Why do surgeons often spray some ether on the skin before performing minor surgery?
Quite often doctors spray ether on a portion of skin the before performing minor surgery. The reason being that a ether has very low boiling point (308 K). Therefore, it evaporates quite rapidly. The heat energy needed for evaporation is taken from the skin. As a result, the temperature of the skin becomes so low that it almost becomes numb. Due to this numbness, the patient does not feel much pain when a minor cut is made in the skin in order to perform surgery. Similarly, when a player gets injured during a game, ethyl chloride on the injured portion of the body. Since the boiling point of ethyl chloiide (285.5K or 12.5°C) is very low, it quickly evaporates. The heat energy needed for evaporation is taken from the skin. By losing heat, temperature of the skin becomes so low that it almost becomes numb. Due to this numbness, the player does not feel much pain.
