Section A
Q.1. Choose the correct answer : 

1. The pH value of pure water is :

(a) 7 ✅

2. The pH value a solution is 4 then the solution is :

(c) Acidic ✅

3. Which of the following is most reactive metal :

(c) Sodium ✅

4. Law of octaves was given by :

(a) Newland ✅

5. example of symbiosis is :

(d) Lichens ✅

Q.2. Fill in the blanks :

1. Amoeba is a Unicellular  organism. 

2. The Mid brain is responsible to receive auditory and visual impulses.

3. The ear muscles and wisdom teeth are Vestigial organs of human.

4. The focal; length of a spherical mirror is Half of its radius of curvature.

5.The least distance of distinct vision of healthy human eye is 25cm.

Q.3. Match the columns :

Q.4. Answer the following in one word/sentence :

1. State name of perfect parasitic plant.
Ans. Rafflesia.

2. What is function of pheromone ?
Ans. To attract the insects.

3. Name the scientist who first propounded the structure of gene.
Ans. Sutton.

4. Which lens is use for connection of hypermetropia ?
Ans. Convex lens.

5. The collection and use of rainwater is called ?
Ans. Rainwater harvesting.

Section B

Q.5. Why do we apply paint on iron articles ?
Ans. We apply paint on iron articles because paint acts as antioxidant and saves iron from corrosion. 
  oil and fat containing food items are flushed with nitrogen. why ?
Ans.When the oil and fat containing food items comes into contact with air they get oxidized. To keep these items save from oxidising effect, they are flushed with nitrogen.   

Q.6. Why do you think the noble gases are placed in a separate group ?
Ans. according to our opinion, noble gases are chemically inert because their outer most orbit are completely filled. Hence their the properties of inert ( Noble ) gases are similar bu are different from other elements. so, they are justified to be placed in a separate group.
     In first period of periodic table only two elements are there. Why ?
Ans. Since the elements of first period has only one shell in which maximum two electrons can remain.So in first period of periodic table only two elements are there.
Q.7. Differentiate between self and cross pollination. ( Any four ) 
    Compare the growth in animals and plants.

Q.8. write the silent features of gene concept.
Ans. (i) Gene show reoccurrence.
(ii) Gene are located on chromosomes.
(iii) Any gene can found in more than one position.
(iv) Genes are arranged as a garland  of beads on chromosomes.
(v) Each gene is located at a specific place on a specific chromosomes.
(vi) Gene is a physical unit which is transmitted to generation to generation from parent's generation.
    What is chromosome ?
Ans. Chromosome ; A thread like structure of  nucleic acid and protein found in nucleus of most living cell, carrying genetic information in the form of genes.

Q.9. What is power of lens ? 
Ans. The reciprocal of focal length ( metre ) is called power of lens, its unit is dioptre.
    What is meant by rarer and denser medium ?
Ans. The medium whose optical density is is called denser medium which the medium whose optical density is less, are called rarer medium.
Q.10. A solution of X substance X is used for white washing :
              (i) Name the substance X and write its formula.
              (ii) Write the reaction of the substance x named in (i) above with water.
Ans. (i) The name of substance X is quick lime. Its chemical formula is CaO.
         (ii) Cao(s)+H2O⟶Ca(OH)2(aq) 
                                                  ( slacked lime)
 in the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. write the reaction involved.
Ans. In the refining of silver, when the copper is added to the silver nitrate solution, it displace the silver because copper is more reactive than silver.

Q.11. Write down uses of lenses.
Ans. (A) Uses of convex lens :  (i) These lens are used in microscope, telescopes and camera etc.
(ii) these lens are used to correct the long sightedness and presbyopia.
(iii) They are used as magnifying glass by watch maker.
(iv) They are used as reading lenses.
(v) They are used by palmist and fingerprint experts.
(B) Uses of concave lenses : (i) In Galilean telescope. 
(ii) These lens are used to correct the short sightedness.
(C) Uses of cylindrical lenses : (i) To correct the astigmatism.
       What is long sightedness ? Explain by diagram that how it can be removed.
Ans. Long sightedness : Person cannot see the nearby objects clearly. It can be removed by using convex lens.

Q.12. Write faraday's law of elecromagnetic induction.
Ans. There are two laws given by faraday which are :
(i) Whenever there is some changes in magnetic flux linked with a coil then an induced electromotive force is developed across the ends of coil and hence current flows through the coil.
(ii) The induced electromotive forced is directly proportional to the rate of change of magnetic flux.
       Define induced current. Why they are produced ?
Ans. The produced in a coil due to relative motion between the coil and the magnet is called induced current.
            due to relative between the coil and magnet the flux linked with the coil changes. Hence the induced current is developed .

Q.13. When current is allow to flow through coil of an electric motor, it rotates why ?
Ans. When current is allow to flow through coil of an electric motor, a torque acts on it, which rotates the coil about, its axis.

Q.14. What precautions should take while using L.P.G. in houses ?
Ans.  The following precautions should take while using L.P.G. in houses :
(i) The rubber tube should be tested time to time periodically.
(ii) Gas regulator should not be left open while the gas is not being used.
(iii) The windows and doors should be opened immediately when smell of gas is obtained.
(iv) Burning substance should not be brought near the gas.
        Due to combustion of petroleum, pollution is produced. why ?
Ans. during combustion of petroleum, pollution is produced because :
(i) petroleum products are mixture of several hydrocarbons, which on burning give CO2 on complete oxidation and carbon monoxide (CO) and partial oxidation.
(ii) In petroleum, nitro, compounds are present, which on burning give oxides of nitrogen.
(iii) In petroleum sulphur compounds are presen, whioch on burning give sulphur-dioxide and sulphur tri-oxide.
(iv) Oxides of lead are produced by combustion of petroleum because lead is present in it.

Section D

Q.15. While diluting an acid, why is it recommended that the acid should be added to water and not water to acid ?
Ans. Curd and sour substances are acidic in nature and they react with brass and copper so they should not be kept in these vessels.
Why should curd and sour substances not be kept in brass and copper vessels ?
Ans. The dilution process of acids in water is highly exothermic. A large amount of heat is involved in this process. So in the dilution process precautions should be taken. The acid should be added to water very slowly and continuous shaking. On the other hand if water is added to acid due to sudden release of heat it might spill on your body and clothes.

Q.16. Explain the formation of scum when hard water is treated with soap ?
Ans. the addition of hydrogen to unsaturated hydrocarbon in the presence of catalyst is known as hydrogenation.
    What is hydrogenation / what is its industrial application ?
Ans. In hard water, the carbonate, and bicarbonate of calcium and magnesium are present. They react with soap and from non-dissolving substances. These are called 'scum' so the soap cannot give from in hard water and more soap is used.

Q.17. Draw a labelled diagram of structure of Nephron.
How are the fat digested in our bodies ? Where does this process take place ?
ans.  Digestion of fat of take place in small intestine. It takes secretion from the pancreas and liver of the digestion of fat with the help of enzymes obtained from pancreas. The food is made basic (Alkali).It is done by bile juice. In small intestine, the fat is in the from of large globules. The bile salt break these globules into small globules. Now an enzyme named as lypase converts the fat into fatty acid and glycerol.

Q.18. Write names and functions of two hormones secreted by the thyroid gland.
Ans.  (1) Thyroxin : It effect the metamorphosis in the larva of frog.
(2) It controls and regulates the heat production.
(2) Thyrocalcitonin :  It regulates the quality of calcium in blood.
How does our body respond when adrenaline is secreted into the blood ?
Ans.  Adrenaline is secreted into the blood and is sent to various past of the body target organs or the specific tissues on which it acts include the heart. As a results the heartbeats faster, resulting in supply of more oxygen to our muscles. The blood to the digestive system and skin is reduced due to contraction of muscles around small arteries in these organs. this diverts the blood to our skeletal muscles. The breathing rate also increases because of the contractions of the diagram and rib muscles. All these responses together enable the animal body to be ready to deal with the situation.

Q.19 Will current flow more easily through thick wire or a thin wire of the same material, when connected to the same source. Why ?
Ans. The current will flow easily through thick wire, because the resistance of conductor is inversely proportional to its area of cross section.  Due to this reason the resistance of thick wire will be less than that of thin wire so the current flow more easily through it.
Section E
Q.20. Define the following terms : (i) minerals, (ii) Ores, (iii) Gangue.
Ans. (i) Minerals : the elements or compounds which occur naturally in the earth's crust are known as minerals.
(ii) Ores : At some place minerals contain a very high percentage of a particular metal and the metal can be profitable extracted from it. These minerals are  called ores.
(iii) Gangue : Ores mined from the earth are usually contaminated with large amount of impurities such as soil, sand etc. called  gangue.
carbonate and Sulphide ores are usually converted into oxides during the process of extraction. why ?
Ans. It is easier to reduce oxide into metal. So carbonate and sulphide ores are usually converted into oxides during the process of extraction.

Q.21. define fission and explain it with example of  unicellular organism.
Ans.  Fission is a method of asexual reproduction. In several unicellular organisms when the individual cell is fully mature, it divides into two. In this division first the nucleus of the cell divides and then the cytoplasm to from two daughter cells which grow and take the from of mother cell. sometimes a cell divides to from more than once cell and then it is known as multiple fission, whereas  first method is called binary fission. e.g., Amoeba.
     Describe with diagram the reproduction in hydra by budding process.
Ans. In the beginning small swellings appear on the surface of hydra these outgrowth develop into buds. the buds become matured and grow into daughter hydra. these daughter hydras separate from mother hydra and grow independently.

Q.22. Why are prefer the convex mirror to use as rarer view mirror ? 
Ans. The convex mirror are used as rear view mirror in vehicles because they form the erect, virtual and diminished image of the object. Due to this the driver is able to see the back view.