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Science Study Guide
Chapter 3 – Weather
Vocabulary
humidity – the amount of moisture in the air
weather – the condition of the atmosphere at a certain place and time
climate – an areas pattern of weather over a long period of time
water cycle – the movement of water from Earth’s surface to the atmosphere and back to Earth
evaporation – the process by which a liquid changes into a gas
condensation – the process by which a gas changes into a liquid
precipitation – water that falls to Earth as rain, snow, sleet, or hail
water vapor – the gas form of water
meteorology – the study of weather
humidity – the amount of water vapor in the air
cumulus – puffy white clouds that indicate fair weather, but can grow into a rain cloud
cumulonimbus – tall dark rain clouds that indicate a storm is coming
barometer – an instrument for measuring air pressure
hygrometer – an instrument for measuring humidity
anemometer – an instrument for measuring wind speed
thermometer – an instrument for measuring air temperature
rain gauge – an instrument that measures rainfall
wind vane – an instrument that tells the direction of the wind
Concepts
*The water cycle begins with energy from the sun. The steps are evaporation, condensation, and
precipitation. The rainfall returns to rivers, lakes and oceans as runoff, where the process starts over.
*Water freezes at 0 degrees (C) or 32 degrees (F)
*Water boils at 100 degrees (C) or 212 degrees (F)
*As water heats up, it evaporates and changes from a liquid to a gas and forms water vapor. When the
water vapor cools, it condenses and changes from a gas back to a liquid forming clouds.
*As ice cubes in a glass of water warm up, the ice changes from a solid to a liquid. As the liquid continues
to heat, the liquid will change to a gas due to evaporation.
*Before a thunderstorm, air pressure drops. A barometer shows this and can help predict storms.
*Hail is formed when water droplets freeze as they pass through very cold air.
*On a weather map, cold fronts are indicated by a blue line with triangles. Warm fronts are indicated by a
red line with half circles.
*When a cold front passes over an area, the weather will be cooler and drier. When a warm front passes
over an area, the weather will be warmer and more humid.
*When water vapor condenses near the ground, fog is formed.
*Snow is produced when temperatures are low and the air is filled with water vapor.