Presentation on theme: "What is Air? It’s a GAS! Mostly Nitrogen= 78% Oxygen = 21% Argon = about 1% Trace amounts of other gases Composition of Earth’s Atmosphere."— Presentation transcript:
What is Air? It’s a GAS! Mostly Nitrogen= 78% Oxygen = 21% Argon = about 1% Trace amounts of other gases Composition of Earth’s Atmosphere
Volume Define system Molar Volume of any gas at STP = 22.4 L
Amount of Gas 1 Molar Volume (22.4 L) = 6.02 x particles (Avogadro’s number) 1 Mole
Pressure The force exerted by the weight of air molecules Atmospheric pressure = 14.7 lbs/in 2
Behavior of Gases ParametersDefinition Amount of gasNumber of particles, mass VolumeAmount of space occupied TemperatureAverage kinetic energy of the particles PressureForce exerted
Principles of Meteorology Foldable Envelope fold Add information at each of 4 stations
Station 1 Temp vs. Volume Charles’ Law (closed system, constant P) As temperature decreases, volume decreases As the air cools it condenses.
Station 2 Temp Vs. Density When temperature decreases, density increases As cooler air condenses it becomes more dense and sinks forcing warmer air upwards.
Station 3 Volume and Pressure Boyle’s Law (closed system, constant T) As volume increases, pressure decreases As warm air rises, it expands (volume inc). As volume increases, pressure it exerts decreases Warm fronts = low pressure Cold fronts = high pressure
Station 4 – Pressure and Temperature Gay-Lussac’s Law As pressure decreases, temperature decreases As the pressure of the rising air decreases, the air cools. The moisture in the air condenses to form clouds.
When 3 factors change… Combined Gas law P 1 V 1 = P 2 V 2 T 1 T 2 VOLUME increases (rising air) PRESSURE decreases (Boyle’s Law) TEMPERATURE decreases (Gay-Lussac’s Law)
Cold Front Cold air mass advances toward warm air mass Cold air mass slides under warm air mass Forces warm air to rise and cool rapidly Can produce rapid temperature drops and severe weather Forms cumulus clouds Strong cold front forms cumulonimbus clouds, storms, tornado, snow squalls Low humidity
Warm Front Warm air advances toward cold air mass Warm air slides over cold air Front moves more slowly with a gentle rise in temperature Produces less severe weather, steady precipitation lasting for days Leading edge forms high cirrus clouds at first, then cirrostratus, altostratus, and nimbostratus later High humidity
Condensation Cool air causes water VAPOR to condense - contains less moisture than warm air Cool air causes water VAPOR to condense - contains less moisture than warm air Relative humidity - a measurement of the amount of water vapor in the atmosphere compared to the amount of moisture that can be in gas form at a given temperature. Relative humidity - a measurement of the amount of water vapor in the atmosphere compared to the amount of moisture that can be in gas form at a given temperature. Dew point - the temperature to which air would have to be cooled to become “saturated”. Once the air is cooled enough, the water vapor condenses to form a liquid. Dew point - the temperature to which air would have to be cooled to become “saturated”. Once the air is cooled enough, the water vapor condenses to form a liquid.
Rain and Clouds
There is a fine line Precipitation and cloud formation is all about states of matter When water evaporates at the surface, it is an invisible gas. As the water vapor (gas) rises, it cools and condenses to a liquid droplet. Clouds are liquid! (condensed water vapor) Rain is larger droplets of liquid that fall to the ground.
Careful explanation Air does not “hold” water. So what can we say: Air is a mixture. Water vapor is commonly found in air. If the air is cold enough, water cannot remain in gas state and becomes liquid. The size of the drops and amount of water will determine if it can stay aloft or if the force of gravity is enough to pull the liquid to the ground.
Atmosphere Misconceptions: The atmosphere traps radiation. The atmosphere “re-radiates” the radiation back to Earth. The atmosphere works like a greenhouse, blanket or car.- NO! True Statement- Radiation is absorbed by the atmosphere and radiates back to the Earth. Two times more heat comes from our atmosphere than the Sun. The atmosphere promotes convection instead of preventing convection.
Weather Station Temperature Barometric pressure Relative humidity Light Anemometer UVA/UVB