Name the unit in which the calorific value of a fuel is expressed.
The calorific value of fuel is expressed in Kilojoules per kg (kJ/kg).
Explain how CO2 is able to control fires.
(i) CO2 forms a blanket around fire due to which supply of air (oxygen) is stopped.
(ii) CO2 also brings down the temperature of the fuel.
Hence able to control fires.
Which zone of a flame does a goldsmith use for melting gold and silver and why ?
A goldsmith uses the outer zone (non-luminous zone) of candle flame to melt gold and silver because it is hottest zone and has more temperature.