E-cikai
Past Papers Solutions
SEE Science
2075 Province-7(Sudurpaschim)

Weight(w) of an object at any point is given by product of mass(m) and acceleration due to gravity(g) at that point.

b.  State Archimedes' principle.

Archimedes' principle states that weight of fluid displaced by an object immersed partially of fully in it is equal to the upthrust experienced by the object.

c. What is geothermal energy?

The heat energy stored below the earth's surface is called geothermal energy.  

d. Write the formula of power of a lens.

Power of a lens is defined as its ability to converge or diverge a parallel beam of light falling on it.

Mathematically, power(P) of lens is given by reciprocal of its focal length(f).
i.e. P = 1/f 

e. What is step up transformer?

The transformer which converts low voltage level to high voltage level is called a step up transformer.

f. Write the name of any two metalloids.

Examples of metalloids are as follows:-

g.  Write two examples of weak acids.

Weak acids are generally organic acids.

• Carbonic acid (H₂CO₃), 
• Methanoic acid also called formic acid (HCOOH), 
• Ethanoic acid also called acetic acid or vinegar (CH₃COOH), 
• Propanoic acid (C₂H₅COOH) etc

h. Write the atomic number and atomic weight of copper.

Atomic number of copper is 29 and its atomic weight is 63.546 amu.

i. What is concrete?

Concrete is mixture of cement, sand, gravel or crushed stone and water.

j.  Give two examples of exocrine gland.

Digestive gland, lacrimal gland, mammary gland, salivary gland, sweat gland are examples of exocrine gland.

k. What is vein?

The blood vessel which bring the blood into the heart from the different parts of the body is called vein.

l. What is the main function of sex chromosome?

Sex chromosome determines the sex of the offspring.

m. Name any two animals which have external fertilization.

Fish and frog have external fertilization.

Other animals that reproduce through external fertilizations are:-
Crab
Shrimp
Mollusks
Echinoderms

n. What is water pollution?

According to national institute of environmental health sciences water pollution is any contamination of water with chemicals or other foreign substances that are detrimental to human, plant or animal health.

o. What is carbonization?

Carbonization is the process of conversing woods into charcoal.








2.

Clarify the statement, "Acceleration due to gravity of the earth is 9.8 m/s²"

Acceleration due to gravity of the earth is 9.8 m/s² means a body falling solely under the influence of earth's gravity increases its speed by 9.8 m/s every second or a body moving upward solely under the influence of earth's gravity decreases its speed by 9.8 m/s every second.

Acceleration due to gravity of the earth is 9.8 m/s² means a body falling toward the earth surface in vacuum attains acceleration of 9.8 m/s².

Acceleration due to gravity of the earth is 9.8 m/s² means if a body irrespective of its mass allowed to fall freely such that it experiences no atmospheric resistance as in vacuum, the earth's gravity accelerates that body with magnitude of 9.8 m/s² toward its center or If a body irrespective of its mass allowed to move upward freely such that it experiences no atmospheric resistance as in vacuum, the earth's gravity decelerates that body with magnitude of 9.8 m/s² directed away from its center.




3.

Energy crisis cannot be solved immediately but it can be pushed up to the next generation. Give reason.

About 85% of global energy is fulfilled from coal, natural gas and oil and remaining 15% are obtained from renewable sources like hydropower, nuclear energy and other alternative sources of energy. Also energy demand is rapidly increasing annually. To prevent energy crisis human race should completely rely on sustainable energy resources. this can't be achieved immediately. But we can push energy crisis to the next generation by adopting following measures:-

(i)    By increasing the production of renewable energy,

(ii)   By finding new sources of renewable energy
(iii)  By using energy wisely and saving energy.

(iv)   By Innovating energy efficient technology



4.

Write any two importance of atmospheric pressure.

Importances of atmospheric pressure are as follows:-

(i)  Prevents bleeding :- Blood pressure of animals are around atmospheric pressure. Any substantial difference between animals' blood pressure and atmospheric pressure leads to bleeding.

(ii)  Prevents evaporation of liquid at normal temperature :- At very low pressure liquid around us will spontaneously change into gaseous state at normal temperature. For instance, water will no more be found in liquid state at 37ºC around 40 mm of Hg. At this condition liquid water turns into vapour.

(iii) Supports existence of life on earth :- Life would not exist without air. But air in not only sufficient. Proper atmospheric pressure is also required. Animals' blood circulation pressure is maintained by atmospheric pressure, life of aquatic animals is impossible without water and atmospheric pressure prevents water from turning into vapour.

(iv) Cooking :- By utilizing property of atmospheric pressure food can be cooked at lower temperature. 

This saves energy required for cooking.

Reduces loss of essential nutrients.

5.

10 kg of water at 80ºC cools faster than 15 kg of water at the same temperature kept in the identical vessels. Why?

10 kg of water have to lose less heat to get cooled at lower temperature compared to 15 kg of water. Also lower amount of heat is lost faster that is why 10 kg of water at 80ºC cools faster than 15 kg of water at the same temperature kept in the identical vessels.



Initial temperature of water in both vessels, T₀ = 80ºC
After cooling, let temperature declines to T₁
So, change in temperature, dT = (T₀ - T₁)
Heat lost by water is given by, Q = m.s.dT
Here s and dT are fixed so heat lost is directly proportional to the mass of water. 
i.e.  Q ∝ m
As 15 kg > 10 kg
So 15 kg of water have to lose more than 10 kg of water to decline to temperature T₁ from temperature T₀.
As both vessels are identical, rate of heat lost is also identical.
dQ / dT is same for water kept in both vessels.
10 kg of water loses heat faster to reach temperature T₁ than 15 kg of water. that is why, 10 kg of water at 80ºC cools faster than 15 kg of water at the same temperature kept in the identical vessels.
        


6.

Write two characteristics of 's' block elements.

Characteristics of s-block elements are as follows:-

(i)    Valence electrons are in s-orbitals.
(ii)   Number of valence electrons are either 1 or 2.
(iii)   They are electropositive elements that means they lose electron to form cations.
(iv)   Their chemical reactivity increases while going downward in a group.
(v)    Their atomic size increases while going downward in a group.
(vi)   Their melting point and boiling point decrease while going downward in a group.
(vii)  They are soluble in water. 
(viii) Their oxides are alkaline.
(ix)   They are metals.



7.

The state of chemical reaction increases with the increase of the surface area of reactant. Why?

This is so because more the surface area of the reactants more amount of reactants come in contact to each others at a time and increases the speed of chemical reaction.


8.

Write structural formula and one use of trihydric alcohol.

A trihydric alcohol has three hydroxyl groups (OH) in its molecular structure. Glycerol is the simplest trihydric alcohol. Its structural formula is shown below:-

Structural formula of Glycerol

Glycerol is used in food, personal care, pharmaceutical and explosive industries.

Uses of glycerol are as follows:-

(i)  As a moisturizing agent :- Glycerine, a mixture of glycerol with water, is used in cosmetic and personal care product as a moisturizer.

(ii)  As a sweetening agent (sugar alcohol) :-  Glycerol can be used as a sugar alcohol in items like food and medicine to add sweet taste to it. Glycerol tastes sweet and has low calorie as compared to sucrose (Table sugar C₁₂H₂₂O₁₁). Glycerol does not decay teeth as sucrose sugar does.

(iii) As a purgative (Laxative) :- Glycerol helps in easy evacuation of bowels for people suffering from constipation.

(iv) As a biodegradable solvent :- Glycerol can be used as a solvent to dissolve various materials which are even insoluble in water. Not only that, it is recyclable and biodegradable like water.

(v)  As a thickening agent :- Glycerol is a high viscous liquid and also non-toxic. So various liquors are mixed with glycerol to increase their viscosity. Beside this it also add sweet taste to liquors.

(vi) Glycerol is used as a ingredient in manufacture of various explosives.

(vii) Glycerol is a major ingredient in various cough syrup.



9.

Write any two differences between thermoplastic and thermosetting plastic.

Differences between thermoplastic and thermosetting plastic are as follows:-






10.

Write any two differences between drone and worker bee.

Differences between drone bee and worker bee are as follows:- 

Drone bee Vs worker bee

11.

Write any two effects that are seen due to lack of thyroxine hormone.

As per medlineplus.gov effects that are seen due to lack of thyroxine hormone are as follows:-

(i)    Constipation 
(ii)   Depression
(iii)  Dry skin 
(iv)  Fatigue
(v)   Fertility problems in women
(vi)  Goiter
(vii) Hair loss
(viii) Irregular menstrual periods
(ix)  Low tolerance for cold temperatures
(x)   Weight gain



12.

Write any two symptoms of hemophilia disease.

Symptoms of hemophilia disease are as follows:-
(i) Excessive bleeding
(ii) Easy bruisings.

Bruises on skin surface

13.

Write any two advantages of vegetative propagation.

Advantages of vegetative propagation are as follows:-

(a) Vegetative propagation allows plants to reach the mature phase faster.

(b) Desirable traits can be grown and yielded indefinitely as new plants are clones(Clone: Xerox, Photocopy) of their parent plant.

(c) It is suitable for growing plants having longer seed dormancy i.e. bear seeds after very long time.

(d) It is suitable for growing plants which do not bear seeds at all.



14.

Comet is seen after a long period of time. Why?

A comet is seen only when it comes closer to the sun. Due to sun heat comet's frozen part changes into gaseous atmosphere and seems like a bright tail. And revolution of a comet around the sun takes very long period. For some comets it is around 30 years while for some comets it is more than 30 million (30,000,000) years. That is why a comet is seen after a long period of time.







(Group 'C')                                                                                                      6x3=18



15.

How much time does a stone take to reach on the surface of the earth drop from the height 20 m and what will be its acceleration due to gravity after 3 seconds. (g = 10 m/s²)

Solution
Initial velocity, u = 0 m/s
Distance covered, S = 20 m
Acceleration due to gravity, g = 10 m/s²

From the formula,
S = ut + ½gt²  
20 m = 0.t + ½.10m/s².t²
20 m = 5t² m/s²
4s² = t²
(2s)² = t²
∴ t = 2s
Hence, the time taken by the stone at 20 m height to reach the surface is 2 seconds.

As it only takes 2 seconds to reach the surface after that stone comes in rest. Hence acceleration due to gravity after 3 seconds will be 0 m/s². 


16.

In a transformer the number of turns in primary coil is three times than the number of turns in secondary coil. If the primary voltage of transformer is 220 volt, find the secondary voltage.

Solution
Let number of primary turns be Np
Number of secondary turns be Ns
Given,
The number of turns in primary coil is three times than the number of turns in secondary coil
i.e. Np = 3Ns
So, Np/Ns = 3            ...............(i)

Primary voltage of the transformer, Vp = 220V
Let secondary voltage of the transformer be Vs.
 We have,
Np/Ns = Vp/Vs
3 = 220V/Vs
Vs = 220/3 V
∴Vs = 73.33 V
Hence, the secondary voltage is found to be 73.33 Volts.


17.

How does the ammonia gas is manufactured on industrial scale? Write with balanced chemical equation.

Ammonia gas is manufactured on industrial scale by Haber's process. In this process hydrogen gas (H₂) and nitrogen gas (N₂) is mixed in the ratio of 3:1 in the presence of finely crushed iron(Fe) as a catalyst at a temperature of 450ºC and 200 atmospheric pressure. To make iron a more efficient catalyst Molybdenum(Mo) is used as promoter.

3H₂ + N₂  ⇋  2NH₃ + Heat






18.

Write any three uses of aluminium.

Uses of aluminium are as follows:-

(i)  Making aircraft parts.

(ii)  Electrical transmission line wires are made up of aluminium.

(iii)  Aluminium as a heat sink:-  Aluminium alloys are used as heat sink in electronic devices.

(iv) Energy efficient cookwares :- Aluminium has higher thermal conductivity than iron and steel. It conduct heat more efficiently that steel cookwares. That is why cookwares which runs on electricity are made up of aluminium.

(v) Aluminium foils are used for packing of food item, tablets and many more. It prevent enclosed items from external air and light exposure.

(vi) Aluminium as a reducing agent:-  Metallic aluminium is a strong reducing agent with a standard reduction potential Eº = -1.662 V.

(vii)  As a catalyst:- Aluminium trichloride (AlCl₃) is used as a catalyst in Friedel-crafts reaction.

(viii) Mobile phone frame and casing:- Due to light weight and silvery look alloys of aluminium are used for making mobile phone frames and casing.


19.

Pea plant with red flower (RR) and white flower (rr) are crossed pollinated firstly and then self pollinated. What will be the colour of flower at first and second generation ? Why ? Write with necessary chart.

The chart is drawn as below:-





The colour of the flower at first generation is red because red colour of flower is dominant over white colour of flower. The colour of flower at second generation is both red and white in the ratio of 3:1. This is so because as per second law of Mendel both red and white gametes get separated during gametes formation.

Answer described in details:-

The colour of the flower at first generation is red although they are genotypically hybrid. This is so because as per first law of mendel dominant character is only able to express itself phenotypically while recessive character remains hidden and in case of pea red colour of flower is dominant character while white colour of flower is a recessive character.

And in second generation after self pollination of hybrid red flower the colour of flower produced is both red and white. The colour of red to white colour is 3:1. The reason behind this is verified by second law of mendel. As per this law the red and white gametes of the flower get separated during the formation of gametes. The fusion between red and red produce pure red flower while the fusion between red and white flower produce hybrid flower (phenotypically red but genotypically red and white) while the fusion between white and white flower produce pure white flower. 



20.  

Draw the diagram of larval stage of silkworm and label the parts thoracic true legs, spiracles, abdominal pseudo legs and dorsal horn.

(Group 'D')                                                                                                   4x4=16



21.

Draw a ray diagram of an image formed when an object is placed at a distance of 20 cm from a convex lens having focal length 20 cm. Write any two natures of image formed. Calculate the magnification of image.

The ray diagram for above given problem is drawn below:-





Natures of the image :-
(i) Real 
(ii) Inverted

See this video better illustration




Magnification of the image:-
Object distance, u = 20 cm
Image distance, v = ∞
Magnification, m = v/u = ∞/20 = ∞
The image formed is infinitely magnified.



22.

Study the given diagram and answer the following questions.

i) Which gas is collected in gas jar?

ii) This gas cannot be collected by downward displacement of water. Why?

iii) How can you manufacture urea from the gas collected in gas jar? Write with balanced chemical equation.

(i)  Carbondioxide (CO₂) gas is collected in the jar.

(ii)  Carbondioxide cannot be collected by downward displacement of water because it is soluble in water.

(iii)  Carbondioxide is reacted with ammonia under high pressure and temperature to form ammonium carbamate (NH₂CO₂NH₄). This ammonium carbamate is dehydrated to form urea(NH₂CONH₂).

2NH₃ + CO₂ → NH₂CO₂NH₄

NH₂CO₂NH₄ → NH₂CONH₂ + H₂O

23.

How does blood play an important role in the context of control and protection? Suggest any two precautions to be taken to reduce the high blood pressure.

In context of control blood regulates our body temperature and the pH value.
And in context of protection blood does the following tasks:-

(i)  Blood clotting
(ii) Immunological function to fight against foreign bodies.

Precautions to be taken to reduce the high blood pressure are as follows:-

(i)   Healthy diet
(ii)  Maintain proper weight
(iii) Regular physical exercise
(iv) Avoid active as well as passive smoking
(v)  Avoid alcohol consumption
(vi) Proper rest and sleep.


24.  

How do industrial gases cause acid rain? Explain with chemical reaction. Mention the effects of industrial gases.

Oxides of carbon, nitrogen and sulphur are produced by industries are industrial gases. The oxides of carbon, nitrogen and sulphur present in the atmosphere reacts with rain droplets and form acid and as a result acid rain occurs.


4NO₂ + 2H₂O + O₂ → 4HNO₃ (Nitric acid)

SO₃ + H₂O → H₂SO₄ (Sulphuric acid)

SO₂ + H₂O → H₂SO₃ (Sulphurous acid)


Effects of industrial gases are as follows:-

(i)  Industrial gases are also greenhouse gases. So these gases contribute to climate change.

(ii)  Acid rain

(iii)  Adverse effect to human health.

(iv)  Obscuration in atmospheric visibility.