Give the working principle involved in chromatography. 

When Shashi went to Vizag with his parents, he noticed that all the fishermen store their fish inside a thermally insulated container which is filled with ice and salt. Can you give an explanation for this? 

Explain how and why usage of pressure cooker affects the cooking process. 

What is the shape of the meniscus observed when water and mercury are taken in two different capillary tubes and why? 

Evaporation can take place at any temperature, but boiling takes place at a fixed temperature. Give appropriate reasons. 

The surface of the electric bulb with a tungsten filament becomes greyish-black after being used for a long period of time. Explain the reason.