List of top Science Questions asked in CBSE Class VIII

Find out the position of the image of an object situated at A in the plane mirror

(a) Find out the position of the image of an object situated at A in the plane mirror.
(b) Can Paheli at B see this image?
(c) Can Boojho at C see this image?
(d) When Paheli moves from B to C, where does the image of A move?
Identify the part which vibrates to produce sound in the following instruments.
  1. Dholak
  2. Sitar
  3. Flute
The process that you saw in Activity 11.7 is used for purification of copper. A thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from impure rod is sought to be transfered to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?
electroplating
In the following statements, tick ‘T’ against those which are true, and ‘F’ against those which are false.
  1. Sound cannot travel in vacuum. (T/F)
  2. The number of oscillations per second of a vibrating object is called its time period. (T/F)
  3. If the amplitude of vibration is large, sound is feeble. (T/F)
  4. For human ears, the audible range is 20 Hz to 20,000 Hz. (T/F)
  5. The lower the frequency of vibration, the higher is the pitch. (T/F)
  6. Unwanted or unpleasant sound is termed as music. (T/F)
  7. Noise pollution may cause partial hearing impairment. (T/F)
Explain why sliding friction is less than static friction.
Explain why a charged body loses its charge if we touch it with our hand.
Boojho stands at A just on the side of a plane mirror as shown in Fig. 
Boojho stands at A just on the side of a plane mirror
Can he see himself in the mirror? Also, can he see the image of objects situated at P, Q and R?
Define asexual reproduction. Describe two methods of asexual reproduction in animals.
In the following situations identify the agent exerting the force and the object on which it acts. State the effect of the force in each case.
1. Squeezing a piece of lemon between the fingers to extract its juice.
2. Taking out paste from a toothpaste tube.
3. A load is suspended from a spring while its other end is on a hook fixed to a wall.
4. An athlete making a high jump to clear the bar at a certain height.
Sketch larynx and explain its function in your own words.
Match the organisms in Column A with their action in Column B.

A

B

(i)Bacteria(a)Fixing nitrogen
(ii)Rhizobium(b)Setting of curd
(iii)Lactobacillus(c)Baking of bread
(iv)Yeast(d)Causing malaria
(v)A protozoan(e)Causing cholera
(vi)A virus(f)Causing AIDS
 (g)Producing antibodies
Describe with the help of a diagram an instrument which can be used to detect a charged body.
Fill in the blanks:
  1. Fossil fuels are ___, ___ and ___.
  2. Process of separation of different constituents from petroleum is called ___.
  3. Least polluting fuel for vehicle is ___.
What are the advantages of using CNG and LPG as fuels?

Select the correct word from the following list and fill in the blanks.
float, water, crop, nutrients, preparation

  1. The same kind of plants grown and cultivated on a large scale at a place is called ____.
  2. The first step before growing crops is ____ of the soil.
  3. Damaged seeds would ____ on top of water.
  4. For growing a crop, sufficient sunlight and ____ and ____ from the soil are essential.
Explain how deforestation leads to reduced rainfall.
Fill in the blanks:
  1. Most liquids that conduct electricity are solutions of ___, ___ and __.0.
  2. The passage of an electric current through a solution causes ___ effects.
  3. If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the ___ terminal of the battery.
  4. The process of depositing a layer of any desired metal on another material by means of electricity is called ___.
In order to meet the ever-increasing demand in factories and for shelter, trees are being continually cut. Is it justified to cut trees for such projects? Discuss and prepare a brief report.
In an experiment \(4.5\) kg of a fuel was completely burnt. The heat produced was measured to be \(180,000\) kJ. Calculate the calorific value of the fuel.
Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?
If wheat is sown in the kharif season, what would happen? Discuss.
Give reasons.
  1. Water is not used to control fires involving electrical equipment.
  2. LPG is a better domestic fuel than wood.
  3. Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not. 
Fill in the blanks:
  1. Burning of wood and coal causes ___ of air.
  2. A liquid fuel, used in homes is ___.
  3. Fuel must be heated to its ___   ___ before it starts burning.
  4. Fire produced by oil cannot be controlled by ___.
The bulb does not glow in the setup shown in Fig.11.10. List the possible reasons. Explain your answer.
bulb setup
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?