Class 8 Science - Chapter Stars and The Solar System NCERT Solutions | Explain how you can locate the Pole Star

What is a constellation? Name any two constellations.

Draw sketches to show the relative positions of prominent stars in
(a) Ursa Major and (b) Orion

Boojho made the following sketch (Fig. 17.29) of the solar system. Is the sketch correct? If not, correct it.

Name two objects other than planets which are members of the solar system.

Why is the distance between stars expressed in light years? What do you understand by the statement that a star is eight light years away from the Earth?

Do all the stars in the sky move? Explain.

Phases of the moon occur because

(a) we can see only that part of the moon which reflects light towards us.
(b) our distance from the moon keeps changing.
(c) the shadow of the Earth covers only a part of moon’s surface.
(d) the thickness of the moon’s atmosphere is not constant.

The radius of Jupiter is 11 times the radius of the Earth. Calculate the ratio of the volumes of Jupiter and the Earth. How many Earths can Jupiter accomodate?

Name the largest planet of the solar system.

Which of the following is NOT a member of the solar system?
(a) An asteroid
(b) A satellite
(c) A constellation
(d) A comet

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 ?

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.

Fill in the blanks :
(a) Phosphorus is very _________ non-metal.
(b) Metals are ________ conductors of heat and ________ .
(c) Iron is __________ reactive than copper.
(d) Metals react with acids to produce _________ gas.

(a) Find out the position of the image of an object situated at A in the plane mirror (Fig. 16.21).
(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:
(a) Dholak (b) Sitar (c) Flute

What are weeds? How can we control them?

Explain why fossil fuels are exhaustible natural resources.

Complete the following word puzzle with the help of clues given below. 

Down
1. Providing water to the crops.
2. Keeping crop grains for a long time under proper conditions.
5. Certain plants of the same kind grown on a large scale.

Across
3. A machine used for cutting the matured crop.
4. A rabi crop that is also one of the pulses.
6. A process of separating the grain from chaff.

Complete the crossword with the help of clues given below:
Across
1. This is necessary for photosynthesis.
3. Term for component present in the cytoplasm.
6. The living substance in the cell.
8. Units of inheritance present on the chromosomes.

Down
1. Green plastids.
2. Formed by collection of tissues.
4. It separates the contents of the cell from the surrounding medium.
5. Empty structure in the cytoplasm.
7. A group of cells.

Draw a labeled sketch of the human eye.

Boojho stands at A just on the side of a plane mirror as shown in Fig. 16.20. Can he see himself in the mirror? Also can he see the image of objects situated at P, Q and R?