Some More Written Practice Questions

Q1. What are metals? What are its properties?

Ans. Metals are opaque, lustrous elements that are good conductors of heat and electricity. Most metals are malleable and ductile and are, in general, denser than the other elemetal substances.

Physical Properties

  • Shiny in nature
  • Good conductor of heat and elelctricity
  • Density is high
  • High melting point
  • Ductile

 Chemical Properties

  • Easily corrodible
  • Can loose electrons
  • Form basic oxides
  • Have low electronativities
  • Good reducing agents

Q2. Give reasons for the following: [CBSE 2016]

(i) lonic compounds have generally high melting points.

(ii) Hydrogen is not a metal, but it has been assigned a place in the reactivity series of metals.

(iii) The galvanised iron article is protected against rusting even if the zinc layer is broken.

(iv) The wires carrying current in homes have a coating of PVC.

Ans.  

  1. There are electrostatic forces of attraction between the cations and anions in ionic compounds which are difficult to break. Therefore ionic compounds have high melting points
  2. Metals above hydrogen evolve hydrogen gas and metals below hydrogen do not evolve hydrogen when treated with an acid. That is when hydrogen has been assigned a place in the reactivity series of metals.
  3. Even if zinc layer is broken, it will preferentially oxidised because it is more reactive than iron.
  4. The wires carrying current in homes have a coating of PVC. This is because PVC is an insulating substance and protects from electric shock.

Q3. Write one example of each of the following: [CBSE 2016]

(a) Most malleable metal and most ductile metal.

(b) The best conductor of heat and the poorest conductor of heat.

(c) A metal with highest melting point and a metal with lowest melting point.

Ans. 

  1. Gold is the most malleable and ductile metal.
  2. Silver is the best conductor, whereas lead is poor conductor of heat.
  3. Tungsten has highest melting point, Mercury has the lowest melting point.

Q4. a) Define corrosion. [CBSE 2016]

(b) What is corrosion of iron called?

(c) How will you recognise the corrosion of silver?

(d) Why corrosion of iron is a serious problem?

(e) How can we prevent corrosion of iron?

Ans.

  1. It is a process in which a metal reacts with substances present in air to form surface compounds.
  2. Rusting
  3. Black layer on its surface due to formation of Ag2S.
  4. It makes the metal weak and brittle, which is serious problem.
  5. Oiling, painting, greasing, galvanisation, alloying can prevent iron from corrosion.

Q5. What are Non-metals? What are its properties?

Ans. Non-metal is a chemical element that does not have metal’s properties. They occur in liquid or gaseous states. There are very few non metals in nature and all of them are present in the periodic table.

Physical Properties

  • Poor conductors of heat and electricity
  • Non-Ductile metals
  • Brittle solids
  • Non-Sonorous

                 Chemical Properties

  • The number of electrons in the outer shell is generally 4-8.
  • Easily gain or lose valence electrons.
  • Form acidic oxides, whenever they come in contact with oxygen.
  • High electronegative elements.
  • Great oxidizing agents