Friday, March 8, 2013

8th Science [CBSE Practice Paper-2]

[Practice Paper]
LESSON-7 (Combustion and Flame) 
LESSON-9(Crop Production and its Management)
LESSON-20 (Pollution of water)

2 marks Questions :-

Q1 What is a fuel? Give examples

Q2 What are combustible materials?

Q3 When we boil water in paper cup, the cup does not catch fire. Why?

Q4 Define ignition temperature. What is the ignition temperature of White Phosphorus?

Q5 What happens when a matchstick is striked against the matchbox?

Q6 Flame of a burning candle goes off, when we blow over it strongly. Give suitable reason.

Q7 Differentiate between Rapid and Spontaneous Combustion.

Q8 Why does a small piece of Sodium or White Phosphorus catch fire in air?

Q9 What precautions should be taken at LPG godowns or petrol pumps?

Q10 If a person’s cloth catches fire, how can you put it off?

Q11 What are the harmful effects of incomplete combustion?

Q12 How is acid rain harmful?

Q13 Define Explosive Combustion with examples.

Q14. (a)What are the advantages of using manure?

(b)Why is overuse of fertilizers not recommended?

Q15. Differentiate between autotrophs and heterotrophs?

Q16. How does man became the food producer from a food gatherer?

Q17. Define crop production and sowing.

Q18. “Agriculture practices have undergone lot of changes” Justify the statement.

Q19. What are crumbs? How are they crushed?

Q20. What will happen when farmers continue to grow the same crop in the same field?

Q21. Differentiate between agriculture and agriculture practices?

Q22. How is manure formed by the farmers?

Q.23. Define water pollution. Which property of water is responsible for its pollution?

Q.24. Give four means by which presence of pollutants in water can be recognised.

Q.25. How is domestic sewage responsible for the death of aquatic animals?

Q.26. Fertilizers are good for crops but cause pollution of soil and water. Comment.’

Q.27. What steps can be taken by the government to stop water pollution?

3 marks Questions :-

Q28. Differentiate between Rabi crop and Kharif crops. Give two examples of each.

Q29. What are the various agricultural practices required for growing crops?

Q30. Differentiate between broadcasting and seed drill.

Q31. What is soil made up of ? What is the role of microorganisms in it ?

Q32. What is combustion? What happens when magnesium ribbon is burnt in presence of air?

Q33 How can we put off fire caused by ---(a) Oil or Gas (b) Kerosene (c) Electric short circuit

Q34 Define Flame. Why is non-luminous zone hottest part of flame?

Q35 Write an activity to show that wax vapours are present in the innermost zone of candle flame.

Q36. (a) How is the calorific value related to efficiency of a fuel?

(b) Which unit is used to express Calorific value?

Q37. Write an Activity to show that luminous zone of candle flame contains unburnt particles of carbon.

Q38. What causes global warming? What are its harmful effects?

Q.39. Write an activity to show that non-luminous zone is the hottest part of the flame.

Q.40. Why is LPG considered a better fuel than coal or kerosene ?

Lesson 10 REFRACTION AND DISPERSION OF LIGHT
Q.1. Define refraction of light.

Q.2. What is the cause of refraction of light?

Q.3. Define dispersion of light. Name the colour that is least  deviated.

Q.4. How does the bending  of the ray light depend upon refractive index of the medium?

Q.5.Give any two examples of refraction of light, which we observe in everyday life.

Q.6.You are given a convex and concave lens. How will you identify them without touching their surface?

Q.7. A coin, kept in a cup of water appears ‘raised up’. Why? 

Q.8. What is meant by optical density? Why does light bend when it travels through two optically different mediums?

Q.9. When and how is rainbow formed?

Q.10. A magnifying glass produces a hole on the black paper when sunlight is focused on it. Why?

Q.11. If the refractive index of the medium is high, will the bending of the light be more or less?

Q.12. Distinguish between a convex and a concave lens.

Q.13. Why does light split into several colours as it passes through  the prism?

Q.14. Define:- (a) Focal length (b) principal axis (c) radii of curvature with the help of a diagram.

Q.15. What will happen if you hold a torch vertically above the water surface, so that the ray of light is perpendicular to the water surface? What will happen to the speed of light as it travels from air to water?

Q.16. The speed of light in water is 225,000km/s. Calculate the refractive index of water. Given that speed of light in air is 300,000km/s.

Q.17.An object is placed at the following distances from a convex lens of focal length 10 cm-----
(a) 8cm (b) 15cm   Draw ray diagrams to show the nature , size and position of the image formed.

Q.18. What is a lens? State some of the application of lenses.

Q.19. Why does a pond appears less deep than it actually is? Explain with the help of a diagram.

Q.20. Define refractive index of a medium. 

LESSON-3 (HUMAN EYE) 

Q.1. Explain the working of Human Eye?

Q.2. How are we able to see in dim and bright light?

Q.3. What is the function of the ciliary Muscles?

Q.4. What kind of image is formed by Eye-lens?

Q.5. How we can see colours?

Q.6. What are Photoreceptors?

Q.7. What is persistence of vision?

Q.8. How does persistence of vision help to see the object as moving?

Q.9. What kind of problem develops when eye-lens becomes thick?

Q.10. What happens when an object is brought closer to the eye? Give a suitable reason for this.

Q.11. What are the different reasons for vision problems?

LESSON- 12 (SOUND)

Q.1. How are Amplitude and Loudness of sound related?

Q.2. The sound from a Mosquito is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the Time period of the vibration?

Q.3. How can a hearing impaired child communicate?

Q.4. Write some measures to limit Noise Pollution.

Q.5. Why is the voice of men, women and children different?

Q.6. Define Noise Pollution.

Q.7. Differentiate between Music and Noise.

Q.8. What is the audible range of sound for human beings?

Q.9. Differentiate between Infrasonic Sounds and Ultrasonic Sounds.

Q.10. People living near railway tracks know well in advance about an approaching train. Why?

LESSON-13 (SYNTHETIC FIBRES AND PLASTICS) 

Q.1. Give some examples of Natural and Synthetic fibers.

Q.2. What are Monomers and Polymers?

Q.3. What is Polymerization?

Q.4. What is Rayon?

Q.5. Give some features and uses of Terylene and acrylic fibers.

Q.6. What are the advantages of Synthetic fibers?

Q.7. Write some disadvantages of Synthetic fibers.

Q.8. What are Plastics? What are its different types?

Q.9. Differentiate between Thermoplastics and Thermosetting Plastics.

Q.10. What are the characteristics of Synthetic Plastics?

Q.11. Differentiate between Biodegradable and Non-Biodegradable materials.

Q.12. Give some measures to control the damage caused by plastic waste.

Q.13. Name the first fully synthetic fiber. What are its different uses?

Q.14. Should the handles and bristles of a toothbrush be made of the same material?

Q.15. Explain why the following are made of Thermosetting plastics – 
(i) Saucepan handles  (ii) Kitchenware

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