Class 8 Science - Chapter Materials: Metals and Non-Metals NCERT Solutions | Give reasons for the following: (a) Alu

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

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

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.

In the following Table some substances are given in Column I. In Column II some uses are given. Match the items in column I with those in Column II.

Mark ‘T’ if the statement is true and ‘F’ if it is false.

(a) Generally non-metals react with acids.                          (  )
(b) Sodium is a very reactive metal.                                    (  )
(c) Copper displaces zinc from zinc sulphate solution.       (  )
(d) Coal can be drawn into wires.                                        (  )

Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
(a) How will she find the nature of the gas ?
(b) Write down word equations of all the reactions taking place in this process.

What happens when
(a) Dilute sulphuric acid is poured on a copper plate?
(b) Iron nails are placed in copper sulphate solution?
      Write word equations of the reactions involved.

One day Reeta went to a jeweller’s shop with her mother. Her mother gave old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?

Which of the following statements is correct?
(a) All metals are ductile.
(b) All non-metals are ductile.
(c) Generally, metals are ductile.
(d) Some non-metals are ductile.

Some properties are listed in the following Table. Distinguish between metals and non-metals on the basis of these properties.

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 ?

Explain the importance of reproduction in organisms.

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

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?

What is a constellation? Name any two constellations.

A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?

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

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

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.

Describe the construction of a kaleidoscope.

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

Make sketches of animal and plant cells. State three differences between them.