Available Answers

1. 1.

   Choose the correct answer:

   1. An element is made up of 
      1. only one kind of atoms
      2. two kinds of atoms
      3. three kinds of atoms
      4. many kind off atoms
   2. Metalloids are elements that exhibit properties of
      1. metals
      2. non-metals
      3. intermediate between metals and non-metals
      4. none of these
   3. The only non-metal which is a good conductor of electricity is
      1. tungsten
      2. graphite
      3. zinc
      4. oxygen
   4. A molecule of sodium chloride contains
      1. one atom of sodium and two atoms of chlorine.
      2. two atoms of sodium and one atom of chlorine.
      3. one atom of sodium and one atom of chlorine.
      4. one atom of sodium and three atoms of chlorine.
   5. The symbol for sulphur is
      1. S
      2. S₂
      3. S₄
      4. S₈
   6. Mist is a heterogeneous mixture of
      1. solid in gas
      2. liquid in gas
      3. gas in liquid
      4. gas in gas
   7. Common salt can be obtained from its solution by the process of
      1. decantation
      2. winnowing
      3. evaporation
      4. centrifugation
   8. During the process of distillation, the pure liquid is collected in the 
      1. distillation flask
      2. water condenser
      3. separating funnel
      4. receiver
   9. During the process of distillation, the pure liquid is collected in the
      1. winnowing
      2. sieving
      3. sublimation
      4. evaporation
   10. Which of the following methods of separation is used to separate cream from milk?
       1. Distillation
       2. Evaporation
       3. Centrifugation
       4. Crystallisation
2. 2.

   Fill in the blanks:

   1. Water is a compound made up of two atoms of ________________ and one atom of ________________.
   2. An element is a ________________ substance.
   3. The symbol of sodium is ________________.
   4. Metals are ________________ of heat and electricity.
   5. Common salt is a compound of ________________ and ________________.
   6. Husks are removed from grains by the process of ________________.
   7. The liquid collected after filtration is called ________________.
   8. The solutions of two immiscible liquids are separated by using a ________________.
   9. Ammonium chloride can be separated from a mixture of ammonium chloride and sand by ________________.
   10. Components of two ________________ liquids are separated by fractional distillation.
3. 3.

   Write True (T) or false (F) against the following statements:

   1. S₈ and P₄ are diatomic molecules.
   2. Noble gases are highly reactive.
   3. Smoke is a homogeneous mixture of a solid in gas.
   4. A mixture of ammonium chloride and common salt is separated by sublimation.
   5. Centrifugation involves rotating a solution at a very high speed to separate suspended solid particles from it.
4. 4.

   Write down the symbol / formulae of the following elements/compounds:

   1. Carbon	2. Ammonia	3. Copper sulphate
   4. Sodium	5. Calcium oxide.	6. Acetic acid
   7. Tungsten	8. Water	9. Mercury
   10. Iron oxide	11. Zinc	12. Nitrous oxide

    

5. 5.

   Name the following elements/compounds:

   1. CaCO3	2. H	3. Au
   4. Mg	5. P	6. SO3
   7. Sn	8. SiO2	9. Ca(OH)2

    

6. 6.

   Define elements. What are the different kinds of elements?