SCIENCE TECHNOLOGY PAPER THREE

Time : 3 hours        Max Marks: 80

SECTION 'A'

1. (A) Answer the following. (5)

(i) Fill in the blanks and rewrite the completed statements:. (2 Marks)

1. The Chemical formula of POP is _____________ (2CaSO₄H₂O)

2. Magnetic lines of force are __________ where the magnetic field is strong. (crowded)

(ii) Complete the analogy. (2 Marks)

1. CuCl₂ + 2KI → CuI₂ +2KCl : Double displacement ∷ Zn + 2HCl → ZnCl₂ + H₂ : _____________ (Displacement Reaction)

2. Tungsten : Conductor ∷ Ebonite : _____________ (Insulator)

(iii)Name the following : (1)

The quantity expressed in coulomb.

(Electric  charge)

 (B) Rewrite the following statements by selecting the correct  options: (5 Marks)

1. The second period contains ___________ elements.

a. 8

b. 2

c. 18

d. 32

2. Eucalyptus oil is known as __________

a. natural  indicator

b. olfactory indicator

c. synthetic indicator

d. universal indicator.

3. If a P.D.  of 12 V is applied across a 3 Ω resistor, then the current passing through it is _______

a. 36 A

b. 4A

c. 0.25A

d. 15A

4. When an object is placed between the focus and centre of curvature of a concave mirror, then image formed is __________

a. real and magnified

b. virtual and magnified

c. real and of the same size as that of the object

d. virtual and of the same size as that  of the object

5. In dispersion of sunlight by a glass prism, ____________ ray is deviated the least.

a. red

b. yellow

c. green

d. violet

2. Attempt the following. (10 Marks)

1. Elements in the same group show the same valency.

i.            Valency is the number of electrons given, taken or shared by an atom to complete its outermost shell.

ii.          All the elements in the same group have the same number of electrons in their outermost shells.

iii.        Thus, all these elements take, give or share the same number of electrons.

iv.         Hence, elements in the same group show the same valency.

2. What is corrosion? Do gold ornaments corrode? Justify.

Ans.

i.            The slow process of decay or destructions of a metal due to the effect of air, moisture, acids, alkalies, or other chemicals on it is called corrosion or rusting of iron. Its chemical formula is Fe₂O₃.H₂O.

ii.          Ordinarily, gold ornaments do not get corroded.

iii.        Gold is one of the least reactive metals. It does not react with air, moisture, sweat, or ordinary pollutants in air or water. Hence, it does not get corroded.

3. State application (uses) of baking soda.

Ans. The white amorphous powdered soda is termed as baking soda. Its chemical name is Sodium Hydrogen Carbonate or Sodium bicarbonate and its formula is NaHCO₃. When tested with litmus, NaHCO₃ turns red litmus blue, which indicates that it is alkaline in nature.

Sodium bicarbonate is extensively used in day – to – day life.

i.            It is used to prepare light spongy bread, cakes and dhokala.

ii.          It also helps to reduce acidity in stomach being alkaline.

iii.       It is very useful in preparing CO₂ gas and is one of the content of fire extinguishers. 

4. Distinguish between, Conductors and insulators.

Conductors	Insulators
1.  Those substances through which electricity can flow are called conductors. 2.  Electrical resistances of conductors are very low. 3.  They contain large number of free electrons. 4.  Generally metals are conductors. E.g. silver, copper, aluminium	1.  Those substances through which electricity cannot flow are called insulators. 2.  Electrical resistances of insulators are infinitely very high. 3.  They do not contain free electrons. 4.  Generally non – metals are insulators. E.g. wood, rubber, plastic

5.  P and Q are the two wires of same length and different cross sectional areas and made of same metal. Name the property which is same for both the wires and that which is different for both the wires.

Ans.

i.            The property which is same for both the wires is resistivity. 

ii.          The property which is different for both the wires is resistance.

6. Resistivity of some material is given below. State which one will be the best conductor.

Material	Copper	Aluminium	Silver	Nickel
Resistivity (Ωm)	1.62 x 10 – 8	2.63 x 10 – 8	1.60 x 10 – 8	6.48 x 10 – 8

 From the above table we find that of all the metals, silver has the lowest resistivity (1.60 x 10 ^{– 8} Ωm), which means that silver offers the least resistance to the flow of current through it. Thus, silver metal is the best conductor of electricity.

 3. Attempt the following (Any 5) . (15 Marks)

1. Fleming’s Left hand rule:

Ans. Stretch the forefinger, the central finger and the thumb of you left hand mutually perpendicular to each other. If the forefinger shows the direction of the field and the central finger shows the direction of the current, then the thumb will point towards the direction of the motion of the conductor.

2. Give scientific reasons: Alloys like alnico or nipermag are used in industry.

i.            Alloys like alnico or nipermag are very hard and are used in the production of permanent magnets.

ii.          Permanent magnets of these alloys are used in microphones, loudspeaker, ammeters, voltmeters, etc.

iii.        Alnico is an alloy of iron containing aluminium, nickel and cobalt. Nipermag is an alloy of iron containing nickel, aluminium and titanium.

iv.         Hence, permanent magnets prepared from these alloys are most suitable for use in industries.

3. Distinguish between: Convex mirror and concave mirror.

Convex mirror	Concave mirror
1.  It is called as diverging mirror. 2.  The light is reflected from outer surface. 3.  It can form only a virtual image.  4.  According to sign convention, focal length is positive.	1.  It is called as converging mirror. 2.  The light is reflected from inner surface. 3.  It can form a real image as well as virtual image.  4.  According to sign convention, focal length is negative.

4. Draw well labeled ray diagrams for image formation

A ray diagram for object at infinity for a concave mirror.

5. Explain how the formation of rainbow occurs.

Ans.

1.  The beautiful phenomenon of the rainbow is a combination of different phenomena – dispersion, refraction and reflection of light.

2.  The rainbow appears in the sky after a rain shower.

3.  The water droplets act as small prisms.

4.  When sunlight enters the water droplets present in the atmosphere, they refract and disperse the incident sunlight.

5.  Then they reflect it internally inside the droplet and finally again refract it.

6.  As a collective effect of all these phenomena, the seven coloured rainbow is observed.

6. Right hand thumb rule

Ans. Imagine that you are holding a current carrying straight conductor in your right hand such that the thumb points towards the direction current, then the curled fingers around the conductor will give the direction of the magnetic field. This is known as right hand thumb rule.

Q4. Attempt the following (any 1) ( 5 marks)

1.  Give Reason: Stars twinkle at night.

Ans.

i.            The stars emit their own light and they shine at night. The stars are point sources of light as they are very far away.

ii.          During refraction of starlight from the atmosphere, as starlight bends towards the normal, the apparent position of the star is slightly higher then its actual position.

iii.        Also this apparent position of the star is not stationary but changes slightly.

iv.         Because of mobility of air and changes in the temperature, the atmosphere is not steady. Hence refractive index of air in the given region goes on changing continuously and randomly.

v.           When the atmosphere refracts more light towards us, the star is seen bright. When the atmosphere refracts less light towards us, the star is seen dim. Thus due to change in the refractive index of atmosphere, stars appear twinkling at night. 

2. Find the expression for the resistors connected in series

. 

i.             Resistors connected in series: - If the number of resistance are connected one after another in such a way that the same current flows through each resistance, then the arrangement is called resistance in series.

1.  LetR_1, R₂ and R₃ are three resistances connected in a series combination and let R_s  be their effective resistance in the circuit. 

Let V_1, V₂ and V₃ be the P.D. across resistances R_1, R₂ and R₃ respectively. Let ‘V’ be the P.D. of the cell.   Let ‘I’ be the current flow through each resistance.

 According to Ohm’s Law,

                               

    

Conclusion:  If the resistors are connected in series then.

i.    In a circuit the current is the same in every part of the circuit.

ii.  The resistance of the combination of resistors is equal to the sum of the individual resistors.

iii.The total voltage across the combination is equal to the sum of the voltage drop across the separate resistors.

iv. The effective resistance in a series combination is greater than the individual resistances.

v.   This combination is used to increase resistance in a circuit.

Section B

5. (A) Say true or false with reason (5 Marks)

1. Organisms that depend on other organisms for their food are called autotrophic organisms.

Ans. False: Organisms that depend on other organisms for their food are heterotrophic organisms.

2. Proteins are the body building nutrients.

Ans. True.

3. The resemblances and the differences are due to heredity.

Ans. True.

4. Multiple fission is carried out only during favourable period.

Ans. False: Multiple fission is carried out only during unfavourable period.

5. Covalent compounds are soluble in organic solvents.

Ans. True.

(B) Rewrite the following statements by selecting the correct  options: (5 Marks)

1. The division of cytoplasm through ________ plane is called simple binary fission.

a. transverse

b. longitudinal

c. any

d. diagonal

2. __________ is a metalloid.

a. Aluminium

b. Antimony

c. Zinc

d, Mercury

3. Organs which are fundamentally the same in structure, but modified for widely different functions are called known as _______ organs.

a. analogous

b. homologous

c. vestigial

d. functionless

4. __________ is the stalk of anther.

a. Stamen

b. Ovule

c. Filament

d. Style

5. Muscle cells contain special type of ______ which are capable of bringing about change in their shape.

a. starch

b. protein

c. fat

d. salt

6. Attempt the following. (10 Marks)

1. How can we save energy in day to day life?

In day to day life we can save energy by reducing the consumption of fuels. Reduction is possible by efficient usage of energy, wastage elimination and awareness.

This can be achieved by measures like:

i.            Controlling usage of electricity by using power saver lamps and appliances.

ii.          Switching off the appliances when not in use.

iii.        Using public transport instead of private motorized vehicles etc.

2. write a short notes on Chipko movement:

i.            Chipko is a pioneering movement in environment conservation in India.

ii.          It was first initiated in the Marwad region of Rajasthan by the Bishnoi community.

iii.        The principle behind 'Chipko' is 'hug the tree' to prevent it from being felled.

iv.         This simple principle was used in the Himalayas in the 1970s to protect the forest from contractors.

v.           When the forest was to be auctioned for timber extraction, the local community started a 'Chipko movement' in that area and protected the forest.

3. The use of fossil fuels in villages.

The following measures helps to reduce the use of fossil fuels:

i.            Rather than depend on fossil fuels, use energy from renewable (non conventional) sources like solar energy, biogasplant, windmill etc.

ii.          Different types of engines are being used for various purposes. These engines are constantly consuming the sources of energy such as coal, petroleum etc. To reduce the use of fossil fuels, engines that reduce emissions to a large extent can be built and Compressed Natural Gas (CNG) can be used.

4. In human beings the gametes from the male parent decides the sex of the baby.

i.            In human beings there are 22 pairs of autosomes and 1 pair of sex chromosome.

ii.          In human male gametes, two dissimilar sex chromosomes XY are present whereas in females two similar sex chromosomes XX are present.

iii.        All children inherit 'X' chromosomes from their mother and 'X' or 'Y' from their father.

iv.         If it is X chromosome from father, then the offspring will be a daughter and if 'Y' chromosomes, then it will be son.

v.           Hence, the gametes from the male parent decides the sex of the baby.  

5. Short notes on Multiple fission

i.            During unfavourable condition, the amoeba withdraws its pseudopodia, becomes almost round and secretes a hard covering called cyst.

ii.          Inside the cyst nucleus divides into many nuclei by repeated division, follow by division of cytoplasm.

iii.        As a result many daughter cells are formed.

iv.         The cyst bursts to release the daughter cells during favourable condition.

6. What does this log indicate? Write some names of products on which you find this logo.

This logo indicates Recycle.

This logo is found on plastic articles such as bottles, toys, furnitures, paper bags and electronic equipments etc.

7. Attempt the following. (10 Marks)

1. Draw a well labelled diagram of: Longitudinal section of flower.

2. Write the functions of the following organs in reproduction.

1.  Vagina

i.            It provides the route for the menstrual blood to leave the body during menstruation.

ii.          It is a pathway through which sperms enters into woman’s body.

iii.        It is a pathway through which a baby comes out of the woman’s body during child birth.

2.  Stigma

i.            It receives pollen grains and on which pollen germinates.

3.  Ovaries

i.            Ovaries develop and release eggs into the oviduct.

ii.          It secretes hormone estrogen.

4.  Seminal vesicle and Prostate glands

i.            Produce ejaculatory fluid which helps the sperm in transport and provides nutrition.

5.  Uterus

i.            It accommodates a growing foetus.

ii.          It push the baby during labour.

3. Give scientific reason: Hormones secreted by the endocrine glands are present everywhere in the body.

i.            Endocrine glands do not have ducts to store or transport their secretions called hormones.

ii.          The hormones are directly released into the blood stream and reach concerned body parts through blood.

iii.        Hence, hormones secreted by the endocrine glands are present everywhere in the body.

4 . Explain the process of translocation in plants.

Ans.

i.            Transport of nutrients from leaves to other parts of the plant is called translocation.

ii.          It takes place through phloem in upward as well as downward direction.

iii.        This process needs energy which is obtained from ATP.

iv.         When food materials like sucrose are transferred to phloem tissue, using ATP, the concentration of water molecules decreases in that area.

v.           This results in the movement of water into the cells due to osmosis.

vi.         The increased contents within the cells exert a high amount of pressure on their wall.

vii.       This pressure moves the food materials to the adjacent cells with low pressure.

viii.     This allows the phloem to move material according to the plant’s needs.

5. How are fats digested in the human body?

i.            Liver, the largest gland in the body secretes bile juice which is stored in the gall bladder.

ii.          Whenever food enters the small intestine, the gall bladder releases bile into it through a duct.

iii.        Bile makes the food alkaline and breaks the large fat globules into smaller ones, this increases the enzyme action.

iv.         Pancreas secretes digestive juice. It has digestive enzymes like lipase which help to break down fats.

v.           Various intestinal juices are also secreted by the walls of the small intestine to complete the digestion process of converting fats into fatty acids.  

6. Write short notes on Eutrophication

i.            The enrichment of water bodies by inorganic plant nutrients like nitrate, phosphate occurring either naturally or due to human activity is Eutrophication.

ii.          The process of eutrophication takes place due to introduction of nutrients and chemicals through discharge of domestic sewage, industrial effluents and fertilizers from agricultural fields.

iii.        These promote excessive growth of phytoplankton and algae. When algae die, decomposition of organic substance use oxygen.

iv.         This results in depletion of oxygen in water. The bloom of algae blocks penetration of oxygen, light and heat into the water body. As a result most of the organisms die below the surface of the water.

 8. Attempt the following (any 1) (5 marks.)

1. Explain the structure and function of a nephron.

Ans.

i.            The basic filtration unit in the kidney is a cluster of thin walled blood capillaries called as nephron.

ii.          Each nephron has a cup shaped thin walled upper end called Bowman’s capsule which contains a bundle of blood capillaries called glomerulus.

iii.       When blood containing urea enters the glomerulus it gets filtered through glomerular capillaries.

iv.        The selectively permeable wall of the Bowman’s capsule allows the water molecules and small molecules of the other substances to pass through them and forms glomerular filtrate.

v.           The blood, free from these materials is taken to the heart through the renal vein.

vi.        The glomerular filtrate collected in the Bowman’s capsule further passes through the nephron tubule where reabsorption of water and useful molecules take place.

vii.      The remaining fluid containing the waste forms the urine which eventually enters a long tube called the ureter.

viii.    It is further stored in the urinary bladder and from there it is thrown out through the urethra.

2 The plants are kept in dark before determining the factors essential for photosynthesis.

              i.        When plants perform photosynthesis, they produce carbohydrates. These carbohydrates are used for their growth and energy.

            ii.        The unutilized carbohydrates are stored in the form of starch.

          iii.        While performing experiments on photosynthesis, it is necessary that this stored starch is completely used up.

           iv.        When the plant is kept in dark, it utilizes this stored starch and becomes destarched.

             v.        The factors essential for photosynthesis such as carbon dioxide, sunlight and chlorophyll can be studied with such destarched plant. Thus, the plants are kept in dark before determining the factors essential for photosynthesis.