HBSE Class 10th Science Solved Question Paper 2019

HBSE Class 10th Science Solved Question Paper 2019

HBSE Class 10 Science Previous Year Question Paper with Answer. HBSE Board Solved Question Paper Class 10 Science 2019. HBSE 10th Question Paper Download 2019. HBSE Class 10 Science Paper Solution 2019. Haryana Board Class 10th ScienceQuestion Paper 2019 Pdf Download with Answer.

SET-A

Q1. The blue colour of sky is due to :

(A) Reflection of light

(B) Scattering of light

(D) Refraction of light

Ans. (B) Scattering of light

Q2. Which of the following is not an example of a biomass energy source ?

(A) Wood

(B) Gobar gas

(D) Coal

Ans. (C) Nuclear energy

Q3. What type/nature of image is formed by the eye lens at retina ?

Ans. Human eye lens are convex in nature and form real and inverted images.

Q4. On what factors the resistance of conductor depends ?

Ans. Resistance of conductor depends on-

(i) Length of the wire

(ii) Area of cross-section of the wire

(iii) Nature of material of the wire.

Q5. What are the disadvantages of fossil fuel ? Explain in brief.

Ans. The burning of coal and petroleum produces a lot of pollutants, causing air pollution. Fossil fuels release oxides of carbon, nitrogen, sulphur, etc., that cause acid rain, affecting soil fertility and potable water. The burning of fossil fuels produce gases such as carbon dioxide that causes global warming.

Q6. How can three resistors of resistance 2 Ω, 3 Ω, and 6 Ω be connected to give a total resistance of 4 Ω ?

Ans. We can get a total resistance of 4Ω by connecting the R1=2Ω resistance in series with the parallel combination of R2=3Ω and R3=6Ω. When Resistance in parallel then

1/RP = 1/R2 + 1/R3 = 1/3 + 1/6 = 1/2

R = 2Ω

Resistance in series :

RS = R + R1 = 2Ω + 2Ω = 4Ω

Q7. What are the advantages of water stored in the ground ?

Ans. advantages of water stored in the ground-

(i) It does not evaporate

(ii) It recharges wells near the area

(iii) It provides moisture to the vegetation

(iv) It does not provide breeding grounds for mosquitos , like stagnant water in lakes and ponds

(v) It is relatively protected from contamination by animal and human waste.

Q8.(a) Light enters from air to glass having refractive index 1.50. What is the speed of light in glass ? The speed of light in vacuum is 3 × 10⁸ ms-¹.

Ans. Refractive index μ = 1.50, Speed of light c=3×10⁸ m/s, we know that μ = c/v

v = c/μ = 3×10⁸/1.50 = 2 × 10⁸ m/s

Hence, the speed of light in glass is 2×10⁸ m/s.

(b) An object is situated at a position in between the main focus (F) and 2 F of a Convex lens. Draw the ray diagram showing the position, size and nature of image formed.

Ans. A ray from infinity i.e. parallel to principal axis of pole falls on lens and passes through focus of lens after refraction. Another ray falls on the pole of lens & passes without any deviation. Image is formed where two refracted rays intersect each other.

Position of image – image is beyond 2F

Size of image – more than size of object

Nature of image – image is inverted

Q9. Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes ?

Ans. Principle– In an electric generator, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity. It is working on the principle of electromagnetic induction.

Working– When the axle attached to the two rings is rotated such that the arm AB moves up (and the arm CD moves down) in the magnetic field produced by the permanent magnet. Let us say the coil ABCD is rotated clockwise in the arrangement. By applying Fleming’s right hand rule, the induced currents are set up in these arms along the directions AB and CD. Thus an induced current flows in the direction ABCD. If there are larger number of turns in the coil, the current generated in each turn adds up to give a large current through the coil. This means that the current in the external circuit flows from B2 to B1. After half a rotation, arm CD starts moving up and AB moving down. As a result, the directions of the induced currents in both the arms changes, giving rise to the net induced current in the direction DCBA. The current in the external circuit now flows from B1 to B2. Thus after every half rotation the polarity of the current in the respective arms changes. There are two brushes and in the electric generator, one brush is at all times in contact with the arm moving up in the field, while the other is in contact with the arm moving down. Because of these Brushes unidirectional current is produced.

Function of brushes is to transfer the current from coil to load connected in the circuit of the electric generator.

(a) What is the Fleming’s Left-Hand Rule ? Explain.

Ans. When a current-carrying conductor is placed in an external magnetic field, the conductor experiences a force perpendicular to both the field and to the direction of the current flow. It was invented by John Ambrose Fleming.

(b) What do you mean by electromagnetic induction ? Explain the use of Fleming’s right-hand rule in finding the direction of current induced in the conductor.

Ans. Electromagnetic Induction (EMI) is a current produced because of voltage production (electromotive force) due to a changing magnetic field. This either happens when a conductor is placed in a moving magnetic field (when using an AC power source) or when a conductor is constantly moving in a stationary magnetic field.

Fleming’s Right Hand Rule states that if we arrange our thumb, forefinger and middle finger of the right-hand perpendicular to each other, then the thumb points towards the direction of the motion of the conductor relative to the magnetic field, the forefinger points towards the direction of the magnetic field and the middle finger points towards the direction of the induced current.

Q10. Which reactant is Oxidized in the following chemical reaction ?

CuO + H2 → Cu + H2O

Ans. Hydrogen is oxidized and Copper is reduced.

Q11. You have three solutions A, B and C whose pH value is 4, 7 and 10 respectively. Out of above solutions, which solution is acidic ?

Ans. Solution A is acidic (pH=4). We know that If pH<7 then Acidic, If pH=7 then Neutral, If pH>7 then Basic.

Q12. Element M forms a Chloride with formula MCl. Element M would be most likely in the same group of Periodic table as :

(A) Si

(B) Al

(D) Mg

Ans. (C) Na

Q13. What do you mean by displacement reactions ? Give one example (Chemical equation).

Ans. The reaction in which one element displaces or remover another element from its solution is called displacement reaction.

eg. Zn + CuSO4 → ZnSO4 + Cu

Q14. What is chemical formula of baking soda ? Give chemical equation used in its preparation.

Ans. Chemical formula of baking soda is NaHCO3 .

NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3

Q15. In modern periodic table how does atomic size vary on moving down top to bottom in a group ? Write its reason.

Ans. The atomic size increases down the group. This is because new shells are added as we go down the group. This increase the distance between outermost electrons and the nucleus. Hence atomic size increases in spite of increase in nuclear charge.

Q16.(i) What happens when metals are burnt in air ? Give one example.

Ans. Almost most of metals on burning combine with oxygen to form metal oxides.

eg. 2Cu + O2 → 2CuO

(ii) Write short note on electrolytic refining of metals.

Ans. The impure metal is made the anode and a thin strip of pure metal is made the Cathode. A solution of metal salt is used as an electrolyte. On passing the current through the electrolyte, the pure metal from anode dissolves into the electrolyte. An equivalent amount of pure metal from the electrolyte is deposited on Cathode.

Q17.(i) Write the names of following compounds :

Ans.

(a) Chloromethane

(b) Propanoic acid

(ii) How ethanoic acid react with the following ? Give chemical equation :

(a) Na2CO3

(b) NaOH

Ans.

(a) 2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2

(b) CH3COOH + NaOH → CH3COONa + H2O

Explain the following Properties of Carbon compounds with example :

(i) Oxidation reaction

(ii) Addition reaction

(iii) Substitution reaction

Ans.

(i) Carbon compounds can be easily oxidized by combustion (Oxygen is added).

eg. CH4 + 2O2 → CO2 + 2H2O + Heat & Light

Ethylalcohol can be oxidized to ethanoic acid by oxidizing agent.

eg. CH3–CH2OH + Alkaline KMnO4 + Heat → CH3COOH

(ii) Unsaturated hydrocarbons add hydrogen in presence of catalyst such as Pd or Ni to give saturated hydrocarbons.

(iii) In saturated hydrocarbons, in presence of sunlight chlorine is added in a very fast reaction. Chlorine replaces the H atoms of hydrocarbons one by one.

eg. CH4 + Cl2 + Sunlight → CH3Cl + HCl

Q18. Which of the following is group of only biodegradable substances ?

(A) Plastic, Leather, Wood

(B) Grass, Plastic, Banana Peel

(D) Leather, Glass, Banana Peel

Ans. (C) Wood, Grass, Banana Peel

Q19. The growth of pollen tube towards ovule is an example of :

(A) Geotropism

(B) Chemotropism

(D) Hydrotropism

Ans. (B) Chemotropism

Q20. Name the solar radiation from which the surface of earth is shielded by ozone layer.

Ans. UV rays (Ultra violet radiations)

Q21. What is the name of the process of formation of new individual in Amoeba ?

Ans. Binary fission

Q22. What is the name of the gland secreting adrenaline hormone ?

Ans. Adrenal gland

Q23. What is function of testis in man ?

Ans. Testis or testicles are sperm-producing organs occurring in pairs in humans. It helps in maintaining the health of the male reproductive system. The testes lie outside the body and are maintained at a temperature about two degrees Centigrade lower than the body’s core temperature.

Q24. What are unisexual and bisexual flowers ? Give examples.

Ans. Unisexual Flowers– The flowers in which either the male or the female reproducative organs are present only, are called unisexual flowers. They are called incomplete flowers. They undergo cross-pollination in order to reproduce. eg. Papaya, Watermelon, Corn, etc.

Bisexual Flowers– The flowers in which both the male and female reproductive organs are present, are known as complete or bisexual flowers. They are capable of self-pollination. eg. Mustard, rose, lily, hibiscus, etc.

Q25. What is the function of medulla and cerebellum in human brain ?

Ans. Function of Medulla– Medulla directly controls many involuntary responses like sneezing and blinking of eye. It controls our overall major motor functions, or body movement. It carries out blood vessel dilation to increase or decrease oxygen flow and respond to heart function. Other functions include digestion, swallowing and vomiting to get rid of bacteria or pathogens that could harm us.

Function of Cerebellum– The cerebellum receives information from the sensory systems, the spinal cord and other parts of the brain and regulates the motor movements. It controls the voluntary movements such as posture, balance, coordination, and speech to maintain a smooth and balanced muscular activity.

Q26. Rounded seeds (dominant trait) were crossed with wrinkled seeds (recessive trait).

(i) What type of seeds will be produced in F1 generation ? Explain with diagram.

Ans. Rounded Seeds, As RR (rounded) and rr(wrinkled) are crossed the seeds would be Rr, Rr, Rr, Rr which all would be rounded.

(ii) By self-pollination in F1 seeds, what percentage of seeds will be rounded shape in F2 generation ? Explain with diagram.

Ans. 75%, After self pollination in F1 hybrid, the seeds would be RR, Rr, Rr, rr. 3/4 would be rounded so the percentage would come as 75%.

Q27. Draw a well labelled diagram of excretory system and explain the process of urine formation in human being.

Ans. Labelled Diagram of Human Excretory System–

Process of Urine formation in Human Being–

Kidneys are the primary structure for the elimination of waste products. There are millions of functional units in the pair of kidneys. These functional units are named nephrons. The kidney filters unwanted substances from blood and excretes them through the production of urine. The urine is then transported to the central cavity known as the pelvis. A pair of the duct (ureters) collects the urine from the kidney. The ureters of both the kidneys end in the urinary bladder via a tube known as the urethra. In males, the urethral opening is through the pelvis and near the vagina in females. There are three steps in urine formation i.e Glomerular filtration, reabsorption, and secretion. These processes ensure that only waste and excess water gets removed from the body.

Describe excretion in plants.

Ans. Excretion in Plants– Removal of the waste and toxic products from the body is called as excretion. All the living organisms excrete their wastes. Like animals, plants do not have a special organ for excretion. They excrete through their vegetative parts only. Oxygen is a by-product of photosynthesis, which is excreted from the leaves of plants. Excess water is excreted as water vapour by the process of transpiration. Plants store there some of the excretory products in leaves and get rid of that by losing them. Some of the plants store their excretory product as resins, gums, latex, oils etc in stems, leaves and bark. Eventually, plants shed off their parts and thus excretion occurs. Plant produces secondary metabolites that are not used by plants but used by animals such as alkaloids. Alkaloids are nitrogenous compounds stored in different parts of the plant. It is used as a medicine, sedatives, and insecticides. Excretion in aquatic plants takes place through diffusion.

SET-B

Q1. Colour of the sun at sunrise is red due to :

(A) Scattering

(B) Dispersion

(D) Reflection

Ans. (A) Scattering

Q2. Which of the following is not an example of a bio-mass energy source ?

(A) Wood

(B) Gobar gas

(D) Nuclear energy

Ans. (D) Nuclear energy

Q3. What is the function of iris ?

Ans. The function of the iris in the eye is to control the amount of light that reaches the retina. It does this by changing the size of the pupil, the transparent window that allows light into the eye’s interior.

Q4. On what factors does the resistance of conductor depends ?

Ans. Resistance of conductor depends on-

(i) Length of the wire

(ii) Area of cross-section of the wire

(iii) Nature of material of the wire.

Q5. What are the properties of a good source of energy ?

Ans. It should provide large amount of energy per unit mass (high calorific value). It should be easily accessible. It should provide energy for maximum period of time and it should be renewable. It should be sustainable and safe (pollution free) for the environment.

Q6. An electric motor takes 5.0 A from 220 V line. Determine the power of the motor and energy consumed in 2 hour.

Ans. Power of the motor = V × I = 220 × 5 = 1100 watt or 1.1 kW

Energy = power × time = 1.1 kW × 2 h = 2.2 kWh

Q7. You must have come across the three R’s to save the environment :

Reduce, Recycle and Reuse. Explain Reuse in detail.

Ans. Reuse– This is even better than recycling because it save the energy which is spent at recycling a products no energy is required during reuse. We should use the same things again. For example – envelopes can be used by reversing them.

Q8.(a) An object is placed at the centre of curvature (C) of a concave mirror. Draw the ray diagram to depict the position, size and nature of image formed.

Ans.

Nature of image – A real, inverted image

Position of image – image formed is at C

Size of image – equal to the object AB

(b) Find the focal length of a lens of power -2.0 D. What type of lens in this ?

Ans. Power = 1/focal length (in meter)

F = 1/P = 1/(-2) = – 0.5 m = – 50 cm

The lens given is a Concave Lens as it has a negative value for power.

Q9. Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes ?

Ans. Principle– In an electric generator, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity. It is working on the principle of electromagnetic induction.

There are two brushes and in the electric generator, one brush is at all times in contact with the arm moving up in the field, while the other is in contact with the arm moving down. Because of these Brushes unidirectional current is produced. Function of brushes is to transfer the current from coil to load connected in the circuit of the electric generator.

(a) What is a solenoid ? Draw the magnetic lines of force around the current carrying solenoid. Write the use of solenoid.

Ans. Solenoid– A solenoid is a coil which is made of an insulated wire wound in the form of a cylinder usually made of solid iron, solid steel, or powdered iron which produces magnetic field when electrical phenomenon is suffered through it and behaves as a magnet.

Use of Solenoid– A solenoid is used to control a valve electrically, for example, the solenoid core is used to apply mechanical force to the valve. Solenoid can also used in particular types of door locking systems, which use an electromagnet and offer a very secure closure. The solenoid is used in many different appliances and products like computer printers, fuel injection gear used on cars and in various industrial settings. The main advantage of the solenoid is, whenever an electricity is applied, the reaction of the solenoid is immediate.

(b) What is the Fleming’s Right-Hand Rule ? Explain.

Ans. Fleming’s Right Hand Rule states that if we arrange our thumb, forefinger and middle finger of the right-hand perpendicular to each other, then the thumb points towards the direction of the motion of the conductor relative to the magnetic field, the forefinger points towards the direction of the magnetic field and the middle finger points towards the direction of the induced current.

Q10. Which reactant is Reduced in the following chemical reaction ?

CuO + H2 → Cu + H2O

Ans. Hydrogen is oxidized and Copper is reduced.

Q11. You have three solutions A, B and C whose pH value is 3, 7 and 9 respectively. Out of above solutions, which solution is acidic ?

Ans. Solution A is acidic (pH=3). We know that If pH<7 then Acidic, If pH=7 then Neutral, If pH>7 then Basic.

Q12. Element M forms a Chloride with formula MCl2. Element M would be most likely in the same group of Periodic table as :

(A) Si

(B) Al

(D) Mg

Ans. (D) Mg

Q13. What do you mean by double displacement reactions ? Give one example (Chemical equation).

Ans. Reactions in which there is an exchange of ions between the reactants are called double- displacement reactions.

eg. Na2SO4 + BaCl2 → BaSO4 + NaCl

Q14. What is chemical formula of bleaching powder ? Give chemical equation used in its preparation.

Ans. Chemical Formula of Bleaching powder is CaOCl2 .

Ca(OH)2 + Cl2 → CaOCl2 + H2

Q15. In modern periodic table, how does the metallic character vary in a period on moving from left to right in a period ? Write its reason.

Ans. The metallic character decreases across a period. Metals are electropositive i.e. they tend to loose electrons. The effective nuclear charge acting on valance shell electron increases across a period, hence tendency to loose electron and metallic character decreases.

Q16.(i) What happens when metals react with acids ? Give one example.

Ans. Metals react with acids to give a salt and hydrogen gas.

eg. Zn + 2dil.HCl → ZnCl2 + H2

(ii) Explain the reactivity series with example.

Ans. The reactivity series is a list of metals arranged in order of their reactivities.

Most Reactive – K, Na, Ca

Medium Reactive – Zn, Fe, Pb

Least Reactive – Cu, Ag, Au

Q17. (i) Write the names of following compounds :

Ans.

(a) Ethanoic acid

(b) Chloroethane

(ii) What is homologous series ? Explain with example.

Ans. A series of organic compounds in which the some functional group substitutes for hydrogen in a carbon chain is called homologous series.

eg. alkane homologous series (CH4 -Methane, C2H6 -Ethane, C3H8 -Propane, C4H10 -Butane …..)

Properties– Mol. mass of two consecutive members differ by 140. Two members differ by 2CH unit. Chemical properties remains same. Physical properties show regular variation.

Explain the mechanism of cleaning action of soap.

Ans. Most dist is oily in nature and oil does not dissolve in water. The molecules of soap are sodium or potassium salt of long chain carboxylic acid. The ionic end of soap dissolves in water while the carbon chain dissolves in oil. The soap molecules form structures called miscelle. In miscelle one part of molecule is towards oil droplet while the ionic end faces outside. This forms an emulsion in water. The soap miscelle thus helps in dissolving the dirt in water and we can wash our clothes clean.

Formation of miscelles

Q18. Which of the following is a group of only non-biodegradable substances ?

(A) Aluminium, Plastic, Leaves

(B) Plastic, Grass, Wood

(D) Leaves, Grass, Plastic

Ans. (C) Aluminium Can, Plastic, Glass Bottle

Q19. Wilting of leaves in plants is due to effect of which of the following ?

(A) Cytokinin

(B) Auxin

(D) Abscissic Acid

Ans. (D) Abscissic Acid

Q20. Which synthetic chemical is responsible for depletion of ozone layer ?

Ans. CFCs (Chloro Fluoro Carbon)

Q21. What is Regeneration ?

Ans. Regeneration is one of the processes in which if an organism is cut into several pieces, each of its parts regrows to the original state. This process is carried out by specialized cells called stem cells. It takes place in organisms that have a very simple structure with very few specialized cells. eg. Planaria or Hydra

Q22. Iodine is necessary for the synthesis of which hormone ?

Ans. Thyroxine

Q23. What is the function of ovary in human beings ?

Ans. It produces ova (egg) every month in a female during menstrual cycle. It produces female sex hormones, i.e. estrogen and progesterone, which play an important role in the development of secondary sexual characteristics in female and in pregnancy.

Q24. What is vegetative propagation ? How is it useful ?

Ans. Vegetative propagation is often used when the crop plants either do not produce seeds or when the seeds produced are not viable or are of long dormancy. The method relies on the use of pieces of vegetative plant parts such as stems, leaves, or roots to perpetuate the parent plants.

Q25. What is reflex arc ? What is the function of sensory neuron in reflex arc ?

Ans. A reflex arc is a neural pathway that controls a reflex. In vertebrates, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This allows for faster reflex actions to occur by activating spinal motor neurons without the delay of routing signals through the brain. The basic function of sensory neuron is to carry the impulse from sensory organ to the central nervous system.

Q26. As per Mendel’s Law, describe the independent assortment of two separate traits (rounded and green seeds) with (wrinkled and yellow seeds) along with diagram.

Ans. According to Mendel’s law of independent assortment, during the inheritance of two or more characters, the assortment of individual traits takes place independently during gamete formation. Thus each allele of a pair segregates independently and each gamete formed contains one allele of that trait. This law is inapplicable for linked genes. Mendel performed the dihybrid cross from which he showed that the traits are inherited independently.

The genotype of the F1 plants is RrYy. These plants were self-crossed by Mendel. In his dihybrid cross the F2 plants were obtained in the phenotypic ratio 9 (round yellow):3 (round green) :3 (wrinkled yellow):1 (wrinkled green) as shown in the Punnett square. The seed colour is inherited independently of the seed shape. Thus round green seeds, as well as yellow wrinkled seeds both were formed along with round yellow seeds and green wrinkled seeds.

Q27.(i) By which part of plant translocation of food takes place ? Where is the food translocated ?

Ans. Part of plant responsible for translocation Phloem. Translocation sites – Root, Fruit, Seeds.

(ii) Explain the process of translocation of food in plants.

Ans. Translocation is the process by which plants deliver minerals, plant growth hormones, water, and organic substance over long distances throughout the plants (from leaves to other parts). Leaves produced the carbohydrates (sugar) through the process of photosynthesis, but other parts also required the sugar for their function. Due to this reason, the nutrients are translocated from sources (the area where carbohydrates are formed i.e., mature leaves) to the sink (the area where carbohydrates are needed). Examples of the sink are stem, root, fruits, developing seeds, etc. It occurs in the series of the cells called the phloem pathway. The phloem is present in the vascular bundle and is arranged in long, continuous strands which extend through the root and stem and reach to leaves as veins. It helps in the transportation of food materials. These food nutrients are translocated in the form of solutes in a solution known as phloem sap. Food nutrients include amino acids, sugar, etc. These nutrients are utilized by the various cells to support their requirements for life and they are also stored for future use. These nutrients are specially delivered to developing seeds and fruits. Apart from the phloem, the vascular bundle also consists of xylem. This is responsible for the transportation of water and dissolved minerals from the root to shoot.

(i) How does transport of oxygen and carbon dioxide takes place in human beings ? Describe in detail.

Ans. The oxygen is inhaled through nostrils filling up the lungs and get diffused within the blood through alveoli, the four molecules of which binds with the hemoglobin and are transported within the blood. Not entire carbon dioxide is exhaled, few amounts of carbon dioxide are transported in the blood as the solubility of carbon dioxide in water is greater than oxygen. It forms compounds required for activities in reaction with water. Various minute alveolar sacs are present at the end of the tubes of the bronchiole. When the lungs are filled with air, their surface area increases as the surface area of millions of alveoli sacs increases. Enough oxygen is inhaled due to the increased surface area sufficient to carry out the activities.

(ii) Why terrestrial organisms have advantage over aquatic organisms with regard to obtaining oxygen for respiration ?

Ans. Terrestrial organisms breathe by using atmospheric oxygen whereas aquatic organism takes oxygen dissolved in water. A terrestrial animal has over an aquatic animal with regard to obtaining oxygen for respiration. It’s because the air in the atmosphere contains the maximum amount of oxygen. Oxygen level is high in the atmosphere when compared to oxygen in the water. Aquatic animals have only dissolved oxygen in the water, which is in minimal amount. Hence, the terrestrial animal has over an aquatic animal with regard to obtaining oxygen for respiration.

SET-C

Q1. The human eye forms the image of an object at its :

(A) Cornea

(B) Retina

(D) Pupil

Ans. (B) Retina

Q2. Which of the following gas is found maximum in biogas ?

(A) Methane

(B) Carbon dioxide

(D) Hydrogen

Ans. (A) Methane

Q3. Which phenomenon of light is responsible for twinkling of stars ?

Ans. Atmospheric Refraction

Q4. Why are coils of an electric toaster and electric irons made of an alloy rather than a pure metal ?

Ans. Because the resistivity of an alloy is higher than the pure metal.

Q5. What are the disadvantages of fossil fuel ? Explain in brief.

Ans. Fossil fuel make Air pollution. The oxides of carbon, nitrogen, and sulphur that are released on burning fossil fuels are acidic oxides. These lead to acid rain which affects our water and soil resources. Global warming- the greenhouse effect of gases like carbon dioxide. The fossil fuels are non-renewable sources of energy.

Q6. Show how you would connect three resistors, each of resistance 6 Ω. So that the combination has a resistance of 4 Ω.

Ans. Here two resistors are joined in series and these two are joined in parallel with third one.

Rs = 6Ω + 6Ω = 12Ω (two resistors are in series) and now Rs is joined in parallel with 6Ω. so, effective resistance, R = 12 × 6/(12 + 6) = 72/18 = 4Ω

Q7. How the constructions of large dams cause social and environmental problems ?

Ans. Social Problems– Vast area of land gets submerged under water so, many people become homeless. It also leads to unequal distribution of water. People close to the source will get enough water for agriculture whereas those far from the source cannot get sufficient water.

Environment Problems– Large-scale deforestation, loss of flora and fauna of that particular area, displacement of large number of people living in that area etc.

Q8.(a) What is the power of a lens ? Define one Diopter (1D) power of a lens.

Ans. Power of a lens is its ability to converge or diverge the rays of light falling on it. One dioptre is the power of the lens whose focal length is 1m. Power = 1/focal length = 1 D

(b) An object is placed between the main focus (F) and the optical centre (O) of a convex lens. Draw a ray diagram showing the position, size and nature of the image formed.

Ans.

Position of image – image is in same side of object & lens

Size of image – more than size of object

Nature of image – image formed is erect, virtual and magnified .

Q9. Draw labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor ?

Ans. Principle– An electric motor is a rotating device that converts electrical energy to mechanical energy working.

Working– Current in the coil ABCD enters from the source battery through conducting brush X and flow back to the battery through brush Y. Notice that the current in the arm AB of the coil flows from A to B. In arm CD it flows from C to D that is opposite to the direction of current through arm AB on applying Fleming’s left hand rule for the direction of force on a current-carrying conductor in a magnetic field. We find that the force acting on arm AB pushes it downwards while the force acting on arm CD pushes it upwards. Thus the coil and the Axle O, mounted free to turn about an axis, rotate anti-clockwise at half rotation. Q makes contact with the brush X and P with brush Y. Therefore the current in the coil gets reversed and flows along the path DCBA. The reversal of current also reverses the direction of force acting on the two arms AB and CD. Thus the arm AB of the coil that was earlier pushed down, is now pushed up and the arm CD previously pushed up is pushed down. There is a continuous rotation of the coil and to the axle.

Split rings in electric motors acts as a commutator.

(a) What do you mean by earthing ? Why should electrical appliances be earthed ?

Ans. Earthing is the process of transferring the immediate discharge of electricity directly to the earth plate, by means of low resistance electrical cables or wires. Earthing is a proper connection of exposed metal parts to electric circuit from ground.

To avoid the risk of electric shock metal body of an electric appliances is earthed. This is used as safety measure especially for those appliance that have metallic body for example electric iron, toaster etc. The metallic body is connected to low resistance conducting path for current. Thus, it ensures that any leakage of current to the metallic body of appliance keep its potential to that of the earth and a user may not gets the severe electric electric shock.

(b) What is a solenoid ? Draw the magnetic field around a current carrying solenoid. Write down the use of a solenoid.

Q10. Which reactant is Oxidized in the following chemical reaction ?

ZnO + C → Zn + CO

Ans. Carbon is oxidized (due to loss of electrons) and Zinc is reduced (due to gain in electron).

Q11. You have three solutions A, B and C whose pH value is 2, 7 and 11 respectively. Out of above solutions, which solution is neutral ?

Ans. Solution B is neutral (pH=7). We know that If pH<7 then Acidic, If pH=7 then Neutral, If pH>7 then Basic.

Q12. Element M forms a Chloride with formula MCl4. Element M would be most likely in the same group of Periodic table as :

(A) Si

(B) Al

(D) Mg

Ans. (A) Si

Q13. What do you mean by combination reactions ? Give one example (chemical equation).

Ans. The reactions in which a single product is formed from two or more reactants are known as combination reactions.

eg. CaO + H2O → Ca(OH)2

Q14. What is the chemical formula of washing soda ? Give chemical equation used in its preparation.

Ans. Chemical formula of Washing Soda is Na2CO3.10H2O .

2NaHCO3 + Heat → Na2CO3 + H2O + CO2

Na2CO3 + 10H2O → Na2CO3.10H2O

Q15. In modern periodic table, how does metallic character vary on moving down top to bottom in a group ? Write its reasons.

Ans. Metallic character increases down the group. Metals are electropositive i.e. they tend to loose electrons. Down the group the effective nuclear charge experienced by valance electrons is decreasing because the outermost electrons are farther away from nucleus. Hence these can be lost easily and metallic character increases down the group.

Q16.(i) What happens when metals react with water ? Give one example.

Ans. Metals react with water and produce a metal oxide and hydrogen gas.

eg. 2Na + 2H2O → 2NaOH + H2

(ii) What is thermit process ? Give chemical equation of this process.

Ans. The displacement reaction between iron (III) Oxide (Fe2O3) and Al is highly exothermic and the Fe is obtained in molten State. It is used to join railway tracks or cracked machine parts.

Fe2O3 + 2Al → 2Fe + Al2O3 + Heat

Q17. (i) Write the names of following compounds :

Ans.

(a) Propane

(b) Bromoethane

(ii) How ethanol reacts with the following ? Give chemical reactions.

(a) Acidified potassium dichromate

(b) Hot concentrated H2SO4

Ans.

(a) CH3CH2OH + Acidified K2Cr2O7 → CH3COOH (Ethanoic acid)

(b) CH3CH2OH + Hot Conc.H2SO4 → CH2=CH2 + H2O (Ethene)

Explain in detail the nomenclature of Carbon compounds.

Ans. Naming of a carbon compound can be done by the following method.

Identify the number of carbon atoms in the compound. A compound having three carbon atoms would have the name propane.

In case a functional group is present, it is indicated in the name of compound with either a prefix or suffix.

If the name of the functional group is to be given as a suffix, the name of the carbon chain is modified by deleting the final ‘e’ and adding a appropriate suffix e.g. a three carbon chain with an aldehyde group would be named in the following manner :

Propane + e- → Propan +al → Propanal

If the carbon chain is unsaturated, then the final ‘ane’ in the name of carbon chain is substituted by ‘ene’ or ‘yne’. eg. a four carbon chain with a triple bond would be called Butyne. If it has a double bond is would be called ‘Butene’.

Q18. The organisms which make organic compounds from inorganic substances using energy of sun and in the presence of chlorophyll are called :

(A) Decomposers

(B) Producers

(D) Carnivores

Ans. (B) Producers

Q19. ‘Salivation’ is a type of process :

(A) Voluntary

(B) involuntary

(D) Reflex Action and involuntary Both

Ans. (B) Involuntary

Q20. What percentage of solar energy captured by green plants is converted into food energy in a terrestrial ecosystem ?

Ans. 1%

Q21. Which organism divides into many daughter cells through multiple fission ?

Ans. Plasmodium

Q22. Name the hormone responsible for limiting the sugar level in blood in human beings.

Ans. insulin

Q23. Write those changes of puberty that are common to girls and boys.

Ans. Hair grow under armpits, in genital area between the thighs. Thinner hair appear on arms and legs. Skin become oily and develops pimples.

Q24. What is difference between pollination and fertilization ?

Ans. Pollination– Pollination is an external process. Pollination takes place before fertilization. Pollination occurs from anthers of stamens to stigma of the ovary. It is a physical process. Pollination agents are wind, water, birds, insects, and other animals. External factors are required. This process leads to fertilization. The pollen tube is not required. Pollination occurs only in flowering plants.

Fertilization– Fertilization can either be internal or external. Fertilization occurs after pollination. It is the fusion of female and male gametes. It is a genetic and biochemical process. Fertilization takes place by growing pollen tube which enters the ovule. External factors are not required. This process leads to the formation of seeds. Pollen tubes are formed for transferring male gametes into an egg cell. Fertilization is followed by almost in every living being present on the planet earth, including plants, animals, birds, insects, humans, etc.

Q25. Explain the process of response to touch in sensitive plant.

Ans. Leaves of the sensitive plant protect themselves from predators and environmental conditions by folding in response to touch. When the Mimosa pudica, commonly known as the sensitive plant, is touched by another organism, its leaves fold in upon themselves and its stems droop.

Q26. What are different ways in which individuals with a particular trait may increase in population ?

Ans. Natural Selection– If a trait is useful to the population, it will increase naturally. It may directly lead to the evolution of species populations by adaptations to fit their environment better. That particular trait may thus increase in the population.

Genetic Drift– If a population faces an accident such that the majority of its members get killed, the remaining members will pass on their traits to the subsequent generations. This leads to an increase of the trait in the population. This is the notion of genetic drift, which provides diversity without any adaptation.

Geographic isolation– Where a population of species gets separated by their respective group due to physical/natural barriers.

Mutation– Slight changes in the genetic information of the offspring during fertilization.

The trait is beneficial to the population: If a trait is beneficial to a population, it will increase naturally. Such green color in beetles is favorable as it helps them in camouflage against predators.

Q27. What part of plant transports water ? Explain the movement of water and minerals in plants.

Ans. Xylem is fundamental tissue for transportation of water. In plants, minerals and water are transported through the xylem cells from soil to the leaves. The xylem cells of the stem, roots, and leaves are interconnected forming a conducting channel reaching all plant parts.

Transport of water and materials is necessary for plants to maintain a regular supply of oxygen and nutrients to all the cells present in the body. Plants contain special tissues and organs for the transport of substances so that they can easily transport essential substances like food, oxygen, and water from one part of the body to another in a multicellular organism. Water and minerals are absorbed by the cells of the root hair. As water is absorbed by the root hairs from the soil, it is transported to various parts of the plants through the xylem tubes by the cohesion of water molecules to each other. Then, there is a steady movement of water from the root xylem to all the parts of the plant, through interconnected water conduction elements. Transpiration also helps in the movement of water. Due to transpiration, a continuous force is developed which pulls the water upward. this force or pull is also known as transpiration pull. The major minerals required for the growth of the plant are calcium, magnesium, phosphorus, potassium, sodium, chlorine, and sulphur. The transport of food from the leaves to the other parts of the plant occurs through the vascular tissue known as the phloem and the process is known as Translocation. The food (sugar molecules) made in leaves is loaded into the sieve tubes of phloem by using energy in the form of ATP. As a result, the osmotic pressure increases and water moves into the tissue and pushes the food to the plant parts having a low pressure. This process is helpful in moving the food materials according to the needs of the plant.

(i) What is difference between blood and lymph ?

Ans. Blood– Blood reddish coloured fluid. Blood is part of the circulatory system. Blood is involved in the circulation of nutrients, hormones, oxygen and carbon dioxide, wastes and other toxins. Blood contains plasma, RBCs, WBCs and platelets. Blood carries more oxygen and digested food. Blood helps to regulate the body temperature and water contents in our body.

Lymph– Lymph is colourless fluid. Lymph is Part of the lymphatic system. Lymph helps in body defence and is a part of the immune system. Lymph contains plasma and a lesser number of WBCs and platelets. Lymph carries less oxygen and digested food. Lymph can supply nutrients to our body and removes metabolic waste from tissues.

(ii) Explain the process of double circulation with the help of schematic representation of oxygen and carbon dioxide transport in human beings.

Ans. Double circulation is a process during which the blood passes two times the heart in one cycle. The heart is four chambered. The movement of blood in an organism is divided into two parts :

Systemic Circulation– involves the movement of oxygenated blood from the left ventricle of the heart to the aorta. It is then carried by blood through a network of arteries, arterioles, and capillaries to the tissues. From the tissues, the deoxygenated blood is collected by the venules, veins, and vena cava, and is emptied into the left auricle.

Pulmonary Circulation– involves the movement of deoxygenated blood from the right ventricle to the pulmonary artery, which then carries blood to the lungs for oxygenation. From the lungs, the oxygenated blood is carried by the pulmonary veins into the left atrium.

Hence in double circulation, blood has to pass alternately through the lungs and the tissues.

SET-D

Q1. The main reason behind the advanced sunrise and delayed sunset is ……………. of light.

(A) Reflection

(B) Refraction

(D) Scattering

Ans. (D) Scattering

Q2. Which of the following is not an example of bio-mass energy source ?

(A) Wood

(B) Gobar gas

(D) Coal

Ans. (C) Nuclear energy

Q3. The prism split the incident white light into a band of colours. Write these colours name in sequence.

Ans. Violet, Indigo, Blue, Green, Yellow, Orange, and Red

Q4. On what factors, the resistance of a conductor depends ?

Ans. Resistance of a conductor depends on-

(i) Length of the wire

(ii) Area of cross-section of the wire

(iii) Nature of material of the wire.

Q5. What are the properties of a good source of energy ?

Q6. How can three resistors of resistances 2 Ω, 3 Ω and 6 Ω be connected to give a total resistance of 1 Ω ?

Ans. We can obtain a total resistance of 1 Ω by connecting resistors of 2 Ω, 3 Ω and 6 Ω in parallel.

1/Rp = 1/R1 + 1/R2 + 1/R3 = 1/2 + 1/3 + 1/6 = 6/6 = 1/1

Rp = 1Ω

Q7. You must have come across the three R’s to save the environment :

Reduce, Recycle and Reuse. Explain Reduce in detail.

Ans. Reduce– This is all about reducing your use of harmful, wasteful and non-recyclable materials to save you money, help the environment and so on. By limiting your dependency on these types of products, this leads to less waste materials ending up in landfill and prevents you from creating negative impacts on the environment.

Q8.(a) An object is situated between the centre of curvature (C) and focus (F) of a concave mirror. Draw a ray diagram of the position, size and nature of image.

Ans.

Nature of image – A real, inverted image

Position of image – image is formed beyond the centre of curvature (C)

Size of image – It is larger than the object (enlarged image)

(b) Find the focal length of a lens of power -2.0 D. What type of lens is this ?

Ans. Power = 1/focal length (in meter)

F = 1/P = 1/(-2) = – 0.5 m = – 50 cm

The lens given is a Concave Lens as it has a negative value for power.

Q9. Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What are the advantages of ac over dc ?

Ans. Principle– In an electric generator, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity. It is working on the principle of electromagnetic induction.

Advantages of AC over DC : AC is less expensive and easy to generate than DC. The distance covered by AC is more than that of the DC. The power loss during transmission in AC is less when compared to DC.

(a) What do you mean by earthing ? Why should the electrical appliances be earthed ?

(b) What do you mean by a solenoid ? Draw the magnetic field lines around a current carrying solenoid. Write down the use of a solenoid.

Q10. Which reactant is reduced in the following chemical reaction ?

ZnO + C → Zn + CO

Ans. Zinc is reduced (due to gain in electron) and Carbon is oxidized (due to loss of electrons).

Q11. You have three solutions A, B and C, whose pH value is 3, 7 and 9 respectively. Out of above solutions, which solution is acidic ?

Ans. Solution A is Acidic (pH=3). We know that If pH<7 then Acidic, If pH=7 then Neutral, If pH>7 then Basic.

Q12. Element M forms a chloride with formula MCl3. Element M would be most likely in the same group of periodic table as :

(A) Si

(B) Al

(D) Mg

Ans. (B) Al

Q13. What do you mean by decomposition reactions ? Give one example (chemical equation).

Ans. If a single reactant breaks down to give two or more simpler products, it is called decomposition reaction.

CaCO3 + Heat → CaO + CO2

Q14. What is Chlor-alkali process ? Give chemical reaction for the process.

Ans. When electricity is passed through an aqueous solution of NaCl (brine) it decomposes to form sodium hydroxide. This is called chlor-alkali process because of the products formed − chlor for chlorine and alkali for sodium hydroxide.

2NaCl + 2H2O + Electricity → 2NaOH + Cl2 + H2

Q15. In modern periodic table, how does the atomic size vary in a period on moving from left to right ? Write its reason.

Ans. Atomic size decreases moving along a period. The nuclear charge increases on moving left to right in a period, which tends to pull the electrons nearer to nucleus and decreases the atomic size.

Q16. (i) What happens when water soluble metal oxides are dissolved in water ? Give one example.

Ans. Soluble metal oxides dissolve in water to form alkalis.

Na2O + H2O → 2NaOH

(ii) Why do ionic compounds have high melting point ?

Ans. ionic solids consists of aggregates of large number oppositely charged ions in a regular arrangement. These ions are held together by strong electrostatic forces of attraction. Hence considerable amount of energy is required to break the strong interionic attraction.

Q17. (i) Write the names of following compounds :

Ans.

(a) Propyne

(b) Methanol

(ii) Draw all the structural isomers of pentane (C5H12).

Ans.

Explain the following processes with help of chemical reactions :

(a) Esterification

(b) Saponification

Ans.

(a) Carboxylic acid react with alcohol in presence of acid to form esters (sweet smelling). This is called esterification.

(b) Ester on treatment with NaOH form alcohol and sodium salt of carboxylic acid. This reaction is called saponification, because it is used to prepare soap.

(c) Unsaturated hydrocarbons add hydrogen in presence of catalyst such as Pd or Ni to give saturated hydrocarbons. This is called hydrogenation.

Q18. The organisms which break down complex organic substances into simple inorganic substances and mix them in the soil :

(A) Producers

(B) Decomposers

(D) Carnivores

Ans. (B) Decomposers

Q19. Which part of neuron acquires information from sensory organs ?

(A) Cell body

(B) Dendrite

(D) Nerve ending

Ans. (B) Dendrite

Q20. In how many directions the energy flows in any ecosystem ?

Ans. Unidirectional (one direction)

Q21. Growth of facial hair and deepening of voice are symptoms of puberty in boys. Which hormone is responsible for it ?

Ans. Testoterone

Q22. In a flower, pollen tube enters through pistil into ovule. Name that part of pistil.

Ans. Stigma

Q23. What is difference between binary fission and multiple fission ? Explain with example.

Ans. Binary Fission– The parent cell divides itself into two equal and identical daughter cells. It is the most common form of reproduction in prokaryotes. It occurs during favorable conditions. It has a definite pattern of division. It divides only once. In this, both cytoplasm and nucleus divide together. Example- Bacteria, Amoeba, Euglena, etc.

Multiple Fission– The single parent cell is divided into many daughter cells. It is the most common type of reproduction in Protists and parasitic species. It occurs during unfavorable conditions. It does not have a definite pattern of division. It divides repeatedly. In this, the nucleus divides first and is surrounded by cytoplasm whose division occurs later. Example- Plasmodium, Algae, etc.

Q24. What are different contraceptive methods ? How are they important for reproductive health ?

Ans. Birth control, also known as contraception, is designed to prevent pregnancy. Preventing sperm from getting to the eggs. Types include condoms, diaphragms, cervical caps, and contraceptive sponges. Keeping the ovaries from releasing eggs that could be fertilized. Types include birth control pills, patches, shots, vaginal rings, and emergency contraceptive pills.

Q25. How are brain and spinal cord protected in human body ?

Ans. Brain is protected by a bony cavity called the skull or cranium in which brain is placed. The space between the brain and the skull is intervened by three meninges the duramater, pia mater and arachnoid membrane. The space between the meninges and the ventricles of the brain are filled with cerebrospinal fluid.

Spinal cord is protected with the help of the vertebral column, which is lined on the inner side by the meninges and cerebrospinal fluid.

Q26. A blue coloured flowering plant (BB) was crossed with white coloured flowering plant (bb). Explain with diagram.

(i) What will be the colour of flowers in F1 generation ?

Ans. In F1 generation, all plants will have a Blue flower.

(ii) What percentage of white flowered plants will be in F2 generation through self-pollination of F1 plants.

Ans. In the F2 generation, 25% of flowers are white in colour.

Q27. What is autotrophic nutrition ? Explain the process of photosynthesis in plants.

Ans. Autotrophic Nutrition– Autotrophic nutrition is a process where an organism prepares its own food from a simple inorganic material like water, mineral salts and carbon dioxide in the presence of sunlight.” The term “autotrophic” is formed by the combination of two terms, “auto” meaning self, and “trophic” meaning nutrition.

Process of Photosynthesis– Plants take up carbon dioxide from the atmosphere through the tiny pores known as stomata present on the surface of the leaves. Plants absorb the water and minerals from the soil with the help of roots and transport them to the leaves of the plant where the synthesis of food takes place. The green pigment, chlorophyll present in plant leaves, helps the leaves to capture sunlight. Sunlight is the source of energy to carry out photosynthesis. In the presence of sunlight, chlorophyll acts on carbon dioxide, minerals, and water to produce carbohydrates. These carbohydrates are stored in the plant leaves in the form of energy. The process of photosynthesis also releases oxygen into the atmosphere.

What is heterotrophic nutrition ? Explain the process of nutrition in Amoeba with diagram.

Ans. Heterotrophic Nutrition– Heterotrophic nutrition is the mode of nutrition where the organism is unable to prepare its food and hence, depends upon plants or other organisms for nutrition.

Process of nutrition in Amoeba :

ingestion– The process of ingestion is nothing but intake of food into the body. Amoeba is unicellular and hence it does not have mouth, Amoeba takes the food into the body by forming structures called pseudopodia around the food particle. This pseudopodia forms a vacuole around the food particle called food vacuole and the vacuole is taken inside the cell.

Digestion– The food particle inside the vacuole is broken down into soluble particles by digestive enzymes inside the vacuoles.

Absorption– The broken food particles is absorbed into the cytoplasm of amoeba by diffusion. The food particles which are unabsorbed are left inside the vacuole.

Assimilation– The absorbed food is converted into energy in this step.

Egestion– The undigested food in the food vacuole is thrown out from the cell.

It involves the ingestion, digestion and egestion of food material.

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