Friday, March 8, 2013

CBSE 8th Science[Practice Paper]-1

LESSON -1 (The Cell – Its structure and Functions) [Source:DAV Ballabhgarh]
LESSON -2 (Microorganisms : Friends or Foes )

NOTE— to 30 carry two marks to 35 carry three marks each.

Q.1 Differentiate between chloroplasts and chromoplasts.

Q.2 Why were the cells remained undiscovered for a long time?

Q.3 Name the unit used to express cell size. Express its value in metres.

Q.4 What is the function of albumen and yolk in an egg?

Q.5 What is the composition and function of cytoplasm?

Q.6 Describe the structure of nucleus.

Q.7 What is the importance of cilia and flagella ?

Q.8 Describe the various levels of organization.

Q.9 Why do plant cells have cell wall?

Q.10 Classify the living organisms on the basis of the cell number.

Q.11 What advantage does amoeba derive by changing shape?

Q.12 A hen’s egg can be seen easily. Is it a cell or a group of cells? Give reason.

Q.13 Are the cells in an elephant larger than the cells in a rat? Justify your answer.

Q.14 Why do vaccum packed chips not get spoiled?

Q.15 How does boiling of milk prevent its spoilage?

Q.16 A child is suffering from cholera. Answer the following------

(a) Name the causative agent and mode of transmission for the disease.

(b) State any two preventive measures against the disease.

Q.17 What are toxins? How do they affect our body?

Q.18 Why is yeast used in baking industry?

Q.19 Why are certain microbes commonly called biological nitrogen fixers ?

Q.20 What are the different modes of transmission of communicable diseases?

Q.21 How are microorganisms useful in fuel production?

Q.22 “Milk tastes sweet while curd tastes sour”. Give a suitable reason to justify this statement.

Q.23 What was the reason for Irish Famine in 1740-41 ?

Q.24 What is food poisoning? What are its symptoms? Name a bacteria and virus that cause this disease.

Q.25 How does the drying method help to preserve the food items?

Q.26 Why is salt used in the preservation of meat and fish?

Q.27 How is canning of food done?

Q.28 Name two acids added in carbonated beverages. Why are these acids used?

Q.29 Write two importance of food preservation.

Q.30 How do bacteria cause damage to teeth?

Q.31 Name two factors that affect the shape of the cell. Explain by giving an example.

Q.32 Define the following terms --- (i) organelles (ii) cell membrane (iii) cytoplasm

Q.33 A child suffering from chicken pox was taken to a doctor. The doctor told the parents that they should have got their child vaccinated earlier. Answer the following-

(i) How vaccination would have helped the child to develop immunity against the disease?

(ii) Name two viral diseases for which vaccinations are available for children other than chicken pox.

(iii) Name two methods used for administering vaccines .

Q.34 Define Rancidity , Food Preservation and Bioaugmentation.

Q.35 What is pasteurization? Why is it done? Why is pasteurized milk stored under refrigerator?


NOTE— to 16 carry two marks to 25 carry three marks each.

Q.1. Differentiate between minerals and ores.

Q.2. What are metalloids? Give some examples.

Q.3. What do you mean by Reactivity and Reactivity Series.

Q.4. What is a displacement reaction? Give an example.

Q.5. What happens when Mg ribbon is put into CuSO4 soluition? Write the balanced chemical equation also.

Q.6. Why is pure gold not suitable for making jewellery?

Q.7. Why is iron metal known as the backbone of the industry ?

Q.8. Why is Ag metal not used for making electrical wires?

Q.9. Why is aluminium foil used to wrap food items?

Q.10. Why are immersion rods for heating liquids are made up of metallic substances?

Q.11. Write some common uses of Cu metal.

Q.12. What will happen when we put Cu rod in ZnSO4 solution? Give suitable reason.

Q.13. Can you store lemon pickle in an aluminium utensil? Explain.

Q.14. Suhaani took a piece of burning charcoal and collected the gas evolved in the test tube.

(a) How will she find the nature of the gas?

(b) Write down the word equations of all the reactions taking place in this process.

Q.15. How is Carboxy Haemoglobin harmful to humans?

Q.16. What are the harmful effects of CFCs?

Q.17. Define the following terms—malleability , ductility ,sonorosity.

Q.18. How will you show that magnesium oxide is basic in nature?

Q.19. Write two uses each of the following metals--- Au ,Ag ,Pt.

Q.20. Write some common uses of non-metals.

Q.21. What are the harmful effects of nitrogen dioxide? How is it produced in the atmosphere?

Q.22. What is Global Warming? What are its harmful effects?

Q.23. How is Carbon Monoxide produced? How does it affect the growth of plants?

Q.22. Why is greenhouse effect named so?

Q.23. What are the consequences of acid rain?

Q.24. How does CO2 content rise in the atmosphere and become excessive?

Q.25. What is marble cancer? Explain it by giving a suitable example.

Q.No. 1 to 15 and 20 to 25 carry 2 marks each and Q.No. 16 to 19 and 26 to 30 carry 3 marks each.

Q.1. What happens when two unbalanced forces act on an object in the—

(a) same direction (b) opposite direction

Q.2. The walls of a plastic bottle are seen to get deformed if hot water is poured in it. Explain.
Q.3. State any two uses of atmospheric pressure in our day to day life.

Q.4. How does a force, acting along the direction of motion of an object, affect its motion?

Q.5. What happens when we press rubber sucker on a plain smooth surface?

Q.6 . State the properties of liquid pressure.

Q.7. For a given applied force, which of the two—a car or a truck- gains in speed at a faster rate? Why? 

Q.8. What is atmospheric pressure ? Why do we not feel atmospheric pressure acting on us?

Q.9. Why does a fountain pen start leaking at higher altitude?

Q.10. What are the different effects of force?

Q.11. What are the parameters that determine the magnitude of force needed ?

Q.12. Differentiate between balanced and unbalanced forces.

Q.13. Why do aircrafts have ‘pressurized cabins’?

Q.14. Why are shoulder bags provided with broad straps and not thin strap?

Q.15. An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth .It was found that the balloon sticks to the wall .What force might be responsible for the attraction between the balloon and the wall? Give reason.

Q.16. Do gases exert pressure on the walls of the container? Explain by giving a suitable example .

Q.17. Write an activity to show that pressure exerted by water at the bottom of the container depends on the height of its column .

Q.18. Define pressure . Why is it easier to push the nail by the pointed end?

Q.19. An archer stretches her bow while taking aim at the target. She then releases the arrow, which begins to move towards the target. 
Based on this information fill up the gaps in the following statements using the appropriate words.
(a) To stretch the bow, the archer applies a force that causes a change in its___________.
(b) The force applied by the archer to stretch the bow is an example of __________ force.
(c) The type of force responsible for a change in the state of motion of the arrow is an example of a ______________________ force.
(d) While the arrow moves towards its target, the force acting on it are due to __________ and that is due to ______________ of air.
Lesson---5 (FRICTION) 
Q.20 What do you understand by the term ‘limiting force of friction’?

Q.21. Why do we find it easier to maintain an object in motion than to start it from rest?

Q.22. You spill a bucket of soapy water on a marble floor accidently.Would it make it easier or difficult for you to walk on the floor? Why?

Q.23. Rahul has to push a heavier box and Reeta has to push a similar lighter box on the same floor. Who will have to apply a larger force and why?

Q.24. What is fluid friction? On which factors does it depend?

Q.25 How does compressed air act as a lubricant?

Q.26. Give reasons for the following---
(a) Sole of our shoes wear out.
(b) Gymnasts apply chalk powder on their hands before their performance.
(c) The shape of a boat is some what similar to that of a fish.
Q.27. Explain briefly the cause of friction. On which factors does the force of friction depend?

Q.28. What is rolling friction? How is this rolling friction useful to laborers?

Q.29. Write an activity to show that fluid friction depends on the shape of the objects moving through the fluid.

Q.30. “Friction can produce heat which can be useful as well as harmful”. Give suitable examples to prove this statement.

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