CHAPTER 1

INTRODUCTION TO CHEMISTRY?

Chemistry?

2

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

4

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

6

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

7

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.

9

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