NCERT Solutions For Class 8 Science Chapter 4 Exercise
Chapter 4 – Materials: Metals and Non-Metals
Questions:
1)Which of the following can be beaten into thin sheets?
(a) Zinc
(b) Phosphorus
(c) Sulphur
(d) Oxygen
The answer is a) Zinc
In this case, zinc is a metal that is malleable and ductile, but phosphorus, sulphur, and oxygen are nonmetals that are not.
2)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.
The answer is (c) Generally, metals are ductile.
The ability of a material to condense into thin wires is known as ductility. Mercury is the exception to the rule that metals are ductile.
3)Fill in the blanks.
(a) Phosphorus is a 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) Phosphorus is a very reactive non-metal.
(b) Metals are good conductors of heat and electricity.
(c) Iron is more reactive than copper.
(d) Metals react with acids to produce hydrogen gas.
4)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. ( )
a) False
b) True
c) False
d) False
5)Give reasons for the following.
(a) Aluminium foils are used to wrap food items.
(b) Immersion rods for heating liquids are made up of metallic substances.
(c) Copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are stored in kerosene
a) Food items are wrapped in aluminium foil because aluminium is pliable and can be formed into thin sheets.
b) Metal is used to make immersion rods for heating liquids since it is a good heat and electrical conductor.
c) Zinc is more reactive than copper, hence zinc cannot be removed from its salt solution by copper.
d) Because sodium and potassium are extremely reactive metals that easily catch fire when they come into contact with oxygen in the atmosphere, they are kept in kerosene.
6) Can you store lemon pickles in an aluminium utensil? Explain.
Pickles contain acids that react with aluminium to create hydrogen and salt. As a result, pickles are not kept in aluminium cookware.
7) Match the substances given in Column A with their uses given in Column B.
A
B
(i) Gold
(a) Thermometers
(ii) Iron
(b) Electric wire
(iii) Aluminium
(c) Wrapping food
(iv) Carbon
(d) Jewellery
(v) Copper
(e) Machinery
(vi) Mercury
(f) Fuel
Solution –
A
B
(i) Gold
(d) Jewellery
(ii) Iron
(e) Machinery
(iii) Aluminium
(c) Wrapping food
(iv) Carbon
(f) Fuel
(v) Copper
(b) Electric wire
(vi) Mercury
(a) Thermometers
8) What happens when
(a) Dilute sulphuric acid is poured on a copper plate.
(b) Iron nails are placed in a copper sulphate solution?
Write word equations of the reactions involved.
9) 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.
Solution:
a) Put a few drops of water into a test tube that is filled with gas. Shut off the test tube and give it a good shake. Use blue litmus to test the fluid after shaking. It will turn red instead of blue. As a result, gas is naturally acidic.
b) Carbon dioxide gas is created when charcoal and oxygen combine.
10) One day Reeta went to a jeweller’s shop with her mother. Her mother gave old gold jewellery to the goldsmith to polish. The 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?
The gold ornament needs to be immersed into a solution known as aqua regia, which is a solution made of hydrochloric and nitric acids, to polish it. The exterior coating of gold melts when submerged in aqua regia, revealing an inner, glossy layer. The jewellery loses weight as a result of the coating melting.
