Man's physical universe

xanabras

UNIT IV

SECTION 1

MATTER IN THE GASEOUS STATE EXHIBITS MANY

INTERESTING PHYSICAL PROPERTIES

Introduction.

It seems almost incredible that the idea of the existence of matter

in the gaseous state was unknown until the past few hundred years.

Man lives in a gaseous ocean and breathes air which is a mixture of

gases.

There Are Two Types of Properties.

Matter is described in terms of its properties. There are two types

of properties, physical and chemical. Physical properties are those whose

manifestation appears to be unaccompanied by any change of composition.

Thus the freezing- and boiling-points ^ of water are physical

properties. The color and crystalline form of sugar are other examples

of physical properties.

Such properties as color, odor, taste, density, solubility, hardness,

ductility, expansibility, melting- and boiling-points, heat and electrical

conductivity, and specific heat are physical properties.

The second group of properties, chemical properties, are those which

express the capacity of a material for being transformed into other materials.

Thus the ability of gasoline or of wood to burn, or of iron to rust,

is a chemical property.

Chemical properties tell with what a material reacts (if the change

involves a reaction with other substances), under what conditions it

reacts, what materials are produced by the change, how much of the materials

are involved in the change, and how much energy is used up or evolved

in the process.

A Knowledge of the Properties of Matter Is Important.

Scientists spend a great deal of time in observing and measuring

the properties of matter. The properties of matter determine its

' The freezing- and boiling-points of lir4uids are those temperatures (points on thermometers)

at which liquids freeze or boil, respectively.

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