Class 8 Science - Chapter Synthetic Fibres and Plastics NCERT Solutions | Rana wants to buy shirts for summer. Sho

Describe an activity to show that thermoplastic is a poor conductor of electricity.

Explain why plastic containers are favoured for storing food.

‘Manufacturing synthetic fibres is actually helping conservation of forests’. Comment.

Give examples which indicate that nylon fibres are very strong.

Give examples to show that plastics are noncorrosive in nature.

Explain the difference between the thermoplastic and thermosetting plastics.

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 __________ .

Match the terms of column I correctly with the phrases given in column II.
       Column I                 Column II
  (i) Polyester           (a) Prepared by using wood pulp
  (ii) Teflon                (b) Used for making parachutes and stockings
  (iii) Rayon              (c) Used to make non-stick cookwares
  (iv) Nylon               (d) Fabrics do not wrinkle easily

‘Avoid plastics as far as possible’. Comment on this advice.

Should the handle and bristles of a tooth brush be made of the same material? Explain your answer.

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)

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.

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 ?

What is a constellation? Name any two constellations.

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

The bulb does not glow in the setup shown in Fig.14.10. List the possible reasons. Explain your answer.

Alida runs her toy car on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be :

(a) Wet marble floor, dry marble floor, newspaper and towel.
(b) Newspaper, towel, dry marble floor, wet marble floor.
(c) Towel, newspaper, dry marble floor, wet marble floor.
(d) Wet marble floor, dry marble floor, towel, newspaper

List changes in the body that take place at puberty.

In which female reproductive organ does the embryo get embedded?

Explain in what way noise pollution is harmful to humans.

Discuss the effects of deforestation on the following:
(a) Wild animals
(b) Environment
(c) Villages (Rural areas)
(d) Cities (Urban areas)
(e) Earth
(f) The next generation

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.

Choose the most appropriate answer:
(a) Internal fertilization occurs
      (i) in the female body.
      (ii) outside the female body.
      (iii) in male body.
      (iv) outside male body.

(b) A tadpole develops into an adult frog by the process of
      (i) fertilization   (ii) metamorphosis   (iii) embedding    (iv) budding

(c) The number of nuclei present in a zygote is
      (i) none   (ii) one    (iii) two    (iv) four