Observations of chemical reactions are summarized in certain generalizations called the laws of chemical change.  The three laws of chemical change are;

1)  Law of Conservation of Mass

2)  Law of Constant Composition

3)  Law of Multiple Proportions

Law of Conservation of Mass

  • States that during a chemical reaction, matter is neither created or destroyed

Mass of reactants = mass of products

Law of Constant Composition

  • The percentage composition by mass in particular compounds never varies
  • In other words, in the formation of a compound, the mass of 1 element needed to combine with a given mass of another is always the same
  • E.g. 39.37% Na : 60.73% Cl for compound NaCl

Law of Multiple Proportions

  • Atoms of 2 elements can combine in more than 1 way

e.g.   elements H & O can form water (H2O) and hydrogen peroxide                               (H2O2)

—both have different physical and chemical properties despite containing the same atoms i.e. H2O2 bleaches most dyes while H2O does not

  • When the proportions (by mass) in which 2 elements combine to form 2 different compounds are divided by each other, the result is a fraction composed of small whole numbers

Or in other words…..

  • When 2 elements, A and B, form more than one compound, the mass of element A divided by the mass of element B in one compound, compared with mass of A divided by the mass of B in the second compound gives a ratio of small whole numbers
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Gene S.
Gene S.
6 years ago

I don’t understand the laws, can someone explain?

Jack S.
Jack S.
7 years ago

This is nice, it helped me

Rejean B.
Rejean B.
8 years ago

NICE WORK !!!

lenalee
lenalee
9 years ago

tnx a million it help a lot

Eghosa
Eghosa
10 years ago

Tnx a lot it helpd me n my assignment,u guys r doin a great job

Devil Oren
Devil Oren
10 years ago

This is so useful and more should make this web site for more learning for generations!

jonathan
jonathan
10 years ago

do you have the name of the discoverer of these 3 laws

Red
Red
10 years ago

Thanks! It helped me alot… coz its my assignement… 😀 haha xD

precious
precious
11 years ago

thanks for the help, it helped me a lot… 🙂 its my assignment. ^^

ley-J
ley-J
11 years ago

nice one,,it can help more people,,most especially to the chemists,,

Waahtari
Waahtari
12 years ago

Thanks!..
it really helped me.