Density
Everything in the world is made of molecules. These molecules move differently
depending on their state - solid, liquid, or gas.
http://www.harcourtschool.com/activity/states_of_matter/
The density of solids does not change. Solids
will keep their shape even when moved.
The density of liquids changes slightly. Liquids
will change shape, but are still bound together. If you spill a glass of water
the water will change shapes and puddle, but the water will remain together.
The molecules in gases are not bound at all.
They are free to move about and will only stop when they are confined to a
container or by gravity.
Atmospheric Pressure
Atmospheric pressure is a little difficult to
understand because it can’t be seen, heard, smelled, or felt. However, it is
very important on the weather. Atmospheric pressure is the force the
atmosphere pushes on the objects located within it.
The reason we don’t feel this pressure is
because our bodies have enough gases within them that we push back on the
atmosphere with an equal force.
When the atmosphere presses down with more force, we say that it is a
high pressure.
High pressure is when the molecules in the atmosphere are more tightly packed
together. When the atmosphere presses in with less force we say that there is
a
low pressure
in the area. Low pressure is when the molecules in the atmosphere are more
loosely packed together.
When the atmosphere is heated it expands. The density of the gas molecules
lessons creating a
lower pressure.
Gases in the air move around trying to equalize the pressure. When
a low pressure area is next to a high pressure area, the gases will
move from the
high to low pressure
areas to try of equalize the pressure.
The moving about of these gases is wind.
Remember winds blow from
High
→
Low.
or from
Warm
→
Cool
Land Breezes
& Sea Breezes
Water, unlike air and land, does not change
temperature quickly. It can absorb a lot of heat energy before the temperature
of the water changes. The same is true in reverse. Water must lose a lot of
heat energy before it cools noticeably.
During the day the sun heats the land quickly. As the land heats, the air
above the land is heated. The hot air rises becoming less dense creating a
low pressure.
The air over the sea is cooler because it takes much longer to heat water.
The air over the sea keeps its
high pressure.
§The
differences in pressure creates wind or a breeze. Winds blow from the sea to
the land to try to equalize the pressure. This is called a sea breeze.
At
night the land cools rapidly. Because the air of the sea is warmer, the wind's
direction changes. The cooler heavier air over the land forms a
high pressure
causing the air to move towards the sea where the air
pressure is lower.
This is called a land breeze.
Source of Information
0507.8.1
Compare the climates of coastal and inland areas at similar latitudes to
demonstrate the ocean’s impact on weather and climate.
