Chapter No 16 Chemistry Class 10 Notes
Q.1: Define mineral, ore, native metal, compound metal and gangue? Ans:
Mineral:
"An a naturally occurring substance present in rocks and ground that has its own chemical composition is called
mineral." e.g. diamond, quartz, garnet etc.
Ore:
"A type of mineral from which metal is obtained is called ore." OR Impure form of metal is called ores. e.g. hematite, bauxite, chalcocite etc.
Native metal:
"A
metal in a free state is called native metal."
Compound metal:
"A metal in the combined state is called compound metal.
It is also called mineral"
Gangue:
"The
unwanted impurities present in an ore are called gangue."
Q.2: Define metallurgy. What are its steps?
Ans: Metallurgy:
"The art and science of making metals and alloys
from their ores is called metallurgy." OR
"The extraction of metals from their ore and
conversion of them to alloys is called metallurgy."
Basic metallurgical operations/steps:
During metallurgy the following general steps are
carried out which are tailed basic metallurgical operations:
- Mining
- Grinding and crushing
- Concentration
- Roasting and calcination
- Smelting and reduction
- Electro-refining
Q.3: Describe the basic metallurgical operations in
detail.
Ans: Basic metallurgical operations:
Basic metallurgical operations are the various physical
and chemical processes by which metals are not
only extracted from their ores but also made them suitable for use. Metals are
extracted from their ores by different
methods.
The selection of the method
depends on;
a. Type of ore i.e. oxide, carbonate
etc.
b. Reactivity•of metal
c. Nature of gangue present in the ore.
During
metallurgy the following general steps are carried out which are called basic metallurgical operations:
i. Mining
ii. Grinding and crushing
iii.
Concentration
iv. Roasting and calcination
v. Smelting and reduction
vi. Electro-refining
They're the detail is given below:
1.Mining:
Extracting ores from the ground by digging the earth is
called mining.
2.Concentration:
The ore contains a large amount of gangue or useless rocky
portion. In order to remove a sufficient
amount of gangue, the concentration of ore is carried
out. Various methods are used for concentration of ore these include grinding and crushing, gravity separator, froth
floatation process etc. The detail is described below:
a.Grinding and crushing:
The ore obtained by mining consists of large pieces. In this step, the ore is
converted to small pieces with the help of grinders and crushers. These small pieces are then converted into a fine powder
with the help of ball mill or stamp mill. This
process is called pulverization
b.
Gravity separation (Hydraulic washing):
This method is based on the difference in
densities of ore and gangue. In this method, the ore containing
gangue is poured over a hydraulic classifier.
The hydraulic classifier is a vibrating inclined table with grooves. Then a jet of water is allowed to flow over the ore and
gangue. The ore particles are denser, they settle
in grooves while the lighter gangue particles
are washed away.
