CBSE Guess Paper class X 2008 science 1


Roll.No. Code.No. 086/1

  • Please check that this question paper contains 4 printed pages
  • Code number given on the right hand side of the question paper should be written on the title page of the answer book by the candidates.
  • Please check that this question paper contains 24 questions.
  • Please write down the serial number of the question before attempting it.

SCIENCE (THEORY)

Time allowed: 2½ hours ] [Maximum Marks: 60

General Instructions:

  1. The question paper comprises 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 some questions.You are to attempt only one option in such questions.
  5. Marks allocated to every question are indicated against it.
  6. Question numbers 1—4 in Section A and 17— 18 in Section B are very short answer questions and are of 1 mark each. These are to be answered in one word or one sentence each.
  7. Question numbers 5—8 in Section A and 19— 20 in Section B are short answer questions and are of 2 marks each. These are to be answered in 30—40 words each.
  8. Question numbers 9—14 in Section A and 21—23 in Section B are also short answer questions and are of 3 marks each. These are to be answered in 40—50 words each.
  9. Question numbers 15—16 in Section A and 24 in Section B are long answer questions and are of 5 marks each. These are to be answered in 70 words each.

SECTION - A

1. a. Is magnetic field a scalar or a vector?

b. Draw the magnetic field lines in and around a bar magnet 1

2. Write the chemical formula of Plaster of Paris. Why is it stored in water–proof containers? 1

3. Why are copper and aluminium wires usually employed for electricity transmission? 1

OR

What is the use of a variable resistance? Give an example of such a device. 1

4. Antioxidants are added to foods containing fats and oils. Give reason. 1

5. A gas X when passed through lime water turned it milky.

(i) Identify X and write the necessary chemical equation. 1

(ii) What happens if excess of this gas is passed into lime water? 1

6. State Right hand thumb rule. What is it used for? 2

7. What happens when :

(i) Lead nitrate is heated

(ii) Silver chloride is kept outside during daytime.

Also write the necessary chemical equations. 2

8. Define potential difference. Give its S.I. unit. Name the instrument used to measure potential difference between 2 points in an electric circuit. 2

9. What is the difference between displacement and double displacement reactions? Write equations for each. 3

10. Give reasons for the following: 3

(i) Household appliances are connected in parallel systems.

(ii) Metallic parts of electric irons and toasters are connected to earth wire

(iii) Fuse wire is connected in series with electrical devices.

11. a. What does pH of a solution indicate? 1

b. Complete the following chemical reactions : 2

(i) Na2CO3 + HCl

(ii) Cu2O + HCl

12. A parallel combination of three resistances take a current of 7.5 A from a 30 V battery. If two of the resistance values are 10 Ω and 12 Ω, find the third. 3

13. a. Give 2 uses of sodium hydrogen carbonate. 1

b. Name the compound obtained by heating it. Is it an acidic or basic salt? 1

c. Write the chemical equation for the above process. 1

14. When will the force experienced by a current carrying conductor be maximum? State the rule used to calculate the same. 3

15. (i) Explain the working principle of an electric motor with a neat diagram. 3

(ii) What are the modifications made to the basic structure when motors are used for commercial purposes? 2

16. a. Which gas is formed when an acid reacts with a metal? How do you test for the presence of this gas? 2

b. How is the concentration of hydroxide ions affected when the following is added to NaOH solution?

(i) excess NaOH

(ii) distilled water

(iii) HCl solution

c. Why do acids not show acidic behaviour in absence of water?

SECTION B

17. Name the cells which control the opening and closing of stomata in plants. 1

18. Define translocation. Name the tissue which aids this process. 1

19. Compare aerobic and anaerobic respiration. 2

20. Distinguish between arteries and veins 2

21. (a) Which chamber of heart pumps blood into lungs? Why? 2

(b) How do unicellular organisms dispose off their waste materials? 1

22. How does food get digested in the longest part of our digestive system? Clearly explain the role of each enzyme secreted into this part. 3

23. How are water and minerals transported in plants? 3

24. (a) Draw a neat labeled diagram of the excretory system of human beings. 3

(b) What are the functions performed by :

(i) ureter 1

(ii) urinary bladder 1

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