1. Properties of Gases

• In organized soccer, a ball that is properly inflated will rebound faster and travel farther than a ball that is under-inflated. If the pressure is too high, the ball may burst when it is kicked. You will study variables that affect the pressure of a gas.

What factors affect the pressure of the air inside the ball? What causes the pressure in the ball? 2.

• • Compressibilityis a measure of how much the volume of matter decreases under pressure.

• • When a person collides with an inflated airbag, the compression of the gas absorbs the energy of the impact.

3.

• • Gases are easily compressed because there is a lot of space between the particles in a gas.

• • • • The distance between particles in a gas is much greater than the distance between particles in a liquid or solid.

• • • • Under pressure, the particles in a gas are forced closer together.

4.

• • At room temperature, the distance between particles in an enclosed gas is about 10 times the diameter of a particle.

5.

• The amount of gas, volume, and temperature are factors that affect gas pressure.

• The relationships between these factors are described by GAS LAWS.

6.

• • The four variables used to describe a gas and their common units are

• • • pressure ( P ) in kilopascals or atm

• • • volume ( V ) in liters

• • • temperature ( T ) in kelvins

• • • the number of moles ( n ).

7.

• Avogadros Law- n P

• • You can use kinetic theory to predict and explain how gases will respond to a change of conditions.

• • If you inflate an air raft,

• • for example, the pressure

• • inside the raft will increase.

8.

• • Collisions of particles create pressure.

• • Increasing the number of gas particles increases the number of collisions, which is why the gas pressure increases.

• • Avogadros Law- n P

• • directly proportional

9.

• • If the gas pressure increases until it exceeds the strength of an enclosed, rigid container, the container will burst.

10. Not for the faint at heart 11.

Aerosol Spray Paint

Gas flows from a region of higher pressure to a region of lower pressure

12.

• Boyles law - V P orV P

• • You can raise the pressure exerted by a contained gas by reducing its volume.

• • The more a gas is compressed, the greater the pressure of the gas.

13.

• When volume decreases, particles do not have to travel as far before they hit the side of the container.

14.

• This causes more collisions and therefore more pressure.

15.

• Boyles Law- V P

• Indirect relationship

16.

• • When the volume of the container is halved, the pressure the gas exerts is doubled.

17.

• Gay-Lussacs Law- T P

• • An increase in the temperature of an enclosed gas causes an increase in its pressure.

• • As a gas is heated, the average kinetic energy of the particles in the gas increases.

18.

• Gay-Lussacs Law- T P

• • An increase in the temperature of an enclosed gas causes an increase in its pressure.

• • Faster-moving particles strike the walls of their container more often and with more energy.

19.

• Gay-Lussacs Law - T P

• • An increase in the temperature of an enclosed gas causes an increase in its pressure.

• • Pressure = force/area

• • So more force (harder & more frequent collisions) makes more pressure.

20.

• • When the Kelvin temperature of the enclosed gas doubles, the pressure of the enclosed gas doubles.

21.

• • Gay-Lussacs Law - T P

• • Directly proportional

22.

Gay-Lussacs Law: T P

• • • As the temperature of an enclosed gas increases, the pressure increases, if the volume is constant.

23.

A pressure cooker demonstrates Gay-Lussacs Law.

24.

Charles Law- T V

When a gas is heatedat constant pressure , the volume increases.

25.

Charles Law- T V

• • • As the temperature of an enclosed gas increases, the volume increases, if the pressure is constant.

• • • T ,V

26.

As the temperature of the water increases, the volume of the balloon increases.

27.

The KMT explains Gay-Lussacs Law-

as temperature increases particles movefaster, so they will collide more often andharder, increasing the pressure.

In orderto maintain constant pressure,the volume will need to increase!

Charles Law- T V

if pressure is constant

28.

Thecombined gas lawdescribes the relationship among the pressure, temperature, and volume of an enclosed gas.

29.

• The combined gas law allows you to do calculations for situations in which only the amount of gas is constant.

30.

• 1.Compared to liquids and solids, gases are easily compressed because the particles in a gas

• • attract each other.

• • are spaced relatively far apart.

• • are very small.

• • repel each other.

14.1 Section Quiz. 31.

• 2.Gas pressure is affected by

• • temperature, volume, and the amount of the gas.

• • temperature, volume, and the molar mass of the gas.

• • phase diagram, volume, and the size of the container.

• • temperature, phase diagram, and the mass of the gas container.

14.1 Section Quiz. 32.

• 3. For gases, the SI units for volume ( V ), pressure ( P ), and temperature ( T ) are, respectively,

• • liters, kilopascals, and C.

• • liters, kilopascals, and kelvins.

• • cm 3 , kilopascals, and kelvins.

• • liters, atmospheres, and C.

14.1 Section Quiz.