7th Grade Science
The Atmosphere
Chapter 5 Study Guide
Section 1: What is weather?
 Factors that determine the weather:
o Temperature- average motion of air particles
o Wind- movement of air from area of high to low pressure
o Humidity- amount of moisture in the air
o Relative humidity – amount of moisture in the air compared to the amount the air
can hold at a specific temperature
 How is wind measured?
 Warm air holds more water vapor than cold air
 Clouds form at dew point when warm, moist air rises and condenses
 How does temperature influence the five types of precipitation?
Key terms: weather, humidity, relative humidity, dew point, fog, precipitation
Section 2: Weather Patterns
 Air masses are determined by the conditions of the area it covers
o Over water = moist air
o Over land= dry air
o Closer to poles = cold air
o Closer to equator = warm air
 Fronts form when air masses meet
 Four types of fronts:
1. Warm- warm air moves in slowly over cool air; creates days of wet weather
2. Cold- cool air moves in quickly and forces warm air up; creates violent storms
(thunderstorms, tornados)
3. Occluded- warm air is cut off by cool and cold air and forced up
4. Stationary- warm and cool air at standstill
 What do all four types of fronts have in common?
 High air pressure = nice, fair weather because it is difficult for air to rise and form clouds
 Low air pressure = cloudy, stormy weather because air rises easily to form clouds
 What causes thunder and lightning?
 Tornados form from areas of low pressure caused by swirling winds
o Tornados produce the strongest winds and cause the most destruction
 Hurricanes form from swirling winds over tropical oceans (warm, moist air)
 Blizzards form during freezing temperatures when snow falls to the ground at fast speeds
o Dangerous because decreases visibility
Key terms: air mass, front, tornado, hurricane, blizzard
Section 3: Weather Forecasts
 What instruments are used to forecast the weather?
 Meteorologists gather data from the surface and in atmosphere using instruments to
make weather maps
 Station models indicate weather at a particular location
 Isobars vs. isotherms
 Isobars close together indicate strong winds
Key terms: meteorologist, station model, isotherm, isobar
Possible short answer/essay topics:
1. Weather factors
2. Fronts
3. Severe Storms