Every now and again one of those molecules is going

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every now and again one of those molecules is going to escape out into the air space (evaporation); over time, we’re building up more and more of those molecules in the air space; at first, we don’t have very many and so as those molecules are moving around randomly in that space, every now and again one of those molecules is going to collide back to the water (condensation); the rate at which those molecules are escaping from the water is going to be much higher than the rate at which they collide simply b/c we don’t have very many of them yet up there (every 2 that’s escaping, only 1 is returning); over time, we get more water vapor molecules in the air, but with more of them in the air more often they’re going to collide back to surface (every 2 escaping, 2 are returning) - 3rd – no change over time in how many water vapor molecules there are in air space b/c it’s in steady state (saturation) - undersaturation – when we don’t have as many molecules as we could have (2 nd ); more molecules escaping than returning - water vapor content - what happens if temperature increases? - undersaturated (more evaporation can take place if water is available) - less vapor pressure in air than I could have at saturation - net evaporation - what happens if temperature decreases? - supersaturated (condensation/deposition will take place) - more water vapor molecules than saturation - net condensation - what happens if you add more water vapor? - supersaturated (condensation/deposition will take place)
- at what temperature would the air become saturated? - 10 C - not adding/removing water vapor, just changing temperature - cloud formation - clouds form when air becomes saturated and water droplets or ice crystals form - to saturate air, we can: - add water vapor (by more evaporation over lakes/ocean)(water has high specific heat, so adds heat/moisture) - cool down the air (by forcing the air to rise higher in the atmosphere)(lift air up into atmosphere by lifting it up over mountains and then the air sinks down and warms up) - Be able to describe and explain the forces acting on a raindrop as it falls through the atmosphere (i.e. weight and drag) and what influences them. Be able to explain how the weight and drag of a raindrop/ice crystal will affect its terminal velocity.
- why must raindrops/ice crystals grow bigger to fall?

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