Paheli had bought a new bottle of from the market. She tried to open the metal cap to taste it but could not do so. She then took a bowl a bowl of hot water and immersed the upper end of the bottle in it for five minutes. She could easily open the bottle now. Can you give the reason for this?
Paheli could do so because of the reversible change occurring in the metal cap, on the application of warm water. When Paheli first tried, the metal cap was fit tightly on the bottle. On immersion in hot water, the metal expanded and the cap became loose, making it easy for her to open the cap.
This expansion of metal on heating is a reversible change, and the metal cap will come back to its original size on cooling.