Class 8 Science - Chapter Chemical Effects of Electric Current NCERT Solutions | The process that you saw in Activity 14.

In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Explain why they do this.

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

Does pure water conduct electricity? If not, what can we do to make it conducting?

Prepare a list of objects around you that are electroplated.

Name three liquids, which when tested in the manner shown in Fig.14.9, may cause the magnetic needle to deflect.

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 .

Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.

Paheli had heard that rainwater is as good as distilled water. So she collected some rainwater in a clean glass tumbler and tested it using a tester. To her surprise she found that the compass needle showed deflection. What could be the reasons?

A tester is used to check the conduction of electricity through two liquids, labeled A and B. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. You would conclude that

(i) liquid A is a better conductor than liquid B.
(ii) liquid B is a better conductor than liquid A.
(iii) both liquids are equally conducting.
(iv) conducting properties of liquid cannot be compared in this manner.

When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?

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

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 ?

Explain the importance of reproduction in organisms.

Describe characteristics and uses of coke.

Suggest three measures to protect ourselves from lightning.

Give examples which indicate that nylon fibres are very strong.

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.

Why should paper be saved? Prepare a list of ways by which you can save paper.

The table below shows the data on likely heights of boys and girls as they grow in age. Draw graphs showing height and age for both boys and girls on the same graph paper. What conclusions can be drawn from these graphs?

Which of the following is not a greenhouse gas?
(a) Carbon dioxide
(b) Sulphur dioxide                                                                                                                                                                                                                                  (c) Methane
(d Nitrogen

Name the petroleum product used for surfacing of roads.

Lightning and thunder take place in the sky at the same time and at the same distance from us. Lightning is seen earlier and thunder is heard later. Can you explain?

Prepare a Table having two columns depicting names of endocrine glands and hormones secreted by them.