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1.1 INTRODUCTION:

Chemistry is defined as that branch of science which deals with the composition and properties of matter and the changes that matter undergone by various interactions. A chemical compound is formed as a result of a chemical change and in this process different type of energies such as heat, electrical energy, radiation etc. are either absorbed or evolved. The total mass of the substance remains the same throughout the chemical change.

1.2 CHEMICAL ACTION OR REACTION:

When a chemical change occurs, a chemical action is said to have taken place. A chemical change or chemical action is represented by a chemical equation. The matter undergoing change in known as reactant and new chemical component formed is known as product.

1.2 (a) Characteristics of a Chemical Reaction:

When we heat sugar crystals they melt and on further heating they give steamy vapour, leaving behind brownish black mass. On cooling no sugar crystals appears. Thus change which takes place on heating sugar is a chemical change and the process which brings about this chemical change is called chemical reaction.

• In this reaction the substance which take part in bringing about chemical change are called reactants.

• The substance which are produced as a result of chemical change are called products.

• These reactions involve braking and making of chemical bonds.

• Product(s) of the reaction is/are new substances with new name(s) and chemical formula.

• It is often difficult or impossible to reverse a chemical reaction.

• Properties of products formed during a chemical reaction are different from thos of the reactants.

• Apart from heat other forms of energies are light and electricity which are also used in carrying out chemical changes.

In all chemical reactions, the transformation from reactants to products is accompanied by various characteristics, which are-

(i) Evolution of gas : Some chemical reactions are characterized by evolution of a gas.

• When zinc metal is treated with dilute sulphuric acid, hydrogen gas is evolved. The hydrogen gas burns with a pop sound.

Zn (s) + H2SO4 (dilute) ZnSO4 (aq) + H2(g)

• When washing soda is treated with hydrochloric acid, it gives off colorless gas with lots of effervescence.

Na2CO3(s) + 2HCI 2NaCI (aq) + H2O(I) + CO2(g)

• 2NaNCO3 (s) Na2SO3 (s) + H2O + CO2 (g)

Sodium hydrogen Sodium carbonate Water Carbon dioxide

carbonate

important question paper science

PRE-BOARD EXAMINATION(II)

Class- X

Subject - Science

    Time : 2½ Hours                                                           Max. Marks : 60

 

General Instructions

1. The question paper comprises of two sections A and B. You are to attempt both

     the sections.

2. All questions are compulsory.

3. There is no overall choice However, internal choice has been provided in all the

     three questions of five marks category. Only one option in such questions is to be

     attempted.

4. All questions of section A and all questions of section B are to be attempted

    separately.

5. Questions 1 to 6 in section A and 17 to 19 in section B are short question. These

    carry one mark each.

6. Questions 7 to 10 in section A and 20 to 24 in section B are short answer type

    questions and carry two marks each.

7. Questions 11 to 14 in section A and 25 to 26 in section B are also short answer

     type questions and carry three marks each.

8. Questions 15 and 16 in section A and question 27 in section B are long answer

     type questions and carry five marks each.

 

SECTION A

1. If a mirror has a focal length of -25 cm, what will be its radius of curvature and nature? 1
2. Write chemical equations for reactions taking place when Manganese dioxide is heated with aluminium powder. 1
3. During summer season, a milkman usually adds a very small amount of baking soda to fresh milk. Give one reason. 1
4. What is the angle of reflection if a ray falls normally on a plane mirror? 1
5.  Can a displacement reaction be a redox reaction? Explain with example. 1
6. An electric geyser has the ratings 2000W, 220V marked on it. What should be the minimum rating, in whole number of a fuse wire, that may be required for safe use with this geyser? 1
7. A solution of a substance ‘X’ is used for testing CO_2­. Identify ‘X’. What will be its reaction with Carbon dioxide? Write balanced chemical equation for the reaction. 2
8. A student has been collecting silver coins and copper coins. One day she observed a black coating on silver coins and a green coating on copper coins. Which chemical phenomenon is responsible for these coatings? Write the chemical name of black and green coatings. 2
9. Differentiate between short circuiting and overloading of electrical circuits. How does a fuse protects an electrical circuit? 2
10. Draw the pattern of magnetic field lines of a current carrying solenoid. What does the pattern of field lines inside the solenoid indicate? Write one application of magnetic field of current carrying solenoid. 2
11. A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet:

     (a) pushed into the coil  

     (b) withdrawn from inside the coil 

     (c)  held stationary inside the coil. 3

12. Two compounds ‘A’ and ‘B’ have the same molecular formula C4H8O2. Compound ‘A’ is an acid and compound ‘B’ has a fruity smell. Suggest (i) chemical formulae and (ii) the structural formulae of compounds A and B. Name the functional group of compound B. What name would you give to the relationship between the compounds A and B.  3
13. (a) Two lenses have power of (i) + 2D (ii) - 4D. What is the nature and focal length of each lens.?

          (b) An object is kept at a distance of 100cm from each of above lenses.

          Calculate the (i) image distance (ii) magnification in each of the two cases. 3

14. Two elements X and Y belong to groups 1 and 2 respectively in the same period. Compare them with respect to

          (a) the number of valence electrons

          (b) valency

          (c) metallic character

          (d) size of the atoms.

          (e) formulae of their oxides and chlorides. 3

15. (a) C₂H₆O is formula of second member of homologous series of alcohol. Give formula of fourth member.

     (b)The molecular formula of an organic compound is C₃H₆O. Write the formula and names of aldehydes and ketones which are represented by this formula.

     (c) What are structural isomers? Give all structural isomers of C₄H_10.

          OR

(a) Why does carbon form largest number of compounds?

(b) Why are some of these called saturated and other unsaturated compounds?

(c) Which of these two is more reactive and Why?

(d) Write the name and structure of two saturated and two unsaturated  compounds. 5

16. In a household electric circuit different appliances are connected in parallel to one another.

          Give two reasons.

          An electrician puts a fuse of rating 5A in that part of domestic electrical circuit       in which an electrical heater of rating 1.5kW, 220V is operating. What is likely   to happen in this case and why? What change, if any, needs to be made?

          OR

You are given following current-time graphs from two different sources:

(i) Name the type of current in two cases.

(ii) Identify any one source for each type of these currents.

(iii) What is the frequency of current in case II in India?

(iv) Use above graphs to write two difference between the current in two cases. 5

SECTION B

17. What happens at the synapse between two neurons? 1
18. The human hand, cat paw and the horse foot, when studied in detail show the same structure of bones and point towards a common origin.

          (i) What do you conclude from this?

          (ii) What is the term given to such structures? 1

19. Name two gases, other than carbon-di-oxide, that are given out during burning of fossil fuel and contribute towards acid rain formation. 1
20. How did the ‘Chipko andolan’ ultimately benefit the local population? Give any two benefits.  2
21. Explain the Sex determination in Human. 2
22. Name those parts of the flower which serve the same function as the following do in the animals:-

          (i) testis (ii) ovary (iii) eggs (iv) sperms. 2

23. Study carefully the food chains given below:-

          Food chain I : grass - grasshopper - frog

          Food chain II : wheat - rat - snake - hawk

          To which of the two consumers, snake or hawk will more energy (percent) be available and why? 2

24. What do the following transport?

          (i) xylem (ii) phloem (iii) pulmonary vein (iv) Vena Cava. 2

25. The genotype of green stemmed tomato plants is denoted as GG and that of purple stemmed tomato plants as gg. When these two are crossed,

          (i) What colour of stem would you expect in their F1 progeny?

          (ii) Give the percentage of purple-stemmed plants if F1 plants are self   pollinated.

          (iii) In what ratio would you find the genotypes GG and Gg in the F2 progeny?3

26. Why are environmentalists insisting upon ‘sustainable natural resource management’? Give any three reasons. 3
27. (i) Draw the diagram of heart and label its four chambers

          (ii) Construct a table to show the functions of these four chambers. 5

          OR

          Plants absorb water from the soil. How does this water reach the tree tops?    Explain in detail.

papers sst

TIME-3 HOUR                                                                            MAX.MARKS-80

Instructions :

Q1.      Who were Nattukottai Chettiars?                                                                                   

                                                                        OR

What was the role of gomastha under the East India Company?

OR

What was referred to as the ‘iron monster’ in London?

Q.2      Why was Vernacular Press Act passed in the year 1878?                                          1

OR

Mention the main theme of ‘Oliver Twist’ written by Charles Dickens.

Q.3      Define a Patriarchal society.                                                                                              1

Q.4      Describe the position of women in the field of central and state legislature.                       1

Q.5      According to IUCN, define endemic species.                                                                 1

Q.6      In which two states of India Himalayan Yew is found?                                                            1

Q.7      Give one main reason for low infant mortality rate in Kerala.                                      1 

Q.8      State one reason behind tertiary sector becoming so important in India.                  1

Q.9      Mention any one inconvenience in barter system.                                                       1

Q.10    What is the meaning of liberalization?                                                                            1                          

Q.11    Describe any three significance of Salt march by Gandhiji.                                        3x1=3

Q.12    Describe any three impacts of the Non-cooperation movement over the towns and countryside in India.                                                                                                              3

Q13     Examine any two factors of the Economic Depression of 1929. What were its effects on USA?                                                                                                                                     2+1=3

Q.14    Read the following extract taken from the textbook and answer the questions that follow:

In 1926, Begum Rokeya Sakhawat Hossien, a noted educationist and literary figure.

strongly condemned men for withholding education from women in the name of religion

as she addressed the Bengal Women’s Education Conference:

The opponents of female education say that women will become unruly.....Fie! they call

themselves Muslims and yet go against the basic tenets of Islam which gives women an

equal right to education. If men are not led astray once educated, why should women?

(a) Explain how Begum Rokeya Sakhawat Hossein asserts  women’s right to education?

(b) What was the impact of printed books on women in India in the 19th century.?1+2=3

OR

Read the following passage and answer the questions given below it :                              2+1=3

‘Dear children, don’t read these novels, don’t even touch them. Your life will be ruined. You will suffer disease and ailments. Why did the good Lord make you - to wither away at a tender age? To suffer in disease? To be despised by your brothers, relatives and those around you? No. No. You must become mothers; you must lead happy lives; this is the divine purpose. You, who were born to fulfill this sublime goal, should you ruin your life by going crazy after despicable novels?’

(a) Analyse the message given by the writer to children.

(b) Name the woman novelist of early nineteenth century who wrote against traditional                 role of women as wives and mothers.

Q.15    Why the power sharing is desirable? Describe with examples. Mention the            prudential & moral cause for power sharing.                                                                 1+2

Q.16    What is democratic decentralization? Write any four major steps taken by the government in 1992 for the growth of Democratic decentralization in India.                        1+2=3

Q.17    Mawsynram is the region of highest rainfall, yet it faces acute shortage of water. Why?3

Q.18    Compare India and Nepal on the basis of any three indicators of Human Development Index for 2004.                                                                                                                           3                                              

Q.19    In Britain the formation of the nation state was not the result of a sudden upheaval or revolution. It was the result of a long-drawn-out process. Explain.                           4

Q.20    What are overlapping & cross-cutting differences? Describe with examples.          2+2=4

Q.21    Describe the types of political parties & their formation.                                              2+2=4

Q.22    Why is democracy better than dictatorship? Describe with examples how democracy is a form of government, which is accountable, responsive & legitimate.              1+3

Q.23    Compare the diagrams showing land use pattern of India and answer the questions that follow:                                                                                                                            2+2

i)             Name the two categories under which the area in use has increased. Give at least one reason for this increase.

ii)            Name the two categories under which the area in use has decreased. Give at least one reason for this decrease.

Q.24          The growth rate in Agriculture is decelerating, which is an alarming situation. Explain.                                                                                                          4

Q.25          How are the activities in the economy classified on the basis of  employment conditions? Explain.                                                                                             4

Q.26          What is the basic idea behind the SHGs for the poor? Explain in your own words.                                                                                                                                               4

Q.28          Why is ‘tax’ on imports known as trade barriers? Why did the Indian Government impose barriers to foreign trade and foreign investments after Independence? Give three reasons.                                                                                             1+3

Q.29    Six features with serial nos. 1 to 6 are marked on the given outline political map of India

Identify these features with the help of the following information and write their correct names on the lines marked in the map :                                                                                1X6

1.         A city associated with Jallianwalan Bagh incident.

2.         Place where the session of Indian National Congress was held in 1927

3.         A type of soil

4.         A major tea producing state.

5.         An iron ore mine.

6.         An oil field.

OR

Locate and label the following on the given outline political map of India.

1.         A place where session of Indian National Congress was held in September1920;

2.         A place where Gandhi started satyagraha against Indigo planters.

3.         A dam built on river Chenab.

4.         An iron ore mine in Karnataka.

5.         A natural gas field in Gujarat.

6.         A thermal power plant in Tamilnadu.