SPI Atmospheric 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) Jupiter Earth 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 Atmospheric Composition Notes Science Earth's Atmosphere Earth’s atmosphere is a mixture of various gases Nitrogen 7 N 14.0 Oxygen 8 O 16.0 Argon 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 Atmospheric Composition Notes Science Nitrogen 7 N 14.0 Oxygen 8 O 16.0 Argon 18 Ar 39.9

Has Earth's atmosphere ever changed? Notes SPI 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 Science SPI Physical or Chemical Changes

Physical Change: It looks different, but is still the same material. Liquid Water Solid Water Water Vapor H2OH2O H2OH2OH2OH2O Notes Science SPI Physical or Chemical Changes Example: Changes of state/phase ARE NOT chem reactions In other words, liquid to solid to gas are only physical changes No chemical reaction has occurred.

Examples of Physical Change  Melting  Freezing  Boiling  Cutting  Crushing  Tearing  Breaking  Smashing  Dissolving Notes Science SPI Physical or Chemical Changes In every example here, the appearance is changed, but the composition remains the same.

Chemical Changes  Occur 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 elements  Atomic bonds break apart and new atomic bonds are formed  Valence 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 connected  Chemical bonding occurs during a chemical reaction resulting in a chemical change Notes Science SPI 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 Science SPI 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 Trick Chemical reactions can H.O.P.E. and 4FPC 4FPC F: 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.)