democrituss idea of the atom

just a guess

Democritus idea of the atom has been called the best guess in antiquity. Thats because it was correct in many ways, yet it was based on pure speculation. It really was just a guess. Heres what Democritus thought about the atom: How many times could you cut this piece of cheese in half? How small would the smallest pieces be? All matter consists of atoms, which cannot be further subdivided into smaller particles. Atoms are extremely smalltoo small to see. Atoms are solid particles that are indestructible. Atoms are separated from one another by emptiness, or void. Q: How are Democrituss ideas about atoms similar to modern ideas about atoms? A: Modern ideas agree that all matter is made up of extremely small building blocks called atoms. Q: How are Democrituss ideas different from modern ideas? A: Although atoms are extremely small, it is now possible to see them with very powerful microscopes. Atoms also arent the solid, uncuttable particles Democritus thought. Instead, they consist of several kinds of smaller, simpler particles as well as a lot of empty space. In addition, atoms arent really indestructible because they can be changed to other forms of matter or energy.

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keep on moving

Did you ever notice dust motes moving in still air where a beam of sunlight passes through it? You can see an example in the forest scene in the Figure 1.2. This sort of observation gave Democritus the idea that atoms are in constant, random motion. If this were true, Democritus thought, then atoms must always be bumping into each other. When they do, he surmised, they either bounce apart or stick together to form clumps of atoms. Eventually, the clumps could grow big enough to be visible matter. Q: Which modern theory of matter is similar to Democritus ideas about the motion of atoms? A: The modern kinetic theory of matter is remarkably similar to Democritus ideas about the motion of atoms. According to this theory, atoms of matter are in constant random motion. This motion is greater in gases than in liquids, and it is greater in liquids than in solids. But even in solids, atoms are constantly vibrating in place.

cutting the cheese

Democritus lived in Greece from about 460 to 370 B.C.E. Like many other ancient Greek philosophers, he spent a lot of time wondering about the natural world. Democritus wondered, for example, what would happen if you cut a chunk of mattersuch as a piece of cheese into smaller and smaller pieces. He thought that a point would be reached at which the cheese could not be cut into still smaller pieces. He called these pieces atomos, which means uncuttable in Greek. This is where the modern term atom comes from.

why matter varies

Democritus thought that different kinds of matter vary because of the size, shape, and arrangement of their atoms. For example, he suggested that sweet substances are made of smooth atoms and bitter substances are made of sharp atoms. He speculated that atoms of liquids are slippery, which allows them to slide over each other and liquids to flow. Atoms of solids, in contrast, stick together, so they cannot move apart. Differences in the weight of matter, he argued, could be explained by the closeness of atoms. Atoms of lighter matter, he thought, were more spread out and separated by more empty space. Q: Democritus thought that different kinds of atoms make up different types of matter. How is this similar to modern ideas about atoms? A: The modern view is that atoms of different elements differ in their numbers of protons and electrons and this gives them different physical and chemical properties. Dust motes dance in a beam of sunlight.

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thats ridiculous

Democritus was an important philosopher, but he was less influential than another Greek philosopher named Aristo- tle, who lived about 100 years after Democritus. Aristotle rejected Democritus idea of the atom. In fact, Aristotle thought the idea was ridiculous. Unfortunately, Aristotles opinion was accepted for more than 2000 years, and Democritus idea was more or less forgotten. However, the idea of the atom was revived around 1800 by the English scientist John Dalton. Dalton developed an entire theory about the atom, much of which is still accepted today. He based his theory on experimental evidence, not on lucky guesses.

instructional diagrams

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questions

according to democritus, atoms are

a) too small to see.

b) indestructible.

c) unable to be subdivided.

-->  d) all of the above

democritus thought that atoms are motionless.

a. true

-->  b. false

democritus thought that atoms are separated from each other by empty space.

-->  a. true

b. false

what happened to democritus ideas about atoms?

a) they were ridiculed by aristotle.

b) they were widely accepted in his own lifetime.

c) they were almost forgotten for more than 2000 years.

-->  d) two of the above

democritus ideas were based on experimental evidence.

a. true

-->  b. false

diagram questions

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