Science Question Paper with Solution.

SCIENCE QUESTION PAPER WITH SOLUTION

Section A


1. (A) Answer the following sub - questions.  (5 Marks)

*1. The device used for producing current is called a ..................... .
(a) voltmeter (b) ammeter (c) galvanometer (d) generator

*2. At the time of short circuit, the current in the circuit ..................... .
(a) increases (b) decreases (c) remains (d) increases in steps

*3. The direction of the magnetic field around a straight conductor carrying  current is given by .....................
(a) right hand rule (b) Fleming’s left hand rule (c) Fleming’s right hand rule (d) none of these

4. The relation between electricity and magnetism was first established by  ..................... .
(a) Ohm (b) Ampere (c) Oersted (d) Moseley

5. The region around magnet is called as .............. .
(a) magnetic Area (b) magnetic field (c) magnetic loop (d) magnetism

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

1. The image formed by a concave mirror is ..................... .

(a) always virtual and erect       (b) always virtual and inverted
(c) virtual if the object is placed between pole and focus (d) virtual if the object is beyond focus

2. A concave mirror forms a virtual image of an object placed ..................... .

(a) at infinity         (b) at the centre of curvature of the mirror
(c) at the focus of the mirror      (d) between the focus and the mirror

3. A convex mirror always forms an image which is ..................... than the object size.

(a) larger (b) smaller  (c) double (d) three times

4. No matter how far you stand from a spherical mirror, your image appears erect. The mirror may be ...........   

 (a) Plane (b) concave  (c) convex (d) either plane or convex

5. In case of a concave mirror, an erect image is ..................... .

(a) real and enlarged (b) real and diminished (c) virtual and diminished (d) virtual and enlarged


2. Attempt the following. (10 Marks)

1.   Atomic size increases down the group.

i.             The atomic numbers of the elements increase as we go down the group. Thus, the elements placed lower have more electrons.
ii.           To accommodate these electrons new shells are added to the atom.
iii.          These new shells take the outermost electrons farther from the nucleus causing atomic size (radius) to increase as we go down the group.

2.   What is the importance of a chemical equation?

Ans.  A chemical equation can convey the following information.
i.             Reactants and products involved in the reaction.
ii.           Symbols and formulae of all substances involved in the reaction.
iii.          Relative number of reactants and product participating in the reaction.
iv.          Relative masses of reactants and products.
v.            Physical states of reactants and products.  

3.   Write short notes on Indicators (with proper example).

Ans. The acidic and basic nature of the compounds can also be indicated by some natural as well as chemical substances. They are known as indicators.
i.             There are many natural substances such as rose petals, turmeric, beet root, etc that can be used as indicators. They are called natural indicators.
ii.           Some chemical substances such as phenolphthalein, methyl orange, eosin are synthetic indicators.
iii.          Olfactory indicators: Substances whose odour changes in acidic or basic solution are called olfactory indicator. An olfactory indicator works on the principle that when an acid or base is added to it, then its odour cannot be detected. Examples: onion and clove extract.
iv.          Universal indicators: Universal indicator is a mixture of several indicators which gives different colours at different pH values of the pH scale.
v.            Uses of indicators: The acidic or basic nature of a compound can be judged. It is used in agriculture to determine the pH of the soil.

4.   Give Scientific Reason : The material used for fuse has low melting point.

i.             A fuse is used to protect a circuit and the appliances connected in the circuit by stopping the flow of an excess electric current. For this, a fuse is connected in series in the circuit.
ii.           When the current in the circuit passes through the fuse, its temperature increases. When the current exceeds the specified value, the fuse must melt to break the circuit. For this, the material used for a fuse has low melting point.

5.    Define

1.   Magnetic field: -The region around magnet, in which the force of attraction and repulsion exists, is called as ‘magnetic field’.

2.   Solenoid: -A coil of many turns of insulated copper wire wrapped in the shape of cylinder is called a solenoid.


3. Attempt the following. (10 Marks)

1.   Refraction observed in the atmosphere.

i.             In the atmosphere, there are different layers of air with different refractive indices which keep on changing as the physical conditions of air are not stationary (still).
ii.           When we observe any object through this air, the light coming from them refract randomly due to which the apparent position of the object fluctuates.
iii.          The large scale effect of this phenomenon is the twinkling of stars, advanced sunrise and delayed sunset.
iv.          Due to change in the refractive index of atmosphere, the intensity of light that reaches our eyes from the stars varies and hence the stars appear twinkling at night.
v.            Advanced sunrise occurs as a ray of light from the sun enters the earth’s atmosphere; it follows a curved path due to refraction before reaching to the observer.
vi.          It appears to the observer as if the rays are coming from the position where the sun is seen by the observer, hence, the sun is seen earlier before it reaches the horizon.




2.   Explain Hypermetropia with its correction.

·         It is the defect in which human eye can see distant objects clearly but is unable to see nearby objects clearly.
·         The image of near object falls behind retina. Two possible reasons of Hypermetropia are :
·        Weak action of Ciliary muscles causes low converging power of eye lens.
·        The distance between eye lens and retina decreases on account of either shortening of eyeball or flattening of lens. In this case focal length of the eye lens is too long.
·        A convex lens of suitable focal length can correct this defect.
·        The rays coming from nearby object are first converged by convex lens and then converged by eye lens to retina.

3.   State any 5 Application of Convex lens:

·        Simple microscope: A single convex lens of small focal length can be used as a simple microscope. A magnification of about 20 times is obtained by simple microscope. Watch repairers, jewelers, etc use it.
·        Compound microscope: A combinations of two convex lenses having short focal lengths are used in compound microscope. It is used to observe bacteria, viruses, cells, micro – organisms, etc.
·        Telescopes: A combination of two convex lenses is used in telescopes. An astronomical telescope is used to get detailed view of astronomical bodies like planets, stars, etc. Terrestrial telescope is used to study terrestrial objects.
·        Optical instruments: Convex lenses are used in different optical instruments like camera, projector, spectrometer, etc.
·        Spectacles: Convex lens is used in spectacles to correct defect like Hypermetropia

4.   Explain the sign conventions for reflection by spherical mirrors.

According to the new Cartesian sign convention, the pole (P) of the mirror is taken as origin. The principal axis is taken as X-axis of the co-ordinate system. The sign conventions are as follows:

·        The object is always placed on the left of the mirror.
·        All distances parallel to principal axis are measured from the pole of the mirror.
·        All the distances measured to the right of the origin are taken as positive, while distances measured to the left of the origin are taken as negative.
·        Distances measured perpendicular to and above the principal axis are taken as positive.
·        Distances measured perpendicular to and below the principal axis are taken as negative.
·        Focal length of convex mirror is positive while that of concave mirror is negative.

     



  5.   Distinguish between Myopia and Hypermetropia

Myopia
Hypermetropia
1.   In this defect human eye can see nearby objects distinctly but is unable to see distant objects clearly.
2.   Image of distant object is formed in front of retina. 
3.   Eye ball is lengthened or lens is curved.
4.   This defect is corrected using concave lens.
1.   In this defect human eye can see distant objects distinctly but is unable to see nearby objects clearly.
2.   Image of nearby objects falls behind retina.
3.   Eye ball is shortened or lens is flattened.
4.   This defect is corrected using convex lens.


Q4. Attempt the following ( 5 marks)

1.  How could the modern periodic table remove various anomalies of Mendeleev’s periodic table?

i.        Hydrogen was placed in group 1 and in group 17 as it resembles alkali metals as well as halogens. Therefore, no fixed position could be given to hydrogen in Mendeleev’s periodic table.  But in Modern periodic table it is placed in group 1.
ii.      Mendeleev arranged the elements in their increasing order of atomic masses. But some elements with higher atomic masses are placed before those having lower atomic masses. E.g. Cobalt (Co) with atomic mass 58.93 is placed before Nickel (Ni) having atomic mass 58.71. But in Modern periodic table the elements were arranged on the basis of the atomic number of elements. Thus atomic number of Co is 27 and that of Ni is 28. So Nickel is placed after Cobalt.
iii.    Though isotopes of the same elements have different atomic masses, they cannot be placed separately in the periodic tale. Since isotopes are chemically similar, they had to be given the same position in the periodic table. Isotopes occupy the same position in the Modern periodic table.
iv.   In Modern periodic table elements are classified according to their electronic configuration into different blocks. Thus, various anomalies (irregularity) which were seen in Mendeleev’s table due to the arrangement according to atomic masses were overcome by the Modern Periodic table.  





Section B

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

*1. In ..................... mode of reproduction, the offsprings are with minor differences.

*2. Both the parents contribute equal amount of ..................... material to the offspring.

*3. Dominant character masks the ..................... character.

*4. Selection by nature is not ..................... but ..................... .

5. Mendel’s experiments were based on a number of visible contrasting characters of garden peas ..................... .

Answers....

·        Asexual
·        Genetic
·        Recessive
·        Deliberate, natural
·        Pisum sativum

(B) Say true or false with reason  (5 Marks)

1. A fragment of DNA that provides complete information about one protein is known as the ..................... for that protein.

2. All children inherit ..................... chromosome from their mother.

3. 3. Sex determination in human beings is ..................... .

4. ..................... are collected from different levels of depths.

5. Minor differences occur in asexual reproduction due to inaccuracies occuring in ..................... .

Answers: -

·        Gene
·        X
·        Genetical
·        Fossils
·        DNA copying

2. Attempt the following. (10 Marks)

1.  State two functions of MPCB for prevention of water pollution.

MPCB is the Maharashtra Pollution Control Board. Their functions are:
i.            To plan comprehensive programmes for the prevention, control or abatement of pollution.
ii.          To inspect sewage or trade effluent treatment and disposal facilities.
iii.        To support and encourage the developments in the fields of pollution control, waste recycle, reuses, eco – friendly practices, etc.
iv.         To educate and guide the entrepreneurs in improving environment by suggesting appropriate pollution control technologies and techniques.
v.           To create public awareness about the clean and healthy environment and consider the public complaints regarding pollution.

2.  Define eco – efficiency. What are the ways to achieve eco – efficiency?

Eco – efficiency mean the creation of goods and services using fewer resources and creating less waste. Eco – efficiency can be achieved by:
i.            Use of alternative raw materials: e.g. Agricultural  residues like rice straw and wheat straw are good substitutes for wood.
ii.          Shifting to renewable sources of energy: e.g. renewable sources of energy such as biofuels, solar power, wind power, tidal power, hydropower, geo – thermal power etc. do not create pollution and are inexhaustible.
iii.        Technology that reduces pollution: e.g. solar water heater, solar cooker, wind mills etc. Are examples of pollution free technologies. Use of CNG and unleaded petrol in vehicles also reduces pollution.
iv.         Reusing and recycling waste: e.g. waste products like paper, glass, plastics and metals can be recycled to make new products.
v.           Durable goods: e.g. use of fibre optic cables in place of copper telephone wire not only reduces the use of mineral sources but also provides better communication.

3. Give the impacts of Noise pollution on the human body.

Effects of noise pollution on human beings depend on noise intensity, frequency and exposure duration.
There are three types of effects on man:
i.            Auditory effects: Auditory fatigue, deafness.
ii.          Non – auditory effects: Communication interference, sleep interference, concentration interference, ill temper, annoyance, violent behaviour, mental disorientation, bickering and lose of working efficiency.
iii.        Physiological effects: Nausea, fatigue, anxiety, visual disturbances, insomnia, hypertension, cardio vascular disease.

4.  Distinguish between Degradable and Non degradable pollutants.

Degradable pollutants
Non degradable pollutants
1.  Degradable pollutants can be decomposed or degraded easily.
2.  Decomposition takes place by microorganisms and it requires less time.
3.  These pollutants again enter the biogeochemical cycles and become part of the natural nutrient cycle.
1.  Non – degradable pollutants cannot be easily decomposed.
2.  It requires more time and different techniques for decomposition.
3.  These pollutants will remain on the earth for years and create environmental pollution.

5. What are the advantages of sexual reproduction over asexual reproduction?

i.            The offsprings produced by sexual reproduction are different from parents.
ii.          Variations give rise to variety and diversity.
iii.        Variation enables organisms to adapt and survive in the changing environment.
iv.         It helps to prevent the complete extinction of animal and plant species.


3. Attempt the following. (10 Marks)

1. Write the functions of

a.  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.
b.   Stigma
i.            It receives pollen grains and on which pollen germinates.
c.   Ovaries
i.            Ovaries develop and release eggs into the oviduct.
ii.          It secretes hormone estrogen.




2. Write short notes on Reflex action

·        The sudden action in response to some happenings in the environment is called as reflex action.
·        It is an involuntary action which we perform automatically.
·        The path way taken by nerve impulses in a reflex action is called reflex arcs. Reflex arcs allow rapid response.
·        A nerve from all over the body meet in a bundle in such a connection is commonly called as the spinal cord, before impulses are sent to the brain.
·        Hence, reflex arcs are formed in the spinal cord, although the messages reach the brain.
·        Pulling away our hand on touching a hot object, narrowing of the eyes in sunlight, watering of the mouth on smelling something delicious etc. are examples of reflex action.

3. Explain the structure and function of a nephron.

·        The basic filtration unit in the kidney is a cluster of thin walled blood capillaries called as nephron.
·        Each nephron has a cup shaped thin walled upper end called Bowman’s capsule which contains a bundle of blood capillaries called glomerulus.
·        When blood containing urea enters the glomerulus it gets filtered through glomerular capillaries.
·        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.
·        The blood, free from these materials is taken to the heart through the renal vein.
·        The glomerular filtrate collected in the Bowman’s capsule further passes through the nephron tubule where reabsorption of water and useful molecules take place.
·        The remaining fluid containing the waste forms the urine which eventually enters a long tube called the ureter.
·        It is further stored in the urinary bladder and from there it is thrown out through the urethra.

4 . Differentiate between: Detergents and soaps

Detergents
Soaps
i.            Detergents are generally ammonium or sulphonate salts of long chain carboxylic acids.
ii.          Detergents have a strong cleansing action.
iii.        Oils or fats are not used in their manufacture; usually petrochemicals are used to produce detergents.
iv.         They function well in hard or soft water.
i.            Soaps are sodium or potassium salts of long chain carboxylic acids.
ii.          Soaps have relatively weak cleansing action.
iii.        Vegetable oils or animal fats are used along with hydroxide of sodium or potassium to manufacture soaps.
iv.         They do not work well in had water but work well in soft water.

5. Give scientific reasons : Calcium floats over water during the reaction with water.

Ans.
i.            Calcium reacts with water less vigorously so that the heat evolved is not sufficient for the hydrogen formed, to catch fire.
ii.          Instead, calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of the water calcium.


4. Attempt the following (5 marks.)

Darwin’s theory of evolution. Or Darwin's theory of Natural Selection.
·        Darwin's theory of evolution is better known as theory of Natural selection.
·        Darwin opined that only the fittest can survive. Those plant and animals which are not fit for survival, die.
·        The fitter species reproduce in greater numbers and pass on their genes to the next generations. This process of selection of characteristics which contribute to the fitness for survival was termed as natural selection.
·        Darwin's theory of Natural selection emphasises on the fact that there is always overproduction of individuals in nature. This causes struggle for existence. Only those organisms that have characters useful for survival are selected and hence they survive.
While some organisms that do not have favourable characters, perish. This process takes place for many generations.   
·        As a result the species which are better adapted for survival are selected. The individuals belonging to this species may be different from the original ones. But if this changed species shows successful adaption and growth in the given environment then it gets evolved.
·        The process of natural selection is not deliberate but is gradual and natural. This process further leads to the development of species.
·        Darwin's theory is widely accepted but it has one drawback. It did not explain how the favourable characters were developed in the fit individuals.
·        Darwin's theory is now universally accepted.