Download - Chapter 1 Introduction2
CHAPTER 1
INTRODUCTION TO CHEMISTRY?
Chemistry?
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Chemistry in ancient ages
• Basic daily activities of ancient people:– Cooking– Baking pottery– Smelting ores– Brewing wine and beer
• These activities requires understanding of basic chemistry
• Application of knowledge for practical purposes - technology
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Theory vs. behaviour of matter• Knowledge is obtained based on observation -
behaviour of matter
• Aristotle is the first to formulate rational theories of chemistry
• Theories are not tested by experimentation
• Dominated western thinking for 2000 years
5Aristotle (384-322
BC)
Alchemy• Mystical mixture of chemistry and magic in
Middle Ages – 500 to 1500 CE• Searched for:
– A “philosopher’s stone” that would turn cheaper metals into gold
– An elixir for immortality
• Discovered:– Techniques – extraction and distillation– New chemical substances
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Modern Alchemy
• Emergence of experimental method as a basis of modern chemistry
• Number of innovations:– Lye and laundry bleach from salt– Transistors and computer chips from sand– Plastics, fibers, pesticides, drugs and detergents
from crude oil
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Chemistry in modern world• The Baconian Dream (Francais Bacon, 1561-
1626): – Science should be experimental– Science could solve the world’s problem and enrich
human life with new inventions – increasing happiness and prosperity
• In 20th century, human life has been improved by science and technology– Use of pesticides, fertilizers: increased food supply– New materials: clothing, shelter, transportations
and communications8
What is chemistry?
• It is the study of matter and the changes it undergoes
• Matter is anything that occupies space and mass
• A central science: basics knowledge of biology, physics, geology etc.
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CLASSIFICATION OF MATTER
ELEMENTS
• Elemental substances contain only one type of atom
• Elements are the building blocks of matter• There are 115 known elements today, 90
which occur naturally• The periodic table displays the elements
ELEMENTS (Cont)
• Each element has a unique symbol– The first letter is always capitalized, the second
letter is always lower case• Fluorine is F, not f• Cobalt is Co, not CO (which is carbon monoxide)
• The smallest unit of an element is the atom
COMPOUNDS
• Pure substances containing more than one different element.– NaCl (table salt)
• Contains sodium (Na) and chlorine (Cl)• NaCl is the chemical formula
– H2O (water)• Contains 2 atoms of hydrogen (H) and 1 atom of oxygen (O)• H2O is the chemical formula
• Elements in compounds are combined in a definite ratio– H2O is water but H2O2 is hydrogen peroxide
COMPOUNDS (cont)
Are H2 and CO2 considered elements or compounds? Why?
MIXTURE
Homogeneous : components are uniformly mixed.
Eg : a glass of sweetened lemonade
Heterogeneous : components are not uniformly mixed
Eg : A scoop of chocolate chip ice cream
Mixture are combinations of 2 or more pure substance
STATES OF MATTER
Solid Liquid Gas
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
CHANGES IN STATE
• Melting: Solid to liquid• Boiling: Liquid to gas• Sublimation: Solid to gas
– The above three require input of energy
• Condensation: Gas to liquid• Freezing: Liquid to solid• Deposition: Gas to solid
– The above three release energy
PHYSICAL CHANGES
• There is no change in composition– Examples include:
• Any change in the state of matter (e.g. freezing or boiling water)
• Sawing wood• Crushing a tablet• Bending a wire• Dissolving salt in water
WATER AND ITS STATES OF MATTER
What is composition of ice, water and steam?
CHEMICAL CHANGES
• There is a change in composition.– Also called chemical reactions
• Examples:– Tarnishing of silver (Ag forms AgS) – Rusting of iron (Fe forms Fe2O3)
CHEMICAL REACTIONS• Are expressed using chemical equations.
• Rusting of iron:4 Fe + 3 O2 2 Fe2O3 (rust)
reactants products
Meaning: Four atoms of iron react with three
molecules of oxygen to form two molecules of rust