1. 4.2-4.3

2.  The atmosphere is a layer of gases that wraps around
Earth like a blanket
 It holds in heat, contains the air we breathe, protects living
things from the sun’s harmful radiation, and helps the planet
recycle its water supply
 The atmosphere is made up of nitrogen and oxygen with
small amounts of carbon dioxide and water vapor
 Earth is the only planet who’s atmosphere is formed of these
gases
 Carbon dioxide is a greenhouse gas that absorbs Earth’s heat
and keeps the planet warm
 Water vapor is a greenhouse gas that plays an important role
in weather
 Earth’s atmosphere is also made up of particles like soil,
pollen, grains, and soot that help form clouds

4. Weather: the state of the atmosphere at a certain
place and time
 It changes all the time
 We can observe weather by measuring properties of the
air like temperature, humidity, air pressure, and wind
These can also help us predict weather

5. Temperature is how hot or cold something is

6. Humidity: the amount of water vapor air can hold
 Warm air holds more water vapor than cool air
 Air that is humid holds a lot of water vapor
 Humid air is more likely to produce clouds and
precipitation

7.  Air has weight
 We live at the bottom of Earth’s atmosphere, so there is a lot of
air above us
 The force of the weight of the air pushing down on us is air
pressure
 Air pressure is not the same everywhere
 Temperature affects air pressure
 Low air pressure
 Air gets warmer  gas particles get farther apart and rises
 Rising air presses down with less force and creates a low area of
pressure
 Clouds form where low pressure forms
 High air pressure
 Air gets cooler  gas particles get closer together and sink
 Sinking air presses down with more force and creates a high area of
pressure

8. Wind is the movement of air from areas of high
pressure to areas of low pressure
When the difference of pressure great, the wind blows
faster
When the difference of pressure is small, the wind
blows slower