Page 34 - Physical chemistry understanding our chemical world

1

Introduction to physical

chemistry

Introduction

In this, our introductory chapter, we start by looking at the terminology of phys-
ical chemistry. Having decided what physical chemistry actually is, we discuss the
nature of variables and relationships. This discussion introduces the way relationships
underlying physical chemistry are formulated.
We also introduce the fundamental (base) units of the Syst`eme Internationale (SI),
and discuss the way these units are employed in practice.
We look at the simple gas laws to explore the behaviour of systems with no inter-
actions, to understand the way macroscopic variables relate to microscopic, molecular
properties. Finally, we introduce the statistical nature underlying much of the physical
chemistry in this book when we look at the Maxwell–Boltzmann relationship.

1.1 What is physical chemistry: variables,
relationships and laws

Why do we warm ourselves by a radiator?

Cause and effect

We turn on the radiator if we feel cold and warm ourselves in front of it. We become
warm because heat travels from the radiator to us, and we absorb its heat energy,
causing our own energy content to rise. At root, this explains why we feel more
comfortable.
While this example is elementary in the extreme, its importance lies in the way it
illustrates the concept of cause and effect. We would not feel warmer if the radiator