Questions and Answers
The units are sometimes called “degrees Kelvin’’; however, the correct SI terminology is “Kelvins,’’ abbreviated K.K = °C + ____. TEMPERATURE SCALE
273.15
____ temperature scale related to the Fahrenheit (°F) scale and both scales have the size of temperature.
Rankine
The freezing point of water occurs at 491.67°R, whereas it boiling point occurs at 671.67°R.°R = °F + ____.
459.67
VAPOR PRESSURE – the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a system.VAPOR PRESSURE Suppose the air parcel is near sea level and the air pressure inside the parcel is 1000 millibars (mb).The total air pressure inside the parcel is due to the collision of all the molecules against the walls of the parcel.In other words, the total pressure inside the parcel is equal to the sum of the pressures of the individual gases.Since the total pressure inside the parcel is 1000 millibars, and the gases inside include nitrogen (78 percent), oxygen (21 percent), and water vapor (1 percent), the partial pressure exerted by nitrogen would then be 780 mb and, by oxygen, 210 mb.The partial pressure of water vapor, called the actual vapor pressure, would be only 10 mb (one percent of 1000).
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The partial pressure of water vapor, called the actual vapor pressure, would be only ____ mb (one percent of 1000).
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The correct SI terminology is “Kelvins,’’ abbreviated ____.K = °C + 273.15 TEMPERATURE SCALE
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The units are sometimes called “degrees Kelvin’’; however, the correct SI terminology is “____,’’ abbreviated K.K = °C + 273.15 TEMPERATURE SCALE
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The freezing point of water occurs at ____°R, whereas it boiling point occurs at 671.67°R.°R = °F + 459.67
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VAPOR PRESSURE – the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a system.VAPOR PRESSURE Suppose the air parcel is near sea level and the air pressure inside the parcel is ____ millibars (mb).
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Since the total pressure inside the parcel is 1000 millibars, and the gases inside include nitrogen (78 percent), oxygen (21 percent), and water vapor (1 percent), the partial pressure exerted by nitrogen would then be ____ mb and, by oxygen, 210 mb.
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Study Notes
Vapor Pressure and Humidity
- Actual vapor pressure measures the air's actual water vapor content, while saturation vapor pressure measures the air's total capacity for water vapor.
Relative Humidity
- Relative humidity is given as a percent and represents the ratio of the air's actual water vapor content to its total capacity.
- 50% relative humidity means the air contains half the amount of water vapor needed for saturation.
- 100% relative humidity means the air is saturated with water vapor.
- Relative humidity above 100% is supersaturated.
Dew Point
- The dew point is the temperature at which air becomes saturated with water vapor, causing condensation.
- Dew point depends on air pressure and water content.
- When air is cooled below its dew point, airborne water vapor condenses to form dew.
- Dew point is affected by air humidity, with high humidity resulting in a higher dew point.
Humidity and Temperature
- Colder climates tend to have lower humidity levels than warmer weather.
- Warmer air can hold more water vapor than cold air, resulting in higher humidity levels in summer.
- High humidity makes temperatures feel hotter due to the difficulty of sweat evaporation from the skin.
Temperature Scales
- The Kelvin scale is an absolute temperature scale, where K = °C + 273.15.
- The Rankine temperature scale is related to the Fahrenheit scale, where °R = °F + 459.67.
Vapor Pressure and Air Composition
- Vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases.
- In a system with a total air pressure of 1000 mb, the partial pressure of water vapor (actual vapor pressure) is only 10 mb, due to its low concentration in the air.
