1. Section 4.1 Early Theories of Matter

2. Four Components of Matter • 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 1800s.

3. Democritus • Greek philosopher (460-370 B.C.) • First to propose matter was NOT infinitely divisible • Atomos- indestructible particles

4. Democritus’s Ideas • 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

5. Aristotle • Criticized Democritus’s ideas about atoms. • Invisible particles do not exist- No Atoms! • Accepted view for 2,000 years

6. John Dalton • 1766-1844 • School teacher from England • Revived Democritus’s ideas about atoms • Developed the modern atomic theory based on scientific research of the time.

7. Dalton’s Atomic Theory • 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.

8. Atom • Smallest particle of an element that retains the properties of that element World Population = 6,000,000,000 Atoms in a Penny= 29,000,000,000,000,000,000,000

9. Homework • 1-5 on page 91 • Must write in COMPLETE sentences in order to get credit!!! • Will be collected tomorrow