Characteristics of “Air” “Air” is a general term for the gases that make up our atmosphere – 78% Nitrogen – 21% Oxygen “Air” has volume – it takes up space – Gases expand to fill their containers – Gases are easy to compress “Air” has mass and weight

Air pressure – is the force exerted by the molecules that make up air – is the weight of air – decreases with altitude

#1 Water Wonder Low air pressure inside cup because there is little air High air pressure outside of cup, pushing up on the index card

#2 – Balloon Blowout

#3 – Bottle Business Hot water warms and expands the air Air cools and condenses, resulting in low pressure Air outside of the jug has higher pressure than the air inside the jug

#4 – Candle Craziness How is Candle Craziness similar to Bottle Business??? Video

#5 – Balloon Bonanza Low air pressure between balloons because the molecules don’t have time to touch the balloons’ surfaces as they rush by High air pressure on the sides of the balloons

#6 – Silly Straws One Straw – sucking lowers the air pressure inside your mouth and the high pressure outside pushes the liquid up the straw Two Straws – air coming up second straw keeps the air pressures in equilibrium

#7 – Paper Pandemonium The faster air moves, the more the air pressure decreases Blowing air under the paper lowers the air pressure under the paper so the paper is pushed down Blowing air over the paper lowers the air pressure over the paper so the paper is pushed up

#8 – Straw Sensation Adding air inside bottle increases the air pressure in the bottle The high pressure in the bottle pushes on water and forces it up the straw

Air Pressure High Pressure – occurs when air is compressed Low Pressure – occurs when air is expanded – occurs when air moves High and Low pressure areas are relative Air moves from areas of high pressure to areas of low pressure, in an effort to reach equilibrium Air movement results in a force applied to objects

#9 – “Egg”straordinary Egg Video

Wind Created by differences in air pressure The greater the difference, the faster the wind moves

What causes differences in air pressure?

Temperature Differences – Warm air rises because it is less dense than cooler air When air rises, air pressure is low – Cool air falls because it is more dense than warmer air When air falls, air pressure is high

Convection Currents Observed only in liquids and gases Warm substance rises and cool substance sinks

Air Pressure & Temperature Inversely Proportional – As air pressure falls, temperature rises… because less pressure means molecules can move around more, and movement leads to increased heat energy and higher temperatures – As air pressure rises, temperature falls… because greater pressure means molecules are compressed and moving less

What causes differences in temperature?

Unequal heating of the Earth – Amount of Sunlight – Cloud Cover – Atmospheric Gases – Large Bodies of Water Water takes longer to change temperature than land

Amount of Sunlight

Equator receives most direct sunlight Poles receive least direct sunlight

Cloud Cover

Atmospheric Gases

Various gases absorb different amounts of solar energy – Many gases that absorb solar energy leads to warmer temperatures – Few gases that absorb solar energy leads to cooler temperatures

Large Bodies of Water