- Slides: 9
Section 4. 1 Early Theories of Matter
Four Components of Matter l l l Early Greek philosophers associated properties of matter with Water, Earth, Air, and Fire. They thought matter was infinitely divisible This incorrect belief lasted until the 1800 s.
Democritus l l l Greek philosopher (460 -370 B. C. ) First to propose matter was NOT infinitely divisible Atomos- indestructible particles
Democritus’s Ideas l l l Matter is composed of empty space Atoms are solid, homogeneous, invisible particles Different kinds of atoms have different shapes and sizes Differing properties of matter come from the different shapes and sizes of atoms. Changes in matter come from changes in grouping of atoms
Aristotle l l l Criticized Democritus’s ideas about atoms. Invisible particles do not exist - No Atoms! Accepted view for 2, 000 years
John Dalton l l 1766 -1844 School teacher from England Revived Democritus’s ideas about atoms Developed the modern atomic theory based on scientific research of the time.
Dalton’s Atomic Theory l l l All matter is composed of extremely small particles called atoms All atoms of an element are identical and specific to that element only. Atoms cannot be created, divided, or destroyed Different atoms combine in simple whole-number ratios to form compounds. In a chemical reaction, atoms are separated, combined, or rearranged.
Atom l Smallest particle of an element that retains the properties of that element World Population = 6, 000, 000 Atoms in a Penny= 29, 000, 000, 000
Homework l l l 1 -5 on page 91 Must write in COMPLETE sentences in order to get credit!!! Will be collected tomorrow