogen and oxygen as they are very reactive and formed compound with most of the elements.
- The formulae of hydrides and oxides formed by an element were treated as one of the basic properties of an element for its classification.
13.) Draw a diagram showing flow of energy from solar input to a food chain having four trophic levels in an eco List two inferences that can be drawn from the energy flow diagram.
Ans: Diagram
(Can be shown with the help of food chain starting from sun)
Inferences:
- Flow of energy is unidirectional
- Sun is the ultimate source of energy.
- Energy available at each trophic level gets diminished progressively due to loss of energy at each level.
- Every food chain starts with producers.
SECTION C
14.) AB is a coil of copper wire having a large number of The ends of the coil are connected with a galvanometer as shown. When the north pole of a strong bar magnet is moved towards the end B of the coil, a deflection is observed in the galvanometer.
(a) State the reason for using galvanometer in the activity and why does its needle deflects momentarily when magnet is moved towards the coil.
Ans:
- Galvanometer is used to detect the presence of current along with its direction.
- Needle deflects momentarily due to momentary change in magnetic field associated with the coil due to which current induces.
(b) A deflection in the galvanometer is also observed when the magnet is held stationary and the coil is moved towards the south of pole of the magnet. Why?
Ans: When coil moves towards the magnet, the magnetic field passing through
coil changes and a current is induced in the coil due to which deflection
is observed in galvanometer.
(c) State the conclusion that can be drawn from this activity. Will there be any change in the momentary deflection m the galvanometer if number of turns in the coil is increased and a more stronger magnet is moved towards the coil?
Ans:
- The relative motion of a magnet and coil produces an induced potential difference which sets up an induced current in the circuit and it lasts so long the relative motion is there.
- Momentary deflection will be there with increased magnitude.
OR
What is electromagnetic induction ? What is observed in the galvanometer when a strong bar magnet is held stationary near one end of a coil of large number of turns? Justify your answer.
Ans:
- It is a process by which a changing magnetic field in a conductor induces current in another conductor.
- No deflection in galvanometer As there is no relative motion between the coil and magnet which leads to no change in magnetic field associated with coil hence no induced current generates.
15.) Sex of an individual is determined by different factors in various species. Some animals rely entirely on the environmental cues, while in some other animals the individuals can change their sex during their life time indicating that sex of some species is not genetically determined. However, in human beings, the sex of an individual is largely determined genetically.
(a) In what way are the sex chromosomes ‘X’ and ‘Y’ different in size? Name the mismatched pair of sex chromosome in humans.
Ans:
- X chromosome is of normal size and Y chromosome is short / Y chromosome is shorter than X chromosome.
- XY pair of chromosomes
(b) Write the number of pair/pairs of sex chromosomes present m human In which one of the parent (male/ female) perfect pair / pairs of sex chromosomes are present?
Ans:
- One pair of sex chromosomes
- mother/female has perfect pair of chromosomes
(c) Citing two examples, justify the statement “Sex of an individual is not always determined genetically”.
Ans:
- In reptiles, the temperature at which fertilized eggs are kept determines
whether the animals developing in the eggs would be a male or a female. - In snails, they can change their sex during their lifetime.
OR
Draw a flow chart to show that sex 1s determined genetically m human beings.
Ans: