How Temperature Scales are marked?
Now, let’s come back to our freezing and boiling point temperatures of water. To mark zero and 100 degree Celsius temperatures and other temperatures between this range the head tip of thermometer that contains mercury is dipped in water. As the temperature of water changes the level of mercury within capillary goes up or down. Initially the temperature of water is reduced so the level of mercury in capillary also goes down. The point at which water gets converted to ice is called freezing point temperature of water and the level of mercury obtained at this temperature is marked as zero degree Celsius. Then the temperature of water is increased gradually and at some particular level it starts boiling, this temperature is called as boiling point temperature of water and the level of mercury at this temperature is marked as 100 degree Celsius. Thereafter, all the other temperatures are marked at equal distance between 0 and 100 degree Celsius. This is how zero degree Celsius as freezing
