Question

Suggest a method to liquefy atmospheric gases.

Answer 1

by increasing pressure.
example. water can be distiled out at 50℃ by increasing pressure.
when you increas the pressure molecules of gas are come closer and become chang the state. also by decreasing temperature. 

Answer 2

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It can be achieved by either increasing the pressure or decreasing the temperature which ultimately leads to the reduction of spaces between molecules.

Thanks !!