# Properties of GasesPage 1

Slide 1

Gases

Slide 2

## The Nature of Gases

Gases expand to fill their containers

Gases are fluid – they flow

Gases have low density

1/1000 the density of the equivalent liquid or solid

Gases are compressible

Gases effuse and diffuse

Slide 3

## Ideal Gases

Ideal gases are imaginary gases that perfectly

fit all of the assumptions of the kinetic molecular theory.

Gases consist of tiny particles that are

far apart relative to their size.

Collisions between gas particles and between

particles and the walls of the container are

elastic collisions

No kinetic energy is lost in elastic

collisions

Slide 4

Ideal Gases (continued)

Gas particles are in constant, rapid motion.

They therefore possess kinetic energy, the

energy of motion

There are no forces of attraction

between gas particles

The average kinetic energy of gas

particles depends on temperature, not

on the identity of the particle.

Slide 5

## Pressure

Pressure is the force created by the collisions

of molecules with the walls of a container

Slide 6

## Standard Pressure

1 standard atmosphere (atm)

101.3 kPa (kilopascals)

14.7 lbs/in2

760 mm Hg (millimeters of mercury)

760 torr

Slide 7

## Measuring Pressure

The first device for measuring atmospheric

pressure was developed by Evangelista Torricelli

during the 17th century.

The device was called a “barometer”

Baro = weight

Meter = measure

Slide 8

## An Early Barometer

The normal pressure due to the atmosphere at sea level can support a column of mercury that is 760 mm high.

Slide 9

## The Kelvin Scale

Slide 10

Standard Temperature and Pressure “STP”

Either of these:

273 Kelvin (273 K)

0 C

And any one of these:

1 atm

101.3 kPa

14.7 lbs/in2 (psi)

760 mm Hg

760 torr