Boiling is a process of steam formation, that is transition of substance of liquid state to gaseous state. It differs from evaporation in the much bigger speed and rough course. Any pure liquid boils at a certain temperature. However depending on the external pressure and impurity temperature of boiling can significantly change.
It is required to you
- - flask;
- - studied liquid;
- - cortical or rubber stopper;
- - laboratory thermometer;
- - curved tube.
Instruction
1. As the simplest device for determination of temperature of boiling it is possible to use a flask with a capacity about 250-500 milliliters with a round bottom and a wide throat. In it pour the studied liquid (it is desirable within 20-25% of vessel volume), cork a mouth cortical or rubber with two openings. Into one of openings insert the long laboratory thermometer, into another – the curved tube playing a role of the safety valve for removal of vapors.
2. If it is necessary to determine temperature of boiling of pure liquid – the tip of the thermometer has to be near it, but without concerning. If it is necessary to take solution boiling temperature – the tip has to be in liquid.
3. By means of what source of heat it is possible to heat a flask with liquid? It can be a water or sandy bath, the rangette, the gas burner. The choice depends on properties of liquid and estimated temperature of its boiling.
4. Right after that as boiling process will begin, write down temperature which is shown by mercury stem of thermometer. Observe indications of the thermometer of at least 15 minutes, writing down indications each several minutes, at regular intervals. For example, measurements were taken right after the 1st, 3rd, 5th, 7th, 9th, 11th, 13th and 15th minute of experience. In total they were 8. After the end of experience calculate the average arithmetic temperature of boiling on a formula: tcp = (t1 + t2 + … +t8)/8.
5. At the same time it is necessary to consider very important point. In all physical, chemical, technical reference books the indicators of temperature of boiling of liquids are given with a normal atmospheric pressure (760 mm Hg). It follows from this that along with measurement temperatures should be taken by means of a barometer atmospheric pressure and to make the necessary amendment to calculations. Just the same amendments are provided in tables of temperatures of boiling for various liquids.