Question 1

Question 7(a)What is ozone ? How is it formed in the upper layers of the Earth's atmosphere ? How does ozone affect our ecosystem ?

Accepted Answer

Ozone is a gas which is formed when an oxygen molecule (O2) combines with another oxygen atom (O). Thus, Ozone (O3) is a molecule formed by three atoms of oxygen.At the higher levels of the atmosphere, UV radiation acts on oxygen (O2) molecule. The higher energy UV radiations split apart some molecular oxygen (O2) into free oxygen (O) atoms. These atoms then combine with the molecular oxygen to form ozone.O2 →UV{\xrightarrow{	ext{UV}}}UV​ O + OO2 + O ⟶ O3Ozone is present at the higher levels of the atmosphere and it shields the surface of the earth from ultraviolet (UV) radiation of the Sun. Therefore, it helps to protect all ecosystems/organisms from highly damaging radiations that can cause problems like skin cancer and cataract in humans and potential damage to some marine organisms and plants. Ozone also helps to maintain the temperature of earth.

Question 2

Question 7(b)(i) List two human-made ecosystems.(ii) "We do not clean a pond in the same manner as we do in an aquarium." Give reason to justify your answer.

Accepted Answer

(i) Two human-made ecosystems are:Agricultural fieldAquarium(ii) Pond has a natural ecosystem. It has many decomposers present in it due to which the pond is naturally cleaned up. It is a balanced and self sustaining ecosystem. An aquarium, however is not self sustaining. We need to clean it up and change its water in order to remove the waste produced by the fishes or the leftover food in there as these may further act as toxins for water and aquatic life.

Question 3

Question 9(b)(i) Write the molecular formula of benzene and draw its structure.(ii) Write the number of single and double covalent bonds present in a molecule of benzene.(iii) Which compounds are called alkynes ?

Accepted Answer

(i) Molecular formula of benzene — C6H6Structure of benzene:(ii) In the structure formula of benzene there are 3 double bonds and 9 single bonds present.(iii) Organic compounds of carbon and hydrogen containing one or more triple bonds are called alkynes. Their general formula is CnH2n-2.

Question 4

Question 10(a) Mention one function each of the following organs in human male reproductive system :TestisScrotumVas deferensProstate gland(b) Name the type of germ cell whichis motilestores food.

Accepted Answer

(a) Functions of given organs in human male reproductive system:Testis — It produces and stores sperms (male gamete).Scrotum — It holds the testis outside the body and maintains the temperature of testes at 2 to 3°C less than body temperature for the maturation of sperms.Vas deferens — Transports the sperm from epididymis to ejaculatory duct.Prostate gland — It pours an alkaline secretion into the semen as it passes through the urethra. It neutralises acid in female's vagina.(b) Type of germ cell which:is motile — Spermstores food — Ovum

Question 5

Question 11(a) Three resistors R1, R2 and R3 are connected in parallel and the combination is connected to a battery, an ammeter, a voltmeter and a key. Draw suitable circuit diagram to show the arrangement of these circuit components along with the direction of current flowing.(b) Calculate the equivalent resistance of the following network :

Accepted Answer

(a) Circuit diagram showing the arrangement:(b) We can see from figure that resistances R2 and R3 each of 10 Ω are connected in parallel. So, the equivalent resistance Rp is:1Rp=1R2+R3=110+110⇒1Rp=210⇒1Rp=15⇒Rp=5Ω\dfrac{1}{R_p} = \dfrac{1}{R_2 + R_3 } = \dfrac{1}{10} + \dfrac{1}{10} \[0.5em] \Rightarrow \dfrac{1}{R_p} = \dfrac{2}{10} \[0.5em] \Rightarrow \dfrac{1}{R_p} = \dfrac{1}{5} \[0.5em] \Rightarrow R_p = 5 ΩRp​1​=R2​+R3​1​=101​+101​⇒Rp​1​=102​⇒Rp​1​=51​⇒Rp​=5ΩNow, R1, Rp and R4 (each of 5 Ω ) are connected in series∴ Requi = 5 + 5 + 5 = 15 ΩSo, equivalent resistance of the circuit = 15 Ω.

Question 6

Question 12(a)(i) Define Electric Power and write its SI unit.(ii) Two bulbs rated 100 W; 220 V and 60 W; 220 V are connected in parallel to an electric mains of 220 V. Find the current drawn by the bulbs from the mains.

Accepted Answer

(i) Electric power is the rate at which electric energy is dissipated or consumed in an electric circuit.The SI unit of electric power is watt (W).(ii) Given,Voltage across the circuit = 220 VPower of first bulb (B1) be (P1) = 100 WPower of second bulb (B2) be P2 = 60 WP = V2R\dfrac{\text{V}^2}{\text{R}}RV2​orR = V2P\dfrac{\text{V}^2}{\text{P}}PV2​Resistance across B1 :Substituting in formula we get,R1 = 2202100\dfrac{\text{220}^2}{100}1002202​ = 484 ΩI = VR\dfrac{\text{V}}{\text{R}}RV​Substituting in formula we get,I1 = 220484\dfrac{220 }{484}484220​ = 0.454 AResistance across B2 :Substituting in formula above we get,R2 = 220260\dfrac{\text{220}^2}{60}602202​ = 806.6 ΩandI2 = 220806.6\dfrac{220}{806.6}806.6220​ = 0.272 ANow as they are connected in parallel, so the equivalent resistance is given by,1Rp=1R1+R2=1484+1806.6⇒1Rp=806.6+484484×806.6⇒1Rp=1290.6390394.4⇒1Rp=15⇒Rp=390394.41290.6=302.5Ω\dfrac{1}{R_p} = \dfrac{1}{R_1 + R_2 } = \dfrac{1}{484} + \dfrac{1}{806.6} \[1em] \Rightarrow \dfrac{1}{R_p} = \dfrac{806.6 + 484}{484 \times 806.6} \[1em] \Rightarrow \dfrac{1}{R_p} = \dfrac{1290.6}{390394.4} \[1em] \Rightarrow \dfrac{1}{R_p} = \dfrac{1}{5} \[1em] \Rightarrow R_p = \dfrac{390394.4}{1290.6} = 302.5 ΩRp​1​=R1​+R2​1​=4841​+806.61​⇒Rp​1​=484×806.6806.6+484​⇒Rp​1​=390394.41290.6​⇒Rp​1​=51​⇒Rp​=1290.6390394.4​=302.5ΩSo, equivalent resistance = 302.5 ΩAnd current through mains isI = 220302.5\dfrac{220}{302.5}302.5220​ = 0.727 AHence, current drawn by the bulbs from the mains = 0.727 A

Question 7

Question 12(b)(i) State Joule's law of heating. Express it mathematically when an appliance of resistance R is connected to a source of voltage V and the current I flows through the appliance for a time t.(ii) A 5 Ω resistor is connected across a battery of 6 volts. Calculate the energy that dissipates as heat in 10 s.

Accepted Answer

(i) Joules law of heating states that the heat dissipated across a resistor is directly proportional tothe square of the current flowing through itresistance of the conductorduration of flow of currenti.e., H = I2Rt(ii) Given,Resistance (R) = 5 ΩVoltage (V) = 6 VTime (t) = 10 sFrom ohm's law :V = IR6 = I x 5I = 65\dfrac{6}{5}56​ = 1.2 AEnergy dissipated (H) = I2RtSubstituting we get,H = 1.2 x 1.2 x 5 x 10 = 72 JHence, energy dissipated = 72 J.

Question 8

Question 13(a) Name the group of organisms which form in the first trophic level of all food chains. Why are they called so ?(b) Why are the human beings most adversely affected by bio-magnification ?(c) State one ill-effect of the absence of decomposers from a natural ecosystem.

Accepted Answer

(a) The group of organisms which form the first trophic level of all food chains are producers. They are called so because they are the only one to change the light energy of sun to chemical energy of food. The same energy goes to other trophic levels in food chains(b) Bio-magnification refers to progressive accumulation of chemicals at each trophic level. Human beings are most adversely affected by bio-magnification because they are at the top of any food chain. Therefore, the maximum concentration of these chemicals get accumulated in human bodies.(c) Without decomposers, the organic matter would not be efficiently broken down and recycled into essential nutrients, leading to the accumulation of dead organic matter in the ecosystem. This will disrupt the natural recycling of nutrients, negatively impacting soil fertility, promoting disease, and hindering the overall health and functioning of the ecosystem.

Question 9

Question 14The mechanism by which the sex of an individual is determined is called sex-determination. In human beings, sex of a newborn is genetically determined, whereas in some others it is not. There are 46 (23 pairs) chromosomes in human beings. Out of these, 44 (22 pairs) control the body characters and 2 (one pair) are known as sex chromosomes. The sex chromosomes are of two types X chromosome and Y chromosome. At the time of fertilisation, depending upon which type of male gamete fuses with the female gamete, the sex of the newborn child is decided.(a) Why is a pair of sex chromosomes in human beings called a mismatched pair in terms of type and size ?(b) Out of male or female, which of them has a perfect pair of sex chromosomes ? In case of a perfect pair, will the gametes produced be of the same kind or of a different kind ?(c) (i) Name two animals whose sex is not genetically determined. Explain the process of their sex determination.OR(ii) With the help of a flowchart only, show how sex is genetically determined in human beings.

Accepted Answer

(a) A pair of sex chromosomes in human beings is called a mismatched pair in terms of type and size because in males one chromosome is a normal-sized X while the other is a short one called Y. Such a pair of chromosome is known as heteromorphic.(b) Female has a perfect pair of sex chromosomes. Since all chromosomes are alike, the gametes produced are of same kind.(c) (i) The two animals whose sex is not genetically determined are Snail and Green Sea Turtle.Green Sea Turtle — Green Sea Turtle exhibits temperature-dependent sex determination. Temperature at which the eggs are incubated determines the sex of the offsprings. Cooler temperatures (around 29°C) result in the development of male hatchlings, while warmer temperatures (around 33°C) lead to the development of female hatchlings.Snail — In snails, individuals can change sex, indicating that sex is not genetically determined. The snail is born as a male but eventually changes into a female. Snails use physical contact with other snails to guide sex change.ORBelow flowchart shows genetic sex determination in human beings:

Question 10

Question 15A student fixes a sheet of white paper on a drawing board using some adhesive materials. She places a bar magnet in the centre of it and sprinkles some iron filings uniformly around the bar magnet using a salt-sprinkler. On tapping the board gently, she observes that the iron filings have arranged themselves in a particular pattern.(a) Draw a diagram to show this pattern of iron filings.(b) Draw the magnetic field lines of a bar magnet showing the poles of the bar magnet as well as the direction of the magnetic field lines.(c) (i) How is the direction of magnetic field at a point determined using the field lines ? Why do two magnetic field lines not cross each other ?OR(ii) How are the magnetic field lines of a bar magnet drawn using a small compass needle ? Draw one magnetic field line each on both sides of the magnet.

Accepted Answer

(a) Below diagram shows the pattern of iron filings:(b) The magnetic field lines of a bar magnet and its poles are shown below:(c) (i) The direction of the magnetic field lines at a place can be determined by using a compass needle.Two magnetic field lines never intersect each other. If they would intersect, this would mean that there are two directions of the field at the specific point which is not possible.OR(ii) Magnetic field lines can be mapped out using a small compass.We will mark the position of two ends of the needle of the compass.Now we will move the needle to a new position such that its south pole occupies the position previously occupied by its north pole.In this way, we will proceed step by step till we reach the south pole of the magnet as shown in Fig.Now we will join the points marked on the paper by a smooth curve. This curve represents a field line.We will repeat the above procedure, and get the magnetic field lines around the magnet.

Solved 2022 Term 2 Question Paper CBSE Class 10 Science

Section A (Very Short Answer Questions 2 Marks Each)

Section B (Short Answer Questions 3 Marks Each)

Section C (Source/Case Based Questions 4 Marks Each)