Evidence for the Existence of Atoms

Discussion and Interpretations

Station 1: Water Droplet Observatio

ns– did not

separate easily

– it spreads– drops

became different sizes

Interpretations– Atoms in a liquid do

not separate easily– Atoms in a liquid are

attracted to each other

– Atoms can be see thru– A substance can be

broken down until the particles are too small to seemaybe atoms are particles that cannot be further broken down

Station 2: Cutting a solid Observations

– At first difficult to break

– Different shapes & sizes

– Little crumbs– Still white– Color– Small particles

of same “stuff”– Jagged edges

Interpretations– Atoms can have

color– Atoms in solid

are compact– Atoms in solid

not as attracted to each other as they are in liquid

– Color stays same

– Atoms of solid take different shapes & sizes

Station 3: Mixing a Dark and Clear Liquid

Observations– Drop made a

circle that expanded

– Blue dye looked denser (not heavier)

– Went from a glob to spreading out

– Eventually mixed with each other

Interpretations– Atoms in a liquid move

around– Atoms have density– Atoms in same state

can mix– Drops of blue liquid

break into smaller drops & mix w/ water

– 2 types of atoms mixed– Maybe atoms in liquid

separate from each other, even though mixed

Station 4: Smelling an Aromatic Substance

Observations– Strong

smell– Could

smell from ~ 10 cm

– Nostrils burned

Interpretations– Atoms can smell– Atoms in gases have

density– Atoms can be in

different states– Atoms in gaseous state

can move– Atoms spread/travel on

their own– If liquids are made of

atoms, then small amounts of liquid atoms must move into the air

Station 5: Mixing 2 Clear Unknown Liquids

Observations– Both clear

liquids– Formed a

white solid (precipitate)

– 2 liquids can form a solid (new state of matter!)

Interpretations– Atoms can

combine to make something new!

– Some atoms don’t mix

– Atoms of different substances cause reactions

Station 6: Combining Acid & Chalk

Observations– Acid & chalk

fizzed– Chalk dissolved– Neither chalk or

acid bubbled before they were mixed

– Gas came out of chalk (fizzing)

Interpretations– Atoms in solid &

liquid can react to make a gas

– Atoms of different substances cause reactions

– Some atoms don’t mix

– Atoms combine to make new substance

Station 7: Block of Wood Observations

– Brown and rectangular

– Light & dark rings formed

– Wood grains appear to have a pattern

– Some parts smooth

– Some parts rough texture

Interpretations– Atoms line up– Atoms can

form intricate patterns

– Atoms can have structure

– Atoms can be dense & compact

Remember… Atoms are too small to be seen Use a model to explain how an atom

works, what it looks like b/c it’s too small to be seen

We use the atomic model to explain what matter is like

We observe indirect evidence for atoms b/c we cannot see them.

There is NO direct evidence for atoms b/c they are too small to be observed.

We use indirect evidence so we can talk about what how atoms might behave.