Module 5 (Humidity and Condensation)

1. What is meant by the terms: evaporation, condensation, and precipitation?

Evaporation: phase change from liquid to gas

Condensation: phase change from gas to liquid

Precipitation: phase change from water vapor to liquid

1. What do the terms net evaporation and net condensation mean, with respect to a jar of water? What would happen to the liquid water level in a jar for each of these conditions?

Net evaporation: # evaporating molecules are greater than condensing molecules. 

Net Condensation: # of condensing molecules are greater than evaporating molecules

1. What must be true about the amount of evaporation and condensation for the air to be “saturated?”

The number of evaporating and condensing molecules must be equal.

1. Why does blow drying cause your hair to dry?

Because increased air molecules and hot temperatures increase evaporation rate.

1. How does air temperature affect the rate of evaporation of water?

Warmer temperatures will excite water molecules, increasing kinetic energy and evaporating faster.

1. What is the meaning of cloud-condensation nuclei (CCN)? What are three examples of substances that act as CCN?

Water molecules need to stick to something on a surface, these are called cloud condensation nuclei. Examples: dust, sand, salt. 

1. Why can warm air “hold” more water vapor than cold air?

Because warm air is less dense with more space allowing for vapor to fill those spaces. Unlike cold air which is more dense and converts air into liquid.

1. What does relative humidity tell one about saturation? How can it be defined, in terms of water vapor content and water vapor capacity?

Relative humidity: ratio of water vapor in air to the amount that it can hold in that temperature and pressure. RH is high means high levels of saturation.

1. What is the definition of dew point temperature? How is it related to the amount of water vapor in the air?

wet bulb temperature is the temp that the air would need to be cooled for saturation to occur, assuming no change in air pressure or water vapor content

1. What is the definition of heat index? For a given temperature, as dew point increases, what happens to the value of the heat index? Why?

How temp feels when humidity and air temperature are combined. As dew point increases, temp increases because air is already saturated so sweat evaporation becomes more difficult.