SCIENCE TECHNOLOGY PAPER TWO SSC MAHARASHTRA STATE BOARD

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. Elements showing properties of both metals and non – metals are known as ________ (metalloids)

2. The chemical reactions in which heat is liberated are called ________ reactions.

(exothermic)

(ii) Complete the analogy. (2 Marks)

1. Glass : Insulator ∷ Copper : __________ (Conductor)

2. CuI₂ : Brown ∷ AgCl : ________ (White)

(iii) Find the odd one out:

Loudspeaker, Microphone, Electric motor, Bar Magnet.

Ans. Bar magnet.

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

1. The modern periodic table is based on ________

a. the principle of octaves

b. the atomic number of elements

c. the atomic mass of elements

d. the presence of traids of elements

2. The colour of phenolphthalein indicator in  a basic solution is _______

a. yellow

b. green

c. orange

d. pink

3. 1 kilowatt hour = _______

a. 4.6 × 10⁶ joules

b. 3.5 × 10⁶ joules

c. 30.6 × 10⁶ joules

d. 3.6 × 10⁶ joules

4. The apparent depth of swimming pool is ________ the real depth.

a. less than

b. greater than

c. equal to

d. half

5. When an object is placed at the centre of curvature of a concave mirror, the 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.

2. Attempt the following. (10 Marks)

1. Metallic character decreases from left to right in a period.

i.             Atoms of metals tend to lose electrons, whereas those of non – metals tend to gain them.

ii.           In a period, as we go from left to right, atomic number increases, increasing the number of electrons and protons.

iii.          These additional electrons are placed in the same outer shell and are strongly attracted towards the positively – charged nucleus.

iv.          This strong attraction does not allow loss of electrons, causing metallic character to decrease from left to right in a period.

2. What do you understand by the term “Redox Reactions”? Explain with one example.

Ans.

i.             When oxidation and reduction take place simultaneously in a given chemical reaction, it is called redox reaction or oxidation-reduction.

ii.           No oxidation can take place without reduction and there is no reduction without oxidation at the same time.

iii.          When carbon monoxide is passed over heated ferric oxide, carbon monoxide gains oxygen (i.e. gets oxidized) to form carbon dioxide. At the same time, iron oxide gets reduced to metallic iron by the loss of oxygen.

iv.          Fe₂O₃ + CO → 2Fe +2CO₂ ↑

3. Write short notes on Water of crystallization (with proper example

Ans.

i.             Water of crystallization is the fixed number of water molecules present in the crystal structure.

ii.           For example, chemical formula of hydrated copper sulphate is CuSO₄.5H₂O. Copper sulphate has 5 molecules of water of crystallization.

iii.          Sodium carbonate is Na₂CO₃.10H₂O. Sodium carbonate has 10 molecules of water of crystallization.

iv.          On heating or on exposure to air, the above salts lose water of crystallization and form anhydrous substances.

4. Give Scientific Reason : Wood and glass are good insulators.

i.             When a current flows through a conductor, the free electrons in the atoms move from one end of the conductor to the other.

ii.           Certain materials have less free electrons in their atoms and the current does not easily flow through the material.

iii.          There are no such free electrons in wood and glass. Hence they cannot conduct electricity. Hence, they are good insulators.

5. Define

1. Electric motor: -

 A device which converts electrical energy into mechanical energy is called an electric motor.

2. Electric generator.

An electric device which converts mechanical energy into electric energy is called an electric generator.

 3. Attempt any 5 of the following. (15 Marks)

1. 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:

1.   The object is always placed on the left of the mirror.

2.   All distances parallel to principal axis are measured from the pole of the mirror.

3.   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.

4.   Distances measured perpendicular to and above the principal axis are taken as positive.

5.   Distances measured perpendicular to and below the principal axis are taken as negative.

6.   Focal length of convex mirror is positive while that of concave mirror is negative.

2. State any five Application of spherical mirror

                 i.    In torches and headlights: The source of light is placed at the focus to obtain a parallel beam of light.

               ii.    In flood lights: The source of light is placed just beyond the centre of curvature so as to get intense beam of light.

              iii.    Reflecting mirrors for projector lamps: The object is placed at the centre of curvature to obtain an image of the same size.

              iv.    To collect heat radiations in solar devices: Heat radiations from the sum coming from infinity are brought to focus by concave mirror in its focal plane.

                v.    Shaving mirror, dentist’s mirror: It produces an erect virtual and highly magnified image of an object placed between its pole and focus.

              vi.    Solar furnaces:  Large concave mirrors are used to concentrate sunlight to produce heat in solar furnace.

3.Write a note on Dispersion of light.

Ans.

1. The phenomenon of splitting of light into its component colours is dispersion of light.
2. The band of coloured components of a light beam is called it’s spectrum.
3. When White light is dispersed into seven colours by a prism, different colours of light bend through different angles with respect to incident ray.
4. Out of these seven colours, red light bend the least while violet light bends the most.
5. So the rays of each colour emerge along different paths and become distinct.
6. Hence we get a spectrum of seven different colours in the sequence, Violet, Indigo, Blue, Green, Yellow, Orange and Red.

4. pH scale (with proper diagram).

Ans.

i.             pH helps in measuring hydrogen ion concentration in solutions. In pH, p stands for “potenz” means “strength” in German.

ii.           The scale reads from O (zero) (most acidic) to 14 (most basic).

iii.          The value of pH indicates acidic or basic nature of a solution. The strength of base is represented by pOH.

iv.          When the pH value is in between 0 to 7, the solution is acidic in nature. At value 7, the solution is neutral and between 7 to 14 the nature of the solution becomes alkaline/ basic.

v.            Lower the pH of an acid, greater is the concentration of H+ ions, greater the pH of a base, greater is the concentration of OH ions.

5. In modern periodic table, which are the metals, non metals and metalloids among the first 20 elements?

Ans.  In the modern periodic table, among the first 20 elements, following are the metals, non – metals and metalloids.

Metals	Non  metals	Metalloids
Lithium (Li) Beryllium (Be) Sodium (Na) Magnesium (Mg) Aluminium (Al) Potassium (K) Calcium (Ca)	Hydrogen (H) Helium (He) Carbon (C)         Nitrogen (N) Oxygen (O)        Fluorine (F)          Neon (Ne) Phosphorus (P)   Sulphur (S)          Chlorine (Cl) Argon (Ar)	Boron (B) Silicon (Si)

6. Name

1.  Three elements having single electrons in their outermost shell. Ans.  Hydrogen, Lithium, Sodium, Potassium.

2.  Three elements with filled outermost shell.   Ans. Helium, Neon, Argon, Krypton, Xenon.

3.  Three elements having 7 electrons in their outermost shell. Ans. Fluorine, Chlorine, Bromine, Iodine.

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

1. What are the demerits of Mendeleev’s periodic table?

1.           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.

2.           Though isotopes of the same elements have different atomic masses, they cannot be placed separately in the periodic table. Since isotopes are chemically similar, they had to be given the same position in the periodic table.

3.           Some elements with higher atomic masses are placed before those having lower atomic masses, e.g. cobalt with atomic mass 58.93 is placed before nickel having atomic mass 58.71.

4.           Dissimilar elements were placed in the same group. E.g. Mn (Manganese) was placed in the group of halogens which totally differ in the properties.    

2. 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.  

Section B

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

1. The middle part of sperm possesses _______ which produce energy.

(mitochondria)

2. In _______ mode of reproduction the offsprings are with minor differences.

(asexual)

3. The organic compounds having double or triple bonds in them are termed as _______

(unsaturated hydrocarbons)

4.The digested food is absorbed by the _______ in the small intestine.

(villi)

5. Mercury and _______ are two metals in the liquid state at room temperature. ( gallium)

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

1. _________ is an ore of aluminium.

a. Cryolite

b. Bauxite

c. Haematite

d. Aluminium carbonate

2. Bronze in an alloy of ______

a. copper and tin

b. copper and iron

c. copper and zinc

d. copper and aluminium .

3. The reaction of ethene with bromine is ________

a. a substitution reaction.

b. an addition reaction.

c. an elimination reaction.

d. an oxidation reaction.

4. The unutilized carbohydrates are stored in the form of ________ in plants.

a. proteins

b. fats

c. glycogen

d. starch

5. The ____ provides general basic design of the body.

a. inheritance

b. father

c. mother

d. evolution.

6. Attempt the following. (10 Marks)

1. Write the salient features of the Biomedical Waste Rules.

Salient features of Biomedical waste rules are:

i.             These rules deal with the generation, handling, treatment and disposal of biomedical waste.

ii.           These rules apply to all persons who generate, collect, receive, store, transport, treat, dispose, or handle biomedical waste in any form.

iii.          It is duty of the occupant to take all steps to ensure that such waste is handled without any adverse effect to human health and environment.

iv.          These rules specify waste management procedures.

2. What major harm is done to the human beings by air pollution?

Air pollution can affect our health in many ways with both short term and long term effects.

i.             Short term effects include:

a.    Irritation of eyes, nose, mouth and throat.

b.    Respiratory infections such as bronchitis, pneumonia.

c.    Headaches, nausea and allergy.

d.   Asthma attacks

e.    Reduced lung functioning.

ii.           Short term effects include:

a.    Chronic pulmonary disease

b.    Lung cancer.

 3. Primary and Secondary pollutant.

Primary pollutant	Secondary Pollutant
Primary pollutants are the pollutants that are emitted directly from the sources and are found in the atmosphere in the form in which they were emitted. Examples: Ash, smoke, radioactive compounds, oxides of sulphur etc.	Secondary pollutants are the pollutants that are formed in the atmosphere by chemical reactions between primary pollutants and atmospheric constituents. Examples: SO3 m O3 , Ketones, Peroxyacetyl nitrate.

4. What are alkynes? Name the first member of alkyne family.

Ans. Hydrocarbons containing triple bonds between carbon atoms are alkynes. The first member of alkyne family is ethyne or acetylene

5. Explain the following terms:

a.    Hydrotropic movement: - The movement or growth of the root system of a plant in response to the stimulus of water is called hydrotropic movement.

b.    Chemical control in animals:  chemical control in animals is brought about by chemical substances called hormones. These hormones are secreted by the endocrine glands.

7. Attempt the any five following. (15 Marks)

1. Give scientific reason : Translocation is needed in all higher plants.

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

ii.           Higher plants bear roots, leaves, flowers, fruits and seeds. These part of plants need food for carrying out their various metabolic activities.

iii.          The amino acids, sugar and starch are stored in fruits and seeds for future use.

iv.          Thus, translocation is needed in higher plants.  

2. Write short notes on Functional group

1. The atom or group of atoms present in the molecule which determines characteristic property of organic compound is called the functional group.
2. All organic compounds are considered as derivatives of hydrocarbons, it is formed by replacing one or more hydrogen atom in a molecule by some other atom.
3. In methane CH₄, if one hydrogen is replaced by an –OH group, then compound methyl alcohol. CH₃.OH is formed. The –OH group is the alcoholic functional group.
4. After replacement, a new compound has functions i.e. properties different from the parent hydrocarbon.

3. Give scientific reason: Tarnished copper utensils are cleaned with lime juice or tamarind.

Ans.

i.             When copper utensils are exposed to moist air, they get tarnished or corroded due to the formation of green copper carbonate.

ii.           When these tarnished vessels are rubbed with lime juice or tamarind the weak acids present in them dissolve the green copper carbonate and original shine returns.

4 . What is an alloy? Give two examples with their chemical composition.

Ans. An alloy is a homogenous mixture of two or more metals or a metal and a non – metal in definite proportion.

Eg.

i.             Brass – copper and zinc.

ii.           Stainless steel – iron, nickel and chromium.

5. Write a note on  Catenation

1. The property of direct bonding between atoms of the same element to form chain is called catenation.
2. Carbon atoms possess an unusual capability of bonding to other carbon atoms.
3. Because of this feature, carbon atoms are capable of forming large number of compounds.
4. Carbon can link with other carbon atoms to form straight chains or branched chains or rings of different shapes and sizes.

6. The level of air pollution is very high in your locality.

The following measures can reduce air pollution in our locality:

i.            Plant trees on road sides and develop gardens, parks and open grounds in the locality.

ii.          A particular place can be provided for garbage collection and ensure that it is discarded daily.

iii.        Give awareness to the people about the use of non conventional source of energy like solar energy, wind energy etc. 

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

1. With the help of a diagram (Punnett square) show a Mendelian experiment where tall pea plant bearing red flowers is crossed with a short pea plant bearing white flowers. Write both the phenotypic and genotypic ratio for F2 generation.

i.             Tallness is the dominant character and the shortness is a recessive character. Similarly red colour of the flower is the dominant character and the white colour of the flower is the recessive character.

ii.           Thus the gene combinations responsible for the charcters mentioned in the question are as follows.

Tallness = TT      Shortness = tt     Red flowers = RR     White flowers = rr

1.    P generation = TTRR (Tall and red), ttrr (short and white)

Gametes of P₁ = TR X tr

F₁ generation : TtRr (Tall red)

2.    In F₁ generation all the plants will be with genotype TtRr and their phenotype will be tall red.

F₂ generation all the plants will be with genotype TtRr and their phenotype will be tall red.

F₂ generation  : Cross between TtRr X TrRr

	TR	Tr	tR	tr
TR	TTRR(Tall red)	TTRr (Tall red)	TtRR (Tall red)	TtRr (Tall red)
Tr	TTRr(Tall red)	TTrr(Tall white)	TtRr(Tall red)	Ttrr(Tall white)
tR	TtRR(Tall red)	TtRr(Tall red)	ttRR(Short Red)	ttRr(Short red)
tr	TtRr (Tall red)	Ttrr(Tall white)	ttRr(Short red)	ttrr(Short white)

In F₂ generation the ratio obtained will be 9:3:3:1 in the following proportion:

9 Tall red: 3 Tall white: 3 Short red: 1 Short white.

Therefore in the F₂ generation: Phenotypic ratio is 9:3:3:1

Genotypic ratio is 1: 1:2:2:4:2:2:1:1.

2. Co – ordination in plants.

       i.    Plants do not have a nervous system or muscular system and sense organs like eyes, ears, nose, etc.

     ii.    The plants can still sense the presence of stimuli like touch, light, gravity, water, etc., and respond to them by the action of hormones in them.

    iii.    So, plants co – ordinate their behaviors against environmental changes by using hormones.

    iv.    Hormones bring about various movement in response to stimulus.

      v.    It is the result of such co – ordination that the lotus opens in the morning and the tube rose at night; stem grow towards light and the root towards gravity; the leaflets of the mimosa plant close on being touched and the explosive fruit of balsam burst open to scatter the seeds.