EXAMINATION SCIENCE & TECHNOLOGY CLASS X (THEORY) 2007 MARCH,

Science & Technology
CLASS X (THEORY)
TIME : 2 ½ 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. The candidates are advised to attempt all the questions of Section A separately and section B separately.

3. All questions are compulsory.

4. There is no overall choice. However, internal choice has been provided in two questions of five marks category in Section A and one question of 2 marks category and one question of 3 marks category in section B. You are to attempt only one option in such questions.

5. Marks allocated to each question are indicated against it.

6. Questions 1 to 4 in Section A and 17, 18 in Section B are very short answer questions. These are to be answered in one word or one sentence only.

7. Questions 5 to 8 in Section A and 19, 20 in Section B are short answer questions. These are to be answered in about 30-40 words each.

8. Questions 9 to 14 in Section A and 21 to 23 in Section B are also short answer questions. These are to be answered in about 40 – 50 words each.

9. Questions 15, 16 in Section A and 24 in Section B are long answer questions. These are to be answered in about 70 words each.


Section A
1. Write the relation between 1 joule, 1 volt and 1 coulomb. [Marks 1]

2. Name the compound formed when gypsum is heated at 373 K in a kiln [Marks 1]

3. Identify the functional group present in propanone (CH3 CO CH3) [Marks 1]

4. Name the component of solar radiation, exposure to which can cause skin cancer [Marks 1]

5. Why does a ray of white light split up into different colours on passing through a glass prism? 
Name one example of this phenomenon in everyday life. [Marks 2]

6. a) Equilibrium constants for the two reactions are indicated against each other [Marks 2]
i) N2O4 (g) 2NO2 (g) K = 4.66 x 10-3

ii) 2NH3 (g) N2(g) +3H2 (g) K = 3.0 x10-9

In which of the above reactions will the product(s) be dominant species at equilibrium and why ?

b) Consider a general reaction
aA [Marks bB cC +dD
Write the expression for equilibrium constant for this reaction

7. Why does a goldsmith find it unsuitable to make ornaments of 24 carat gold ?
Name two elements, addition of any one of which to pure gold, makes it suitable for ornament making. [Marks 2]

8. Name the common source which powers both the wind energy as well as ocean thermal energy. Write one main advantage of using Ocean Thermal Energy conversion system. What is the essential characteristic of liquids used in Ocean thermal Energy Conversion systems ? [Marks 2]

9. Name the commercial unit of electric energy. Derive its relation with S.I unit of energy. State the relation used to calculate the electric energy consumed in a given time ‘t’ when a current I is flowing through a wire of resistance R. [Marks 3]

10. Identify the colourless gas, which has a choking smell, forms acid rain and is used for bleaching wood pulp in paper industry. Why this gas acts as a reducing agent only when it is moist? State the colour change you would observe when this gas is passed through acidified potassium dichromate solution. [Marks 3]

11. An electrician assembling a household circuit uses a long thick copper wire with green insulation and a short wire made of copper tin alloy. What are the two wires called? Mention the importance of each wire in an electrical circuit. How are the two wires connected in the circuit? [Marks 3]

12. a) Write the chemical formula of washing soda
b) What happens when the crystals of washing soda are left exposed to air ?
c) What colour change would you observe on adding
i) blue litmus solution to an aqueous solution of washing soda.
ii) red litmus solution to an aqueous solution of washing soda [Marks 3]

13. State two conditions necessary in the preparation of methanal from methanol.
Write balanced chemical equation for the reaction involved. What is the aqueous solution of methanol known as ? What is its use in the school laboratory ? On which property is this use based? [Marks 3]

14. What is a geostationary satellite ? Draw a labelled diagram to show the orbit of such a satellite. Write two applications of such a satellite. [Marks 3]

15. Identify the compound which exists as a colourless oily liquid, is dehydrating agent and is called the “King of chemicals”. What do you observe when this compound is added to 
(i) crystals of sugar 
(ii) crystals of copper 
(II) sulphate. Write balanced chemical equations to represent the reactions that take place in the manufacture of this compound . [Marks 5]

OR

Two organic compounds (X) and (Y) have the same molecular formula C3H6O2. Only compound (X) evolves carbon dioxide from sodium carbonate. Compound (Y) reacts with sodium hydroxide forming an alcohol and a salt of carboxylic acid.
a) Write the chemical formula of i) (X) and ii) (Y)
b) Name the functional group present in i) (X) and ii) (Y)
c) How can an alkane having two carbon atoms be formed from (X)? Write the chemical equation involved. [Marks 5]


16. For an object placed at a distance of 20 cm from the pole of a mirror, an image is formed 40 cm further away from the object on the same side
(a) What is the nature of the mirror?
(b) Is the image formed real or virtual?
(c) Draw a ray diagram to show the image formed
(d) Calculate the focal length of the mirror used. [Marks 5]

OR

An object is placed 12 cm away from the optical centre of a lens. Its image is formed exactly midway between the optical centre and the object
a) What is the nature of the lens?
b) Is the image formed erect or inverted?
c) Draw a ray diagram to show the image formed.
d) Calculate the focal length of the lens used.


SECTION – B
17. A student dipped the head part of a cockroach and a rat in water. After five minutes, he found that only one of the two animals survived. Which of the two
animals might have survived? [Marks 1]

18. UV rays are said to be harmful to human beings but we drink water from water filters in which such rays are used. Why is drinking this treated water not
harmful?. [Marks 1]

19. Name excretory units of kidney. State the vital functions of human kidney.2

20. How does development affect the environment? How can a balance be struck between the environment and development? Explain briefly. [Marks 2]

OR

What is green house effect? Name two green house gases.

21. Write the full form of IUCD. Name any one IUCD and describe its function. [Marks 3]

22. List four functions of blood. Why does blood look red? Which chamber of human heart receives oxygenated blood from lungs? [Marks 3]

OR

What is the need of special tissues or organs for transport of substances in plants and animals? Describe the transport of i) mineral and ii) food in plants.

23. What is meant by the term i) haploid and ii) diploid? How are chromosomes, DNA and genes related to each other? [Marks 3]

24. What is photosynthesis? Write overall equation of the reaction representing photosynthesis. Where does the light and dark reaction take place in the chloroplast? Explain the light reaction in the mechanism of photosynthesis? [Marks 5]