Class 8 Science - Chapter Combustion and Flame NCERT Solutions | Make a labelled diagram of a candle flam

Give reasons:
(a) Water is not used to control fires involving electrical equipment.
(b) LPG is a better domestic fuel than wood.
(c) Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not.

Compare LPG and wood as fuels.

Explain how CO₂ is able to control fires.

Fill in the blanks:
(a) Burning of wood and coal causes                   of air.
(b) A liquid fuel, used in homes is                            .
(c) Fuel must be heated to its                                    before it starts burning.
(d) Fire produced by oil cannot be controlled by                        .

Explain how the use of CNG in automobiles has reduced pollution in our cities.

Abida and Ramesh were doing an experiment in which water was to be heated in a beaker. Abida kept the beaker near the wick in the yellow part of the candle flame. Ramesh kept the beaker in the outermost part of the flame. Whose water will get heated in a shorter time?

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

Which zone of a flame does a goldsmith use for melting gold and silver and why?

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.

Name the unit in which the calorific value of a fuel is expressed.

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.

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 ?

Explain the importance of reproduction in organisms.

What is a constellation? Name any two constellations.

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.

Indicate whether the following statements are True (T) or False (F):
(a) Oviparous animals give birth to young ones.                                    ( )
(b) Each sperm is a single cell.                                                              ( )
(c) External fertilization takes place in frog.                                           ( )
(d) A new human individual develops from a cell called gamete.          ( )
(e) Egg laid after fertilization is made up of a single cell.                       ( )
(f) Amoeba reproduces by budding.                                                       ( )
(g) Fertilization is necessary even in asexual reproduction.                  ( )
(h) Binary fission is a method of asexual reproduction.                         ( )
(i) A zygote is formed as a result of fertilization.                                    ( )
(j) An embryo is made up of a single cell.                                              ( )

Explain how you can locate the Pole Star with the help of Ursa Major.

What are the advantages of using CNG and LPG as fuels?

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)

Can microorganisms be seen with the naked eye? If not, how can they be seen?

A child staying in a coastal region tests the drinking water and also the seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?

Write a short paragraph on the harms caused by microorganisms.

Tick True/False against the following statements :

(a) Fossil fuels can be made in the laboratory. (T/F)
(b) CNG is more polluting fuel than petrol. (T/F)
(c) Coke is almost pure form of carbon. (T/F)
(d) Coal tar is a mixture of various substances. (T/F)
(e) Kerosene is not a fossil fuel. (T/F)