Page 46 - Science Class 08
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                i Minerals have four classes–metals, metalloids, non-metals and gems.
                i Minerals are quite different from fuels as they are formed from non-living materials while
                    fuels are formed from dead living matter.
                i Metals occur in their ores along with other metals, but a few of them occur in free state.

                i The impurities in a free-state mineral are called gangue.
                i Extraction of metals in pure form involves three steps–concentration, reduction and refining.
                i Chief  physical  properties  of  metals  are  physical  state,  lustre,  ductility,  malleability,
                    conductivity, hardness, reflection capacity, high specific gravity and boiling points and that
                    they are sonorous.
                i Metals react with oxygen, air, water and acids in different ways. They display replacement
                    reactions too.

                i Metals are very useful especially in this age of Science.
                i Corrosion is wearing away of a metal slowly due to formation of compounds on its surface.
                i Corrosion of metals takes places due to the reactions– oxidation and reduction.

                i Corrosion is of two types– local and uniform. Uniform corrosion is mild, but local corrosion
                    is very severe.
                i Coatings of paints, grease and processes of electroplating, alloying and galvanizing keep off
                    corrosion.


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              A.   Tick (3) the correct op on.
                  1.   Iron acts with copper sulphate and changes its blue colour to:
                      (a)  yellow                                     (b)  red
                      (c)   green                                     (d)  white

                  2.   The colour of zinc sulphate is:
                      (a)  pink                                       (b)  white
                      (c)   red                                       (d)  no colour
                  3.   Corrosion takes places due the processes of:

                      (a)  reduc on                                   (b)  oxida on
                      (c)  both (a) & (b)                             (d)  none of these
              B.   Write the correct term for.

                  1.   the material from which minerals are formed            :    __________________________
                  2.   the material from which fuels are formed               :    __________________________
                  3.   the form in which most metals occur                    :    __________________________
                  4.   the metals whose extrac on is difficult and costly       :    __________________________

                  5.   the technology of obtaining metals from their ores  :       __________________________


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