1. Early Theories of Matter
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 = ,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