materials-metals-and-non-metalsWHERE cd.courseId=12 AND cd.subId=16 AND chapterSlug='materials-metals-and-non-metals' and status=1SELECT ex_no,page_number,question,question_no,id,chapter,solution FROM question_mgmt as q WHERE courseId='12' AND subId='16' AND chapterId='367' AND ex_no!=0 AND status=1 ORDER BY ex_no,CAST(question_no AS UNSIGNED) CBSE Class 8 Free NCERT Book Solution for Science

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Chapter 4 : Materials: Metals and Non-Metals


  • Metals are good conductor of electricity and heat whereas non- metals are poor conductor of electricity and heat.
  • Metals are lustrous whereas non- metals are not lustrous.
  • Malleability is the property of metals by which metals can be drawn into thin sheets. Non- metals does not shows malleability.
  • Ductility is the property of metals by which they can be drawn into wires. Non- metals does not show the ductility. Hence, they are not ductile.
  • In the presence of air, metal forms metal oxide to react with the oxygen.
  • Metal oxides are basic in nature whereas non- metallic oxides are acidic in nature.
  • On reacting with water, metal produce metal hydroxides and hydrogen gas.
  • Non- metals does not react with water.
  • On reaching with acids, metals produce metal salt and hydrogen gas whereas non- metals do not reacts with acids.
  • Metal produces hydrogen gas on reacting with the base.
  • Atoms are the smallest unit which cannot be divided into the smaller one.
  • The materials or substances through which heat and electricity can pass easily are called as conductor. Metals are good conductor of electricity whereas non- metals are poor conductor.
  • The reaction in which a higher reactive element displace the less reactive element from its place, then the reaction is called as displacement reaction.
  • Substances which cannot be broken down into simpler substances are called as elements.
  • Hardness is defined as the rigidity of the substance, by which the substance cannot be broken down easily.
  • The elements which shows the properties of both metal and non- metals are known as metalloids.
  • The property of metal due to which it produces ringing sound. It is called as sonorous.

Exercise 1 ( Page No. : 55 )
Q:
A:

(a) Zinc

The properties of metal by which they can be beaten into thin sheets is called malleability. For example: zinc.


Exercise 1 ( Page No. : 55 )
Q:
A:

(c) Generally, metals are ductile

Generally metals are ductile but some exceptions are there like mercury is a metal which is liquid at room temperature. It cannot be drawn into wires, so it is not ductile.  


Exercise 1 ( Page No. : 55 )
Q:
A:

(a) Reactive

Phosphorus is an reactive non- metal. It catches fire easily when exposed to air.

(b) Good, electricity

Conductors are those from which heat and electricity can pass through easily. Metals are good conductor of heat and electricity.

(c) More

Iron is more reactive than copper so it can replace copper easily from its solution.

(d) Hydrogen

When metal reacts with acid. It produces hydrogen gas which burns with a pop sound whereas non- metal generally do not react with acids.


Exercise 1 ( Page No. : 55 )
Q:
A:

(a) False

This statement is false because non- metals generally do not react with metal whereas metal does.

(b) True

This statement is true because, sodium is a very reactive metal. It is stored in kerosene, it catches fire easily.

(c) False

This statement is false because copper is less reactive than zinc. So, it cannot displace it.

(d) False

This statement is false because coal cannot be drawn into wires. Coal is a form of carbon which is a non- metal. Non- metal does not show the property of ductility.


Exercise 1 ( Page No. : 55 )
Q:
A:
  1. Metals are bright or lustrous in appearance whereas non- metals are dull.
  2. Generally metals are hard and non- metals are soft.
  3. Property of metal by which they can be beaten into thin sheets which is known as malleability whereas non- metals does not show this property.
  4. Property of metals by which they can be drawn into wires are called as ductility whereas non- metal does not show this property.
  5. Conductors are those from which heat and electricity can pass through easily. Metals are good conductor of heat whereas non- metals are poor conductor of heat.
  6. Metals are good conductor of electricity whereas non- metals are poor or bad conductor of electricity.

Exercise 1 ( Page No. : 55 )
Q:
A:
  1. Aluminium is highly malleable and it can easily beaten in the sheets to make its foil for the wrapping purposes. It is also soft and does not reacts with food items; and this is the reason that aluminium foils are used to wrap food items.
  2. Immersion rods made up of metallic substances because metals are good conductor of heat and electricity. They get hot very soon on the passage of electric current and warm the water soon.
  3. Copper is less reactive than zinc. So, it cannot displace zinc from its solution.
  4. Sodium and potassium are highly reactive, so they are stored in kerosene.

Exercise 1 ( Page No. : 55 )
Q:
A:

No, we cannot store lemon pickle in an aluminium utensil because aluminium is a metal and metals readily react with acid to produce hydrogen. When aluminium comes in contact with lemon, which is acidic, would react to give hydrogen and the pickle will be spoiled. 


Exercise 1 ( Page No. : 55 )
Q:
A:
Column I Column II
 (i)  Gold
 (ii) Iron
 (iii) Aluminium
 (iv) Carbon
 (v) Copper
 (vi) Mercury		  (d) Jewellery
 (e) Machinary
 (c) Wrapping food
 (d) Fuel
 (b) Electric Wire
 (a) Thermometers
  1. Gold is used in making jewelry and making ornaments.
  2. Iron is a hard metal, it is used in machinery.
  3. Aluminium is used in wrapping food items, it protect the food items from the bacteria and the humidity.
  4. Carbon is used as a fuel, in the form of coal and petroleum.
  5. Copper is a metal which is used in making electric wire because copper is a good conductor of heat and electricity.
  6. Mercury is a metal which is liquid at room temperature. It is used in thermometers usually.

Exercise 1 ( Page No. : 55 )
Q:
A:
  1. No reaction will take place because copper is very less reactive.
  2. Iron is more reactive than copper and then it will replace copper from its solution and brown coating of copper is deposited on the iron nails. Also, the blue colour turns into the green colour.

          Iron + Copper Sulphate (Solution) → Iron sulphate (FeSO4) solution + Copper


Exercise 1 ( Page No. : 55 )
Q:
A:
  1. Saloni find the nature of the gas by using a wet litmus paper. After bringing the litmus paper in contact with the gas; if it turns the blue litmus paper into red then it is acidic. Similarly, if it turns the red litmus into blue then it is basic.
  2. (i) Carbon (C) + Oxygen (O2) → Carbon dioxide (CO2)

(ii) CO2 + Lime water → Milky


Exercise 1 ( Page No. : 55 )
Q:
A:

Jeweller dipped the jewelry in a liquid solution called aqua regia to polish a gold ornament. Aqua regia is a mixture of hydrochloric acid and nitric acid. The outer layer of gold is dissolved in aqua regia and the inner shiny layer appears. Reduction of weight of gold is occurs due to the dissolution of outer layer of gold in aqua regia solution.   


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