Chapter 1.3 Flashcards
Whats the difference between a theory and law
Theory can be supported by evidence but can be difficult to prove. it attempts to explain phenomena and can often change with new evidence.
Law can be supported by multiple experiments and describes rather than explains natural phenomena.
atoms are:
mostly empty space and that most of the mass is in the nucleus.
What did Empedocles think? what was his evidence?
Empedocles suggested that all matter is made of four “elements”.
He didn’t have any evidence it was all conjecture!
what did Democritus think? What was his evidence?
Democritus believed that if you cut a material into tiny pieces you would eventually reach a piece that could not be further divided. He called this ‘atomos’, meaning ‘indivisible’. Democritus was forgotten for 2000 + years!
This was all conjecture! But Democritus was on the right track!
What was Dalton’s evidence?
evidence:
Used careful experiments to rank the elements based on their masses. Noticed that element masses were related to the mass of new chemicals formed from combinations of these elements.
what did thomson think? what was his evidence?
Evidence:
Using a cathode ray, he observed bits of atoms being deflected by a negatively charged plate and attracted by a positively charged plate!
what did rutherford think?
A piece of gold foil was hit with alpha particles, which have a positive charge. Most alpha particles went right through. This showed that the gold atoms were mostly empty space.
What was Bohr evidence?
evidence:
When heated, elements emit light of very specific wavelengths, and therefore very specific colours. This is like a light ‘fingerprint’!
how did Rutherford’s experiments improve technology?
Rutherford’s experiment showed the existence of a nuclear atom - a small, positively-charged nucleus surrounded by empty space and then a layer of electrons to form the outside of the atom.
what did Aristotle think?
He thought Empedocles’ idea wa correct so Democritus was forgotten for 2000 + years!
what was daltons inferences?
inferences:
- Dalton revived Democritus’ idea. He defined the atom as the smallest particle of an element.
- He described atoms as small, hard, indivisible spheres that are uniform throughout.
- Atoms of an element are all identical (particularly their mass)
- Atoms of different elements are different from each other.
what was thomson’s inferences?
inferences:
- Atoms are NOT just uniform spheres. They contain small particles with a negative electric charge called electrons.
- These electrons are spread throughout a positive sphere like raisins in a bun.
what was bohr’s inferences?
inferences:
- Electrons are restricted to specific regions of space called orbitals. (or ‘electron shells’)
- Since electrons in the same orbital have a similar energy, orbitals can also be called energy levels.
what was rutherford’s observation #1?
When small positively charged ‘alpha’ particles are fired at a thin sheet of gold, most of those particles will pass through unhindered.
Inference: Atoms are mostly empty space.
what was rutherfords observation #2?
Some alpha particles are deflected slightly as they pass through the foil.
Inference: The centre of an atom contains protons which repel the positively charged alpha particles.
