Question

How are gas liquefied? Name a gas which can be solidified and called dry ice.

Answer 1

Gases are liquefied by lowering the temperature and applying huge pressure.
Carbon di oxide in the solid state is called dry ice.

Answer 2

There are two methods to liquefy a gas.

#By decreasing the temperature: By decreasing temperature,the kinetic energy of gas molecule reduces and settle down to form liquid.

#By increasing pressure: Movement/kinetic energy of gas molecule is suppressed,and made to settle down.

#The other method is doing both the above method together [its easier]

The temperature below which gases are liquefied are called critical temperature.
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Some of the gases can be solidified,under extreme pressure and very low temperature.

The gases that form dry ice is carbon dioxide gas when solidified.