Why are the published values of the boiling points of substances always taken at 1 atm?
seldom does one boil something at other than standard pressure, or close to it.
The published values of boiling points are typically taken at 1 atm (atmospheric pressure) for several reasons:
1. Standardization: Using a standard pressure, such as 1 atm, allows for consistent and comparable data across different substances. It simplifies the comparison of boiling points and facilitates the organization and analysis of data.
2. Practicality: 1 atm is approximately the average atmospheric pressure at sea level. Since most laboratory experiments and measurements are conducted at or near sea level, it is convenient to report boiling points at this pressure. It is easily replicable in experimental conditions.
3. Simplification: Different substances have different boiling points, and the boiling point of a substance can vary with changes in pressure. By using a fixed pressure, it eliminates the need to consider pressure variations and allows for easier comparison among substances.
4. Interpretation: Boiling point is defined as the temperature at which a liquid's vapor pressure equals the atmospheric pressure. By reporting boiling points at 1 atm, it provides a reference point and allows us to infer how the substance behaves under standard atmospheric conditions.
It is worth noting that boiling points can vary under different pressures. Additionally, if the substance is influenced by other factors such as altitude or the presence of impurities, the boiling point may deviate from the values published at 1 atm.
The published values of boiling points are typically taken at 1 atmosphere (1 atm) because it is the most commonly used standard pressure for reporting and comparing boiling points. The boiling point of a substance is the temperature at which its vapor pressure equals the atmospheric pressure.
When a liquid is heated, its vapor pressure increases until it reaches the pressure of the surrounding atmosphere. At this point, bubbles of vapor form within the liquid, and the liquid starts boiling. The boiling point is the temperature at which this vapor pressure equals 1 atm.
Using a standardized pressure of 1 atm simplifies the comparison of boiling points between different substances. It provides a consistent reference point for scientists and researchers to compare and analyze the behavior of various substances under the same conditions. By keeping the pressure constant, it allows for a direct comparison of the boiling points, which is important for various scientific, industrial, and practical applications.
To measure the boiling point of a substance, researchers typically use an apparatus called a distillation setup. This setup has a thermometer (usually a calibrated glass bulb) immersed in the liquid, and the pressure within the apparatus is adjusted to 1 atm. The temperature at which the liquid starts boiling, as indicated by the thermometer, is then recorded as the boiling point.
It is worth mentioning that the boiling point of a substance can vary with pressure. For example, at higher altitudes where atmospheric pressure is lower, the boiling point of a substance will be lower. Conversely, at higher pressures, the boiling point will be higher. However, for consistency and comparability, the values published in reference materials are commonly reported at a pressure of 1 atm.