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23 Cards in this Set
- Front
- Back
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What happens when water evaporates?
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1) When water molecules evaporate, they enter air as a gas and enter spaces between air molecules.
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Is there a limit to the amount of space between air molecules?
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Yes, there is a limit to the amount of space between air molecules.
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Capacity
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The maximum amount of water vapor the air can hold.
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Can air's capacity change?
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Yes, warmer air has a greater capacity (holds more water vapor) than colder air
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Humidity
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The measurement of the amount of water vapor in the air.
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Relative Humidity
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1) expresses humidity as a percentage
2) describes how "full" the air is compared to its capacity 3) humidity of 72% means 72% of the spaces in the air are filled with water molecules 4) maximum relative humidity is 100% |
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Name 2 factors in the measurement of relative humidity.
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1) Whenever water evaporates, it absorbs heat from its surroundings
(when water evaporates, whatever it is touching will become cooler) 2) water evaporates at different rates depending on the relative humidity (the lower the humidity reading, the more rapidly water can evaporate) |
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psychrometer
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An instrument on which humidity is measured.
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As air cools...
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1) it's capacity shrinks
2) the humidity % rises 3) eventually, the humidity % will reach 100% |
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Dew Point
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If air cools and humidity % reaches 100%, air is said to have reached the dew point.
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What happens when air cools below it's dew point?
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It will no longer be able to hold all of the water vapor that it contains. Excess water vapor that no longer fits in the air will be forced to come out of the air. The further the air cools below dew point, the more of this water vapor will have to come out of the air.
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Condensation
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When air cools below its dew point and the temperature is still above freezing, excess water vapor in the air changes into little water droplets of liquid water. If this happens closer to the ground, it will stick to blades of grass, windows, etc. This is called "dew". If this occurs several feet above the ground, it will be called "fog".
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Deposition
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If the air cools below dew point and the temperature is below freezing, excess water vapor will change directly into little crystals of ice. This is called "frost".
***It is important to note that "frost" was NEVER in a liquid form*** If this happens closer to the ground, it will stick to blades of grass, windows, etc. If it occurs several feet above the ground, it will be called "fog". |
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Condensation Nuclei
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Particles of dust floating in the atmosphere. These particles may allow water droplets or ice crystals to stick to them and drift through the air on air currents.
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Fog
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Water droplets or ice crystals that float in the air several feet above the ground. If air cools slightly below dew point, fog will be "light" or "mist". If air cools well below dew point, fog will be "heavy" or "thick".
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Clouds
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1) When water droplets or ice crystals form around a condensation nuclei hundreds of feet above the ground.
2) Clouds are different from fog, dew, or frost as they can produce precipitation. |
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Temperature
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A measurement of energy. The average amount of energy of motion of each molecule of a substance.How hot or cold a substance is. Temperature is measured using a thermometer.
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Thermometer
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A thin glass tube with a bulb at one end that contains a liquid, usually mercury or colored alcohol. Liquids expand when they are heated, so the liquid travels up the tube giving a higher temperature reading. When liquids are cooled, they contract, so the liquid goes down in the tube and gives a lower reading.
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Fahrenhiet Scale
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Developed by Gabriel Fahrenheit in 1717. Commonly used in the U.S.
Freezing Point Fahrenheit: 32 degrees Boiling Point Fahrenheit: 212 degrees |
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Celsius Scale
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Developed by Anders Celsius in 1742.
Used throughout the rest of the world (not the USA). Freezing Point Celsius: 0 degrees Boiling Point Celsius: 100 degrees |
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Kelvin Scale
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Another scale for temperature measurement developed by William Thompson (Lord Kelvin) of Britain in 1848.
When a material is cooled, it looses heat, and its temperature decreases, until a point is reached where it has no more heat left to loose. At this point it is not possible to lower the temperature any further. This low temperature is called absolute zero. Lord Kelvin suggested that this absolute zero temperature be the basis of a new scale which begins with the value zero at absolute zero. At sea level on this scale, water freezes at 273 degrees, and boils at 373 degrees. |
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Temperature Range
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The difference between the high and low temperatures on a certain date.
Example: *78 degrees and 85 degrees *85 degrees-78 degrees= 7 degrees |
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Average Temperature
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The average between the high and low temperatures on a ceratin date.
Example: *25 degrees and 50 degrees *25 + 50= 75 degrees *75/2= 37.5 *rounded to 38 degrees |
