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14/15 Fall semester
Engineering Chemistry
Instructor: Rama Oktavian
Email: [email protected]
Office Hr.: M.13-15, Tu. 13-15, W. 13-15, Th. 13-15, F. 09-11
Outlines
1. Mass conservation theory of matter
2. Atom: Theory
3. Compounds: Bonding
4. Mixtures
Review
Unit conversion
Physical and chemical properties
Review
Significant figure in measurement
Mass conservation
Fundamental law
the total mass of substances does not change during a
chemical reaction - Antoine Lavoisier (1 743-1 794)
The number of substances may change, but the total amount
of matter remains constant.
matter cannot be created or destroyed.
Mass conservation
Fundamental law - the law of definite (or constant) composition
no matter what its source, a particular compound is
composed of the same elements in the same parts (fractions)
by mass
Denoted as mass fraction or mass percent, mass %
Mass conservation
Fundamental law - the law of definite (or constant) composition
Mass conservation
Example
Mass conservation
Multiple proportion
if elements A and B react to form two compounds, the different
masses of B that combine with a fixed mass of A can be
expressed as a ratio of small whole numbers.
Mass conservation
Conceptual question
Atom theory
Atomic Number , Mass Number , and Atomic Symbol
Isotopes of an element are atoms that
have different numbers of neutrons and
therefore different mass numbers.
Example: 12C, 13C, 14C
Compound: Bonding
Elements combine in two general ways:
1. Transferring electrons from the atoms of one element to
those of another to form ionic compounds
2. Sharing electrons between atoms of different elements to
form covalent compounds
Compound: Bonding
Ionic bonding
Compound: Bonding
Covalent bonding
Covalent compounds form when elements share electrons,
which usually occurs between nonmetals
Atoms of different elements share electrons to form the
molecules of a covalent compound
Compound: Bonding
Covalent bonding mechanism
Mixtures
Classification of mixtures
matter usually occurs as mixtures, such as air, seawater, soil,
and organisms
A heterogeneous mixture has one or more visible boundaries
between the components
Example: rocks
A homogeneous mixture has no visible boundaries because
the components are mixed as individual atoms, ions, and
molecules.
Example: sugar dissolves in water
Mixtures
Summary of matter