Chapter #4 Flashcards
(20 cards)
How does the thee states of water molecules differ?
Gas - molecules move around freely, mixing with other atoms
Liquid - water molecules are closer together, bump each other consistently, more dense than ice
Solid - molecules arrange themselves in pattern, molecules able to vibrate but not move around freely
Three factors that influence rate of evaporation?
- Water temperature
- Wind speed
- Moisture content of air above the water surface
Why condensation process more efficient when colder?
Warm air- fast moving water molecules are so fast that they bounce away from nuclei
Cold- slow water molecules, therefore have time to stick to water molecules
What is the difference between “actual vapor pressure (e)” and “saturation vapor pressure (es)”?
Actual vapor pressure - total or current vapor content
Saturation vapor pressure - how much water vapor is necessary to make air saturated or the amount of air that the current air can hold at a time
Saturated - 100% relative humidity
Unsaturated - less that 100% relative humidity
What does “saturation vapor pressure” depends on?
Air temperature because warmer air can hold more water vapor
What does”relative humidity” represent?
Ratio of the water vapor’s current content to its potential capacity
Why when “Relative Humidity is given, it is important to know the air temperature
A high relative humidity (RH) value in cold air mass could actually contain less actual water vapor than a low RH value in a warm air mass
(see example in review slide)
Two ways relative humidity can be changed
- Changing the air’s water vapor content while holding the temperature constant
- Changing the air temperature with no change in water vapor content
During a summer day, why does the relative humidity values change significantly while the amount of water vapor remain constant?
Relative humidity tells us how close the air is being saturated at a given temperature
What is “dew-point temperature”?
Temperature at which air would have to be cooled (with no change in air pressure of moisture content) for saturation to occur.
How is the difference between dew-point temperature and air temperature (dew-point depression) related to the relative humidity?
The difference could indicate whether the relative humidity value is low or high (if RH low, two are far apart)
Calculate relative humidity using dew point and temperature
RH = e/es X 100%
“Wet-bulb temperature”
Lowest temperature that can be reached by evaporating water into the air
“Wet-bulb depression”
Temperature difference between wet bulb and dry bulb (air temperature)
Instrument used for measuring atmospheric moisture
An aspirated or sling psychrometer
Why it takes longer to cook vegetables in the mountains than at sea level
Lower pressures lower the boiling point, so it would take longer
What does the relative humidity value tell us?
How close an air mass is to saturation (100% humidity)
What dew-point temperature tells us
Identifies how much water vapor is available
Why air is less dense on a hot, dry day
Humid air weighs less than dry air
Why do hot, humid days feel warmer than dry days
the evaporation rate from our bodies will be slower, so the sweating process is not as effective
