Exam Papers — 29 February 2012

1. If one views one’s face in the bulged out shining surface of big spoon, will the image be smaller or longer? Why?

2. Why is the conversion of ethanol to ethanoic acid an oxidation reaction?

3. Give two examples where sex determination is regulated by environmental factors.

Or

If a trait ‘A’ exists in 10% of a population of an asexually reproducing specious and a trait ‘B’ exists in 6% of the same population, which trait is likely to have arisen earlier?

4. Identify which one of the following would have a hazardous impact if they persist in the environment for a long time:

Newspaper, Vegetable Peels, Pesticides, Waste from cattle shed.

5. Where should an object be placed in front of a spherical mirror of focal length 24 cm to obtain its image, double the size of object?

6. What is power of accommodation of eye? How does ciliary muscles control the power of accommodation?

7. Why does sky appear blue? Why does the sky appear dark to an astronaut?

8. How do you think the tendency to lose electrons will change in a group?

9. Why first group elements of modern periodic table are called an alkali metals? Give one example with reaction.

10. Why are traits acquired during the life time of an individual not inherited?

11. Name those parts of the flower which serve the same function as the following do in the animals.

(a) Testis (b) Ovary (c) eggs (d) sperms

12. Give reasons for the following:

(a) Food chains consist of maximum four to five topic levels.

(b) Among the ozone depleting substances, chlorofluro carbon (CFC) are the most harmful

13. How can you distinguish between a plane mirror, concave mirror and a convex mirror with out touching them?

If you are driving a car, what type of mirror would you prefer to use for observing traffic at your back and why?

14. An object is place 12m away from a combination of concave and convex lenses having their powers 1.25 D and 1.50 D respectively. What is the nature of image formed?

15. With the help of a diagram show how Hypermetropia is corrected. What is the power of the lens required to correct the Hypermetropic defect of a person whose near point is 1 m.

16. Give reasons for the following observations:

(i) The element carbon forms a very large number of compounds.

(ii) Air holes of a gas burner have to be adjusted when the heated vessels get blackened by the flame.

(iii) Use of synthetic detergents causes pollution of water.

17. (A) what were the two achievements of Mendeleev’s periodic table? What was the basis of classification of element in it?

(b) Would you place the two isotopes of chlorine, Cl-35 & Cl-37 in different slots because of their different atomic masses or in the same slot because their chemical properties are the same? Justify your answer.

18. Suggest any four changes that you would like to be incorporated in the life style of students of your age so move towards a sustainable use of available resources.

19. The genotype of green stemmed tomato plants are denoted as GG and that of purple stemmed tomato 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 FF and gg in the F2 progeny?

20. (i) What could be the reasons for adopting contraceptive Methods?

(ii) Describe any two methods of birth control.

21. (i) What is the importance of DNA copying in reproduction?

(ii) The sex of the new born child depends on its father and not on its mother. Justify the statement and support your answer with neat illustration.

22. What is fertilization? Explain double fertilization in an angiosperm plant.

23. (a) What type of mirror should be used to get a real image?

(b) Draw a labeled ray diagram to show the formation of image by a concave mirror if object is placed between pole and focus of the mirror

Or

(a) Define principal focus of an convex lens

(b) Copy the diagram on your answer sheet, with proper scale and complete it

24. (a) An organic acid ‘X’ is a liquid which often freezes during winter time in cold countries, has the molecular formula C2H4O2. On warming it with ethanol in the presence of few drops of concentrated sulphuric acid, compound ‘Y’ with a sweet smell is formed.

(i) Identify ‘X’ & ‘Y’

(ii) Write a chemical equation for the reaction involved.

(b) What would be observed on adding a 5% solution of alkaline potassium permanganate solution drop by drop to some warm ethanol taken in a test tube?

25. (i) If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases?

(ii) Write the secondary sexual characters in males and in females.

(iii) What is vegetative propagation? State two reasons of practicing vegetative propagation for giving same types of plants.

ALL THE BEST FOR YOUR EXAMS!!!

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