Q16 of 27 Page 1

a. How will you show experimentally that metals are good conductors of heat?

b. Describe the extraction of Mercury metal from its ore Cinnabar (HgS).

a. Metals are good conductors of heat as well as electricity.

1. The main reason for the conduction in metals is the presence of an excess of free electrons.


2. Whenever the metal heat or electricity is applied to the metals, the free electrons get excited and accelerate at some velocity.


3. During this movement, the electrons transfer their energy to other electrons, and hence the metals conduct.


Experiment:


Apparatus: One metal rod, heat source [candle, Bunsen burner etc]


Procedure:


1. Switch on the heat source if it is power by electricity or else take a candle and light the candle. Once the candle is lit, hold the metal rod by pointing its one end on the flame of the candle.


2. Within a few seconds or minutes, you will feel the heat at the other end of the rod, and after some time the rod gets very hot.


3. This simple experiment proves that metals are good conductors of heat as the heat is spread over the entire rod within a few minutes. Another technique which can be employed is that apply wax at one end of the rod and fix a pin to it and keep another part of the rod over the heat source for some time.


4. After some time it will be observed that the wax begins to melt and the pin falls which proves that metals are good conductors of heat.



b. The primary ore of mercury metal is cinnabar which mercuric sulphide by its chemical structure.


1. Mercury can be easily separated from its ore by roasting the ore of mercury.


2. Roasting is a process in metallurgy where the ore is heated to very high temperature in the presence of oxygen to separate the metal from the ore. The roasting reaction is as follows:


HgS + O2→ Hg + SO2


3. During the roasting, the ore is heated to very high temperature because of which mercury metal in its pure state gets evaporated and can be collected in a condensing column.


4. If the mercury contains its oxide form after roasting it can be reduced with the help of any reducing agent to obtain a pure mercury metal.



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a) Draw the diagram of the female reproductive system and match and mark the part(s):

i) Where the block is created surgically to prevent fertilization.


ii) Where CuT is inserted?


iii) Inside which condom can be placed.


b. Why do more and more people prefer to use condoms? What is the principle behind the use of condoms?