Physical science module 3

1. The Emergence of Ideas
About the Atom
MODULE 3

2. LEARNING OBJECTIVES:
• Describe the ideas of the ancient Greeks on
the atoms and the elements;
• Describe the contributions of alchemists to
chemistry;
• Discuss the ideas of alchemy and its
significance to ideas formulated on the
atom; and
• Point out the main ideas in the discovery of
the structure of the atom and its subatomic
particles.

5. Ancient Greeks’ Concept of the Atoms and the
Elements
Element is a pure substance that
is made up of only one kind of
atom.
Atom is the basic unit of matter.
5th century BCE= theory of an atom
started.

6. Leucippus
(480 BCE-460 BCE)
He believed that all things
are made up of tiny,
indivisible particles.
Mentor of Democritus

7. Democritus of Abdera
(460 BCE-370 BCE)
“All matter was composed of small,
indestructible particles, which he
called atoms.”
Democritus and Leucippus supporter of
their ideas are called atomists.
Student of Leucippus

8. Leucippus and Democritus’ theory that atoms were
indivisible was strongly opposed by Aristotle.
ARISTOTLE

9. ARISTOTLE (384 BCE-322 BCE)
“There was no smallest part of
matter.”
All matter consisted of four
elements- earth, fire, water and
air.

10. Alchemists’ Contribution to Modern
Chemistry
•Alchemy is a medieval practice which aims to
transform common metal into gold.
•It also aims to create the elixir of immortality
which is a portion that grants the drinker eternal
life.
•Alchemists contributed to modern chemistry
with their invention of chemical methods such as
distillation, percolation, and extraction.

11. DALTON’S ATOMIC THEORY
John Dalton
(1766-1844)
1. Matter is composed of small
indivisible particles called atoms.
2. Atoms of the same element are
identical.
3. Compounds contain atoms of more
than one element.
4. In a compound, atoms of different
elements always combine in the
same proportion by mass.

12. Law of Definite
Proportion
Law of Multiple
Proportion
Law of
conservation of
Mass
A given chemical
compound always
contains its
components in fixed
ratio.

13. Law of Definite Proportion
Joseph Proust
French chemist
• Experiments conducted between 1798 and 1804
on the elemental composition of water and
copper carbonate by Proust.
• It stated that chemical compounds are formed of
constant and defined ratios of elements, as
determined by mass. For example, carbon dioxide
is composed of one carbon atom and two oxygen
atoms.

15. Law of Definite Proportion
Example: A pure sample of Carbon dioxide (CO2) contains 30 g of
Carbon. How many grams of Oxygen are present in this sample?
CO2 12gC, 32g O
C= 12
O=16x2=32
Given: 30g of C, ?g of Oxygen
30gC x 32g O=
1 12gC
80g O

16. Law of Definite Proportion
CO2
12gC = 32g O
30gC=?O
30gC = __x__
12gC 32gO
12x = 30(32)
12x = 960
12x = 960
12 = 12
x = 80gO

17. Law of Multiple Proportion
Different compounds may contain the same
element but still differ in terms of the number of
atoms in its composition.
When two elements form a series of compounds
the ratio of the masses of the 2nd element that
combine with 1 gram of the first element can
always be reduced to small whole numbers.
CO
12gC= 16gO
12gC= 16gO
12 12
1gC= 1.33gO
CO2
12gC= 32gO
12gC= 32gO
12 12
1gC= 2.666gO

18. Law of Conservation of Mass
The matter cannot be created nor destroyed.
“The number of atoms remains constant
throughout the reaction. Since the number of
atoms doesn’t change, the mass must remain
constant as well.”
Reactants Products
C= 8(2) =16
H= 18(2) = 36
O= 2(25) = 50
C= 1(16) =16
H= 2(18) = 36
O= 2(16) + 1(18)= 50

19. Cathode Ray Tube (CRT)

20. Activities for this module
What Have I Learned So Far?
1. Cite similarities and differences between the ancient
Greek's concept of an atom and Dalton’s atomic theory?
2. How did alchemy contribute to the formation of the
atomic theory?
Solve the Definite Proportion of the following: (with
Solution)
1. A pure sample of Sodium Fluoride (NaF) contains 35g of
Sodium. How many grams of Fluorine are present in this
sample?
2. If there are 42g of Hydrogen in a sample of pure Methane
(CH4). How many grams of Carbon are present?
3. If there are 19g of Oxygen in a sample of Aluminum Oxide
(Al2O3), How many grams of Aluminum are present?

21. Safe Lab Practices
List three safe lab practices in the boxes provided.
1st safe lab practice
2nd safe lab practice
3rd safe lab practice

22. Safe Lab Practices 2
4th safe lab practice
5th safe lab practice
6th safe lab practice

23. In the Event of a Lab
Accident…
• (Use this space to discuss procedures to follow in the
event of a lab accident.)

24. At the End of Your Lab Time…
• (Use this space to discuss what should be done at the end
of your lab time.)

25. Remember…
Safety First!
(Enter your own creative tag line above)