Class 8 Science - Chapter Some Natural Phenomena NCERT Solutions | Sometime, a crackling sound is heard whi

Describe with the help of a diagram an instrument which can be used to detect a charged body.

Explain why a charged body loses its charge if we touch it with our hand.

Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?

Suggest three measures to protect ourselves from lightning.

Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?

Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage?

List three states in India where earthquakes are more likely to strike.

When a glass rod is rubbed with a piece of silk cloth the rod
(a) and the cloth both acquire positive charge.
(b) becomes positively charged while the cloth has a negative charge.
(c) and the cloth both acquire negative charge.
(d) becomes negatively charged while the cloth has a positive charge.

The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella? Explain.

Which of the following cannot be charged easily by friction?
(a) A plastic scale
(b) A copper rod
(c) An inflated balloon
(d) A woollen cloth.

Which of the following can be beaten into thin sheets?
  (a) Zinc     (b) Phosphorus     (c) Sulphur     (d) Oxygen

Fill in the blanks
(a) Most liquids that conduct electricity are solutions of , ______________ and ______________.
(b) The passage of an electric current through a solution causes ______________ effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the terminal of the battery.
(d) The process of depositing a layer ofany desired metal on another material by means of electricity is called .

Give two examples each of situations in which you push or pull to change the state of motion of objects.

Fill in the blanks:
(a) Friction opposes the _____________ between the surfaces in contact with each other.
(b) Friction depends on the _____________ of surfaces.                                                                                                                                                                      (c) Friction produces __________.
(d) Sprinkling of powder on the carrom board ________ friction.
(e) Sliding friction is ___________ than the static friction.

List conditions under which combustion can take place.

Indicate whether the following statements are True (T) or False (F).
(a) Unicellular organisms have one-celled body. (T/F)
(b) Muscle cells are branched. (T/F)
(c) The basic living unit of an organism is an organ. (T/F)
(d) Amoeba has irregular shape. (T/F)

Fill in the blanks:
(a) A place where animals are protected in their natural habitat is called                  .
(b) Species found only in a particular area is known as                          .
(c) Migratory birds fly to far away places because of                     changes.

Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room. Explain.

What are the different ways in which water gets contaminated ?

Explain the importance of reproduction in organisms.

Fill in the blanks in the following statements:
(a) To draw water from a well we have to ——— at the rope.
(b) A charged body ———— an uncharged body towards it.
(c) To move a loaded trolley we have to ———— it.
(d) The north pole of a magnet ———— the north pole of another magnet.

Fill in the blanks with appropriate words:

(a) Synthetic fibres are also called ______ or _______ fibres.
(b) Synthetic fibres are synthesised from raw material called ________.
(c) Like synthetic fibres, plastic is also a __________ .

Fill in the blanks with suitable words.
(a) Time taken by an object to complete one oscillation is called ................... .
(b) Loudness is determined by the .........................of vibration.
(c) The unit of frequency is..........................
(d) Unwanted sound is called ......................... .
(e) Shrillness of a sound is determined by the ................. of vibration.

Explain why objects moving in fluids must have special shapes.

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

Describe the construction of a kaleidoscope.

Explain the importance of reproduction in organisms.

Define asexual reproduction. Describe two methods of asexual reproduction in animals.

Tick the correct answer:

(a) Yeast is used in the production of
      (i) sugar     (ii) alcohol     (iii) hydrochloric acid     (iv) oxygen

(b) The following is an antibiotic
      (i) Sodium bicarbonate     (ii) Streptomycin      (iii) Alcohol     (iv) Yeast

(c) Carrier of malaria-causing protozoan is
      (i) female Anopheles mosquito     (ii) cockroach     (iii) housefly     (iv) butterfly

(d) The most common carrier of communicable diseases is
      (i) ant     (ii) housefly     (iii) dragonfly     (iv) spider

(e) The bread or idli dough rises because of
      (i) heat     (ii) grinding     (iii) growth of yeast cells     (iv) kneading

(f) The process of conversion of sugar into alcohol is called
     (i) nitrogen fixation     (ii) moulding     (iii) fermentation     (iv) infection

It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Explain.