ee laws are thought to have originated with Aristotle, who believed that the laws are necessary conditions for rational thinking to occur

1. Antoine Lavoisier’s Law of
Conservation of Mass
Joseph Proust’s Law of Definite
Proportions
John Dalton’s Law of Multiple
Proportions

2. ANTOINE LAVOISER
• French chemist is usually considered the
founder of modern chemistry. Among his
many achievements he advanced the use of
quantitative chemical methods, was largely
responsible for developing the modern
conception of a chemical element, and
revealed the true nature of combustion.

3. Lavoiser’s discoveries marked a turning point in
chemistry.
1.The total mass remained the same during a
chemical reaction , showing that matter was
conserved.
2.Each substance required a specific mount of
oxygen , illustrating the law of definite proportions
3.The amount (mass) of product was different for
each set of reactants ; and
4. Excess reactants ( oxygen in this case) remained
unreacted when the reaction was completed.

4. • LAW OF CONSERVATION OF MASS
STATES THAT MATTER IS NEITHER CREATED
NOR DESTROYED IN A CHEMICAL
REACTION

5. JOSEPH PROUST
French chemist , born in angers and educated in
Paris. He is best known for establishing the
chemical law of definite proportions sometime’s
called Proust’s law, which states that the elements
in a compound are all present in a fixed proportion
by weight , regardless of how the compound is
prepared. Proust included this law in a paper that
published in 1794. However, his law was not widely
accepted until Jons Jacob Berzeluis, a swedish
chemist gave proust credit for the law in 1911.
Proust also discovered grape sugar, or what is now
called glucose. In 1816, he was elected to the
French Academy of Sciences.

6. • Water 11.19
• Hydrogen 88.81
• 88.91/11.19= 7.94
• 11.19/11.19=1.00
• O:H mass ratio is 7.94:1.00 or 8:1
• The law of definite proportions tells us that
water always contains hydrogen and oxygen in
the same proportions 2:1 in number of atoms,
about 8:1 by weight or mass

7. JOHN DALTON
A british schoolmaster and chemist , was fascinated
by the patchwork puzzle of the elements.
He made studies of the way in which the various
elements combined with one another to form
chemical compound. Dalton is regarded as one of
the most significant figures in atomic theory
because he made the subject quantitatve.vHe
showed how these atoms link togetehr in definite
proportions …molecules.