Why do we separate mixtures?

Why do we sweat ?

What is the basis for choosing a separation technique to separate mixtures ?

Why do we sweat more in summer?

Why don't we use water instead of mercury in Torricelli experiment? If we are ready to do this experiment, what length of tube is needed?

Why do we see water droplets on outer surface of a glass containing ice - cold water?

Why do we store water in matkas (earthern pots)?