Second lesson
Structure of matter
By end of the lesson, you will know about the following things
# What is atom and molecule?
# Atomic and molecular mass
# Gram atomic and gram molecular mass
# The short history of atomic theory
# Postulates and limitations of Dalton’s law
# laws of chemical combinations
# Diffusion
# Brownian movement
1.1Dalton Atomic Theory
All matters are made by mote, it is very ancient comment. Greek philosopher Democritus commented that all real matters are made by undivided mote. Democritus called these mote atomos. The word atomos has come from Latin word ‘a’ and ‘tomos’. ‘a’ means no and ‘tomos’ means divide. So atomos means what can’t be divided. But Aristotle commented that you can divide matters as you will and matters are incessant.
At last Dalton established the atomic theory in 1803. the pillar of classical chemistry is this atomic theory and Dalton is know to all as the founder of chemistry. Dalton was a school teacher.
1.2 Postulates of Dalton’s atomic theory
(1) Every matter are made by mote that name is atom. Simple matters mote’s name is simple atom and compound matters mote’s name is compound atom
(2) The attribute and mass of all atoms of one matter are same.
(3) The attribute and mass of various atoms of different matters are not same.
(4) If you affix two or more matters co-exist, it will creates new matter.
(5) Atoms participate in chemical reaction.
(6) By chemical reaction no atom can be destroyed or created.
(7) Atoms are indivisible; they have no creation or destroying.
1.3 Limitations of Dalton’s atomic theory
(1) In Dalton’s theory there have no difference between simple and compound atoms.
(2) In Dalton’s theory, atoms are invisible mote. But by modern researching, it has been seen that atoms are visible and atoms are structure by electron, proton and neutron
(3) In Dalton’s theory the attribute and mass of all atoms of one matter are same. But by modern researching, it has been that one matter have various mass atoms.
1.4 The difference of Atoms and molecules
Atoms | Molecules |
1. Atoms are the mote of simple matters | 1. Molecules are the mote of compound matters |
2. Atoms participate in chemical reaction | 2. molecules don’t participate in chemical reaction |
1.5 Atomic and molecular mass
Atoms and molecules are very dumps. Their masses are also very few. Now scientists determine their mass by mass spectrophotometric method in surely. The best portable hydrogen’s atom’s mass is 1.67 X 10-24g. The heavy uranium’s atom’s mass is 3.95 X 10-22g. Water’s a atom’s mass is 2.99 X 10-23g. So it is very hard to keep in mind these mass. And for this purpose scientist use relativity mass in view of these mass.
In 1803, Dalton received hydrogen’s atom’s mass as a standard atomic mass. At present the scientists have received the 1/12 allotment of carbon-12 isotope’s mass.
Simple matter atom’s mass
Simple matter’s atomic mass = .
The 1/12 allotment of carbon-12 isotope’s mass
Matter’s molecule mass
Molecular mass = .
The 1/12 allotment of carbon-12 isotope’s mass
1.6 laws of chemical combinations
There have five laws of chemical combinations. Such as-
(1) The law of conservation of mass
(2) The law of constant proportion
(3) The law of multiple proportion
(4) The law of reciprocal proportion
(5) The law of gaseous volume
1.7 The law of conservation of mass
This law is also known to all the law of indestructibility of matter. In 1774, french scientist Lavoy Sea discovered this law. You can explain this law in following.
(1) You can’t create or destroy matter but you can change matter from one static to other static only or
(2) In any chemical reaction the produced matter’s total mass are the same of total mass of element which have participate in chemical reaction.
1.8 The law of constant proportion
This law is also called the law of fixed ratio or fixed combinations. In 1799, french scientist Joseph Louis proust discovered this law. It is----
“By any source the same simple matters is appertained in a compound matter in a fixed ratio or proportion.”
1.9 The law of multiple proportions
In 1803, Dalton discovered this law. It is-----
“If two simple matters appertain to each other and they create two or more compound matter, the different mass of any matter of these compound matters appertain to a fixed proportion of other simple matter then the masses keep a simple ratio between them such as 1:2, 2:3, 3:4, 3:5 etc.”
1.10 The law of reciprocal proportion
In 1792, Richter discover this law .It is--------
“In which ratio of mass two or more simple matters appertain to a other simple matter’s mass separately; they obey the fixed ratio or sub ratio or simple ratio when they appertain to each other
1.11 The law of gaseous volume
In 1808, french Joseph Louis Gay-Lussac discovered this law. It is only for gas matter not for solid or liquid matters. The law is------
“When different gas react chemically, (1) there will have a simple proportion between their volumes and (2) if the production of Reaction are gas, there will also have a simple proportion between production and the elements of reaction.
THE END
