Answers to Worksheet 3 � Elements, Compounds & Mixture

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					Answers to Worksheet 3 – Elements, Compounds & Mixture
Science(Chemistry) Theory Workbook Pg 20 to 18

Check It ( Pg 20 to 12)

1. A       2. B   3. B   4. A    5. B   6. B      7. C    8. B   9. C   10. A


              A : Element        B : Compound            C : Compound

              D : Element        B : Compound            C : Mixture

12a.        A chemical substance formed from two or more elements
            chemically combined together in a fixed ratio.
      b.    Zinc glowed white-hot because of a chemical reaction with
            chlorine and a new substance which is a white solid was
      c.    Unlike zinc (in the mixture), the compound zinc chloride will
            not conduct electricity. It also cannot be converted back to
            zinc and chlorine by physical means.

      Practice Question ( Pg 23 to 24 )
      a) A : Solid         B : Gas           C:    Solid          D:    Solid
         E : Solid         F : Gas           G:    Liquid

      b)   C
      c)    Process of a solid changing directly into gas without going
           through the liquid state.
      d)   F
      e)   A2, C4 and D8

Test It ( Pg 24 to 26 )

1.     C ( C, Fe and Zn, only made up of single type of atoms)
2.     C ( Metals in solid and molten states conduct electricity)
3.     B ( copper is a metal with all the properties)
4.     A ( Nitrogen is made up of diatomic molecules, N2, is in
            gaseous state at r.t.p)
5.     D ( one molecule has 2C,4H and 2O atoms, 2 x 8 = 16 atoms )
6.     D ( formula shows 4 elements – C, H, O and Na, and 11 atoms )
7.     C ( still have unreacted elements)
8.     D ( all possible except “1” , metals and metals do not react)
9.     D ( sugar solution is impure, is a mixture )

10.    From the list , the mixtures are air, brass, steel, salt water
                       and petrol, the compounds are common salt, water
ai)    air (carbon dioxide & water are compounds and the elements
            are nitrogen ,oxygen, and the rare gases-argon, neon,
            helium ….)
ii)    air, petrol or salt water ( any one )
iii)   brass ( copper and zinc, both metals)
iv)    steel ( iron a metal and carbon a non-metal)

bi)    water ( hydrogen and oxygen)
ii)    water

11a) i. Al – Aluminium ii. Mn - Manganese            iii. Ne - Neon
  b) i. Chlorine – Cl         ii. Mercury – Hg       iii. Oxygen - O
  c) i. Osmium               ii. Hydrogen
  d) Osmium
  ei) Mercury, manganese, osmium, aluminium
    ii) Bromine, chlorine, neon, oxygen, hydrogen
  fi) Mercury
   ii) Bromine


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