Evidence for the Existence of Atoms Discussion and Interpretations

Station 1: Water Droplet Observations –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 see  maybe 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.