most difficult question of science
Answers
Answer:
1. Give an example of a unicellular and a multi-cellular organism.
2. How was cell discovered?
3. Define plant cell and animal cell?
4. How does a nerve cell function?
5. What are vacuoles?
6. Draw a neat diagram of an amoeba.
7. Explain the structure of a cell.
8. Where are chromosomes found in a cell?
9. What are plastids?
10. What is the function of chloroplasts?
1. Why it is dangerous to touch electrical appliances with wet hands?
2. Name substances which make any liquid good conductor of electricity?
3. Name the part of bulb that glows.
4. Does distilled water conduct electricity?
5. Name the gas deposited on negative electrode.
6. How can you test liquids conduct or do not conduct the electricity?
7. Explain why a bulb glows on passing current.
8. What is chemical effect of electricity? Give some examples of chemical effects.
9. What are the two methods of testing an insulator or conductor?
10. Write true/False
a. Rubber is an insulator.
b. Electroplating causes rusting.
c. Vinegar can __________ electricity.
1. Name two man-made substances, two natural and two exhaustible substances.
2. Name the gas which is formed when coal is heated in the absence of air.
3. Where was the first oil well drilled?
4. How many substances are found in coal tar?
5. Name the places where natural gas is found in India.
6. What are exhaustible natural resources? Explain with exampes.
7. What is coal gas? Write its uses.
8. What is petroleum? What is it called black gold?
9. Describe the process of formation of coal in the nature.
10. What is main component of LPG?
1. What is the difference between burning of a candle and burning of coal?
2. Classify fuels?
3. Write name of some incombustible substances
4. What do you mean by an ignition temperature?
5. What are the requirements to produce fire?
6. How many types of combustion are there?
7. Give examples of the substances which give flame.
8. What substances are used to extinguish fire in case of electric short circuit?
9. Which zone of flame has highest temperature?
10. Explain structure of flame.
11. What are the characteristics of good fuel?
12. What are the ill effects due to the increasing consumption of fuel?
13. Draw a diagram to explain that air is essential for combustion.
14. What are the products of any fuel?
1. Identify the agent exerting force and the object on which it acts when a piece of lemon is squeezed between fingers and juice come out.
2. Explain that force are due to an interaction between objects.
3. What are the effects of force?
4. Explain contact and non-contact forces?
5. Explain the force of gravity?
6. If the area of head is 15cmX15cm, how much air (in weight) would you carry on your head?
7. Does the application of force result in change of state of motion of the object.
8. What do you meant by pressure? How can we increase the pressure by exerting same force?
9. Give two factors which affect the effect of changes?
10. How to describe state of motion?
1. Does friction depend on the nature of objects?
2. Which type of surface produces more friction?
3. Which type of surface produces less friction?
4. Which is less sliding friction or static friction?
5. Why is it difficult to move on a wet marble floor?
6. What would happen when an object starts moving if there is no friction?
7. Give two examples where friction is undesirable?
8. Our hands become warm when we rub them. Why?
9. Why do we shape aero planes like that of bird?
10. Write some methods to reduce friction?
11. Write various types of friction.
12. What is a fluid friction? Write the factors on which fluid friction depends.
1. Where does the image form is our eye?
2. What is the shape of human eye?
3. What is the working of iris?
4. Define normal?
5. Define angle of incidence?
6. What is a reflection of light? State laws of reflection.
7. How will you prove that the angle of incidence is equal to the angle of reflection.
8. Explain the structure and working of a human eye.
9. What is blindness? How many types of blindness do we know about?
1. What are viruses? Name some common diseases in human caused by virus.
2. Explain the formation of curd from the milk.
3. Mention some beneficial effects of bacteria.
4. Explain the discovery of Pencillin.
5. How do microorganisms spoil food?
6. What are carriers of disease causing microbes? Explain with the help of two examples.
7. Explain nitrogen cycle and draw a schematic diagram of nitrogen cycle.
8. Name some common plant diseases their causative microorganisms mode of transmission with the help of the figures.
9. Explain the uses of Bacteria, Fungi and Algae.
10. What are food preservatives? Explain some common food preservatives.
1. Which gas is responsible for greenhouse effect?
2. What is global warming?
3. Which fuel is pollution free?
4. What are alternative renewable fuels?
5. What do you mean by �Van Mahotsav�?
6. What is water pollution and its causes?
7. What is smog?
8. What are effects of global warming/
9. What is portable water? Write its properties.
10. Explain process of water treatment to make it drinkable.