1- models of matter copy - wordpress.com empedocles aristotle was the most respected philosopher at...
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What is a model?
A model is a simplified description of a complex thing.
F-16 Fighter
Model of a F-16 Fighter
But a model is not the real thing!
Size relative to the real thing.
Matter is anything that has mass and occupies space. Around 450 BCE, a Greek scholar named Empedocles proposed a model for matter. He thought that all matter was composed of four “elements”:
What is Matter?
For example, wood might be 2 parts earth, 2 part fire, and 1 part water. Volcanic rock might be 1 part
earth and 3 parts fire.
Matter is anything that has mass and occupies space. Around 450 BCE, a Greek scholar named Empedocles proposed a model for matter. He thought that all matter was composed of four ”elements”:
Models of Matter
earth air fire water
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For example, wood might be 2 parts earth, 2 part fire, and 1 part water. While volcanic rock might be
3 parts fire and 1 part earth.
http://www.oldgrowthagain.com/firewood2cordsm.jpg http://iceblog.puddingbowl.org/archives/120-2081_IMG-thumb.JPGEmpedocles
For example, wood might be 2 parts earth, 2 part fire, and 1 part water. Volcanic rock might be 1 part
earth and 3 parts fire.
Matter is anything that has mass and occupies space. Around 450 BCE, a Greek scholar named Empedocles proposed a model for matter. He thought that all matter was composed of four ”elements”:
earth air fire water
Matter is anything that has mass and occupies space. Around 450 BCE, a Greek scholar named Empedocles proposed a model for matter. He thought that all matter was composed of four “elements”:
http
://w
ww
.cwu.
edu/
~war
ren/
Uni
t1/E
mpe
docl
es.jp
g
For example, wood might be 2 parts earth, 2 part fire, and 1 part water. While volcanic rock might be
3 parts fire and 1 part earth.
http://www.oldgrowthagain.com/firewood2cordsm.jpg http://iceblog.puddingbowl.org/archives/120-2081_IMG-thumb.JPGEmpedocles
Models of Matter
Aristotle was the most respected philosopher at about this time. He
preferred the model of Empedocles.For nearly 2000 years ,the “four elements” model was accepted.
Aristotle was the most respected philosopher at about this time. He
preferred the model of Empedocles.For the next 2000 years, the “four
elements” model was accepted.
Aristotle was the most respected philosopher at about this time. He
preferred the model of Empedocles.For the next 2000 years, the “four
elements” model was accepted.
About 50 years later, Democritus suggested a different model for matter. He thought that matter was made up of tiny, indivisible particles that he called atomos.
Democritus
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EmpedoclesAristotle
About 50 years later, Democritus suggested a different model for matter. He thought that matter was made up of tiny, indivisible particles that he called atomos.
Models of Matter
http
://w
ww
.cwu.
edu/
~war
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Empedocles
Aristotle was the most respected philosopher at about this time. He
preferred the model of Empedocles.For nearly 2000 years ,the “four elements” model was accepted.
Aristotle was the most respected philosopher at about this time. He
preferred the model of Empedocles.For the next 2000 years, the “four
elements” model was accepted.
Aristotle was the most respected philosopher at about this time. He
preferred the model of Empedocles.For the next 2000 years, the “four
elements” model was accepted.
About 50 years later, Democritus suggested a different model for matter. He thought that matter was made up of tiny, indivisible particles that he called atomos.
Aristotle
About 50 years later, Democritus suggested a different model for matter. He thought that matter was made up of tiny, indivisible particles that he called atomos.
Models of Matter
In 1650, Robert Boyle rejected the “four elements” model. He redefined the term element to mean, any pure substance that cannot be chemically broken down into simpler substances. By the 1800’s, scientists had discovered many of these elements.
In 1650, Robert Boyle rejected the “four elements” model. He redefined the term element to mean, any pure substance that cannot be chemically broken down into simpler substances. By the 1800’s, scientists had discovered many of these elements.
In 1650, Robert Boyle rejected the “four elements” model. He redefined the term element to mean, any pure substance that cannot be chemically broken down into simpler substances. By the 1800’s, scientists had discovered many of these elements.
Models of Matter
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BoylePriestlyOXYGEN
CavendishHYDROGEN
DavyPOTASSIUM
MAGNESIUM
CALCIUM
SODIUM
BARIUM
BORON
All matter is made of atoms.
Each element has its own kind of atom.
Compounds are created when atoms of different elements combine.
Atoms cannot be created or destroyed in chemical reactions.
In 1808, John Dalton proposed the atomic model for matter. The model states that:
Models of Matter
Dalton
In 1808, John Dalton proposed the atomic model for matter. The model states that:
To make a better model of the atom, scientists performed experiments. J.J. Thomson discovered that the atom contains very light, negatively charged particles (electrons). In Thomson’s “raisin bun” model, the atom is a positively charged sphere with embedded electrons.
To make a better model of the atom, scientists performed experiments. J.J. Thomson discovered that the atom contains very light, negatively charged particles (electrons). In Thomson’s “raisin bun” model, the atom is a positively charged sphere with embedded electrons.
To make a better model of the atom, scientists performed experiments. J J.J. Thomson discovered that the atom contains very light, negatively charged particles (electrons). In Thomson’s “raisin bun” model, the atom is a positively charged sphere with embedded electrons.
Models of Matter
Thomson cathode ray tube
A positive charge attracts the beamTherefore, the beam must be negatively charged.
A beam of particles can be made in this tube.
Raisin Bun model
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Raisin Bun model
Thomson
positive sphere
negative electron
To make a better model of the atom, scientists performed experiments. J.J. Thomson discovered that the atom contains very light, negatively charged particles (electrons). In Thomson’s “raisin bun” model, the atom is a positively charged sphere with embedded electrons.
To be continued ...
In 1909, Ernest Rutherford devised an experiment to test Thomson’s “raisin bun” model. Rutherford knew that some elements released high-speed, positively charged particles, that he called alpha(α)particles.
Models of Matter
In 1909, Ernest Rutherford devised an experiment to test Thomson’s “raisin bun” model. Rutherford knew that some elements released high-speed, positively charged particles, that he called alpha(α)particles.
Rutherford
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positive sphere
negative electron
Models of MatterRutherford predicted that if α-particles were directed towards a very thin piece of gold foil, they would go straight through the atoms of gold.
α-pa
rtic
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gold atom
The electrons might deflect the α-particle a bit, but the electrons do not have enough mass to have
much effect on the path of the α-particle.
Rutherford used polonium as a source of α-particles, a piece of gold foil and a detection screen that was coated with zinc sulfide, which produces a flash of light when the α-particle hits it.
Rutherford used polonium as a source of α-particles, a piece of gold foil and a detection screen that was coated with zinc sulfide, which produces a flash of light when the α-particle hits it.
Rutherford used polonium as a source of α-particles, a piece of gold foil and a detection screen that was coated with zinc sulfide, which produces a flash of light when the α-particle hits it.
Rutherford used polonium as a source of α-particles, a piece of gold foil and a detection screen that was coated with zinc sulfide, which produces a flash of light when an α-particle hits it.
lead box
α-particlespolonium
Models of Matter
zinc sulfide screen
flashesof light
gold foil
These are the expected results.
Gold Foil Experiment
These are the actual results.
Gold Foil Experiment
lead box
α-particlespolonium
zinc sulfide screen
flashesof light
gold foil
These are the actual results.
These results do not support the “raisin bun” model. There must be a small, dense, positively charged part of the atom. Rutherford realized that he had to change the model.
These results do not support the “raisin bun” model. There must be a small, dense, positively charged part of the atom. Rutherford realized that the model had to change.
These results do not support the “raisin bun” model. There must be a small, dense, positively charged part of the atom. Rutherford realized that he had to change the model.
Gold Foil Experiment
expected results for “raisin bun” model actual results
These results do not support the “raisin bun” model. There must be a small, dense, positively charged part of the atom. Rutherford realized that the model had to change.
Gold Foil ExperimentRutherford’s Nuclear Model
In Rutherford’s nuclear model, the atom is made of mostly empty space, with all of the positive charge and mass concentrated into a tiny nucleus. The position of the electrons are the same as Thomson’s model.
In Rutherford’s nuclear model, the atom is made of mostly empty space, with all of the positive charge and mass concentrated into a tiny nucleus. The position of the electrons are the same as Thomson’s model.
In Rutherford’s nuclear model, the atom is made of mostly empty space, with all of the positive charge and mass concentrated into a tiny nucleus. The position of the electrons are the same as Thomson’s model.
empty space
nucleus
electrons
Nuclear model
Bohr-Rutherford Model
Bohr-Rutherford model
Niels Bohr improved Rutherford’s model by showing that electrons travel around the nucleus in circular paths called orbits.
The evidence for this comes from emission spectra. These are a kind of light “fingerprint” that can be used to
identify elements.
Bohr
Rutherford’s Nuclear Model