SPI 0807.9.5Atmospheric Composition Notes Science

An atmosphere is the mass of gases that surrounds a planet and is held in place by the gravity of the planet.Planetary atmospheres are common in our solar system(Even the Moon has a thin atmosphere)

JupiterEarth

The Moon

What is an Atmosphere?

Mars Saturn

Earth's Current Atmosphere…(approx) 78% nitrogen…(approx) 21% oxygen…(approx) 1% other gases (argon, water vapor, carbon dioxide, ozone, etc)

SPI 0807.9.5Atmospheric Composition Notes Science

Earth's Atmosphere

Earth’s atmosphere is a mixture of various gases

Nitrogen

7

N

14.0Oxygen

8

O

16.0Argon

18

Ar

39.9

Remember! Our atmosphere is a MIXTURE & not a compound

Earth's Current Atmosphere…(approx) 78% nitrogen…(approx) 21% oxygen…(approx) 1% other gases (argon, water vapor, carbon dioxide, ozone, etc)

SPI 0807.9.5Atmospheric Composition Notes Science

Nitrogen

7

N

14.0Oxygen

8

O

16.0Argon

18

Ar

39.9

Has Earth's atmosphere ever changed?

NotesSPI 0807.9.5

Atmospheric Composition Science

Earth’s first atmosphere was mostly carbon dioxide, water vapor, & ammonia

Yes it has!

What changed it? Plants converted the carbon dioxide to oxygen , and this oxygen broke down the ammonia into nitrogen.

Physical Changes A change of matter from one form to another without a change in chemical properties.

Changes the appearance of an object, but does not change the composition of the object.

In other words, the way it looks is changed, but what it is does not change. (kind of like dressing up for a costume party)

Physical changes do not form new substances.

Can be fairly easily undone or reversed

Notes ScienceSPI 0807.9.8

Physical or Chemical Changes

Physical Change: It looks different, but is still the same material.

Liquid Water Solid Water Water Vapor

H2O H2O H2O

Notes ScienceSPI 0807.9.8

Physical or Chemical Changes

Example: Changes of state/phase ARE NOT chem reactionsIn other words, liquid to solid to gas are only physical changes

No chemical reaction has occurred.

Examples of Physical Change

MeltingFreezingBoilingCuttingCrushingTearingBreakingSmashingDissolving

Notes ScienceSPI 0807.9.8

Physical or Chemical Changes

In every example here, the appearance is changed, but the composition remains the same.

Chemical ChangesOccur when 2 or more substances, due to a chemical reaction, form a compound & change into a new substance.

Compounds are formed when you combine 2 or more or more different reactive elementsAtomic bonds break apart and new atomic bonds are formedValence Electrons are transferred or shared(F.Y.I. This is called ionic & covalent bonding)

….so in other words chemical changes, chemical bonding and chemical reactions are all connectedChemical bonding occurs during a chemical reaction resulting in a chemical change

Notes ScienceSPI 0807.9.8

Physical or Chemical Changes

5 Key Points About All Chemical Reactions:

1) A new substance is created

2) The properties of the new substance are different from the substances that you started with

3) No atoms are created or destroyed during chemical reactions

4) Atomic bonds are broken and new bonds are formed (at the valence electron level)

5) compounds come from chemical reactions

Notes ScienceSPI 0807.9.8

Physical or Chemical Changes

H.O.P.E.H: Heat-Heat may be given off (it may get hot)O: Odor-There may be a change in odor (how it smells)P: Pop-It may pop or bang (make a loud noise)E: Explode-It may explode (like fire crackers or dynamite)

Chemical Changes-Memory TrickChemical reactions can H.O.P.E. and 4FPC

4FPCF: Foam-It may foam (like vinegar & baking soda) F: Flash-It may flash (like a grenade or gun powder)F: Fizzle-It may fizzle (make a hissing sound like Alka-Seltzer)F: Flame- It may burn (like burning paper or wood)P: Precipitate-It may form a solid substance (called a precipitate) C: Color- It may change color (red to blue, green to orange, etc.)