The Behaviour of Gases

Size: px

Start display at page:

Download "The Behaviour of Gases"

Stephen McCormick
5 years ago
Views:

of INTRAMOLECULAR FORCES physical changes: (dissolving, changing state, etc) breaking and forming of INTERMOLECULAR FORCES COMPARING SOLIDS LIQUIDS AND GASES

1 INTRAMOLECULAR VS. INTERMOLECULAR FORCES LEARNING GOAL: to understand why gases behave the way they do The Behaviour of Gases intramolecular chemical changes: breaking and forming of INTRAMOLECULAR FORCES physical changes: (dissolving, changing state, etc) breaking and forming of INTERMOLECULAR FORCES COMPARING SOLIDS LIQUIDS AND GASES SOLIDS: definite volume definite shape incompressible LIQUIDS definite volume no definite shape incompressible weak intermolecular forces strong intermolecular forces more disorder of molecules very ordered molecular arrangement possesses vibrational and rotational energy possesses vibrational energy only 1

GASES no definite volume, changes with a change in pressure or temperature no definite shape very compressible weakest (practically none) intermolecular forces KINETIC MOLECULAR THEORY OF GASES when

2 GASES no definite volume, changes with a change in pressure or temperature no definite shape very compressible weakest (practically none) intermolecular forces KINETIC MOLECULAR THEORY OF GASES when talking about gases, kinetic energy is important in explaining why they behave the way they do. high disorder possesses vibrational, rotational and translational energy FIVE POSTULATES OF THE KMT The volume of the gas particles is negligible compared to the volume of the container, because gas molecules are small and far apart. There are no intermolecular forces between particles Gas molecules are in constant straight line random motion When gas molecules collide with each other, no kinetic energy is lost THE KINETIC MOLECULAR THEORY DESCRIBES AN IDEAL GAS A gas behaves like an ideal gas when temperature is high, And pressure is low **temperature and pressure greatly affect the volume of a gas** The average kinetic energy of gas molecules is directly related to the temperature. The greater the temperature, the greater their average kinetic energy (the faster they move) 2

3 Let s talk a bit about temperature: Temperature is a measure of the average kinetic energy of the gas molecules The higher the temperature, the faster the molecules will move because they have more kinetic energy (the energy of motion) Temperature is increased by adding heat. Temperature is measured Celsius or Kelvins Converting Celsius to Kelvins Kelvin is absolute temperature.it has NO NEGATIVE VALUES Kelvin starts at 0, 0K is zero Kelvins To convert from celsius to kelvins, add 273. To convert from kelvins to celsius, subtract 273 slide over 25 C = 298 K ( ) 45 C = 228 K ( ) 320 K = 47 C ( ) Try these. Let s talk about pressure. Pressure is caused by the gas molecules bouncing around and hitting the walls of the container. The more often they hit the walls of the container, the higher the pressure. 3

4 Millimetres of Mercury (mmhg) Atmospheres (atm) Pascals.kilopascals (kpa) Units of Pressure 1.2 atm = kpa 110 kpa = 825 mmhg TRY THESE: 1 atm = 760 mmhg = kpa SI unit of pressure measurement: kpa Charles Law: the effect of temperature on gas volume SO HOW DOES TEMPERATURE AND PRESSURE AFFECT THE VOLUME OF A GAS? THE VOLUME OF A FIXED MASS OF A GAS VARIES DIRECTLY WITH ITS TEMPERATURE, AT CONSTANT PRESSURE At constant pressure, increasing the temperature causes the volume of a gas to INCREASE 4

Boyle s Law: the effect of pressure on the gas volume THE VOLUME OF A FIXED MASS OF A GAS VARIES INVERSELY WITH ITS PRESSURE, AT CONSTANT TEMPERATURE At constant temperature, increasing the pressure

5 Boyle s Law: the effect of pressure on the gas volume THE VOLUME OF A FIXED MASS OF A GAS VARIES INVERSELY WITH ITS PRESSURE, AT CONSTANT TEMPERATURE At constant temperature, increasing the pressure causes the volume of a gas to DECREASE Gay Lussac s Law: the effect of temperature on gas pressure THE PRESSURE OF A FIXED MASS OF A GAS VARIES DIRECTLY WITH ITS TEMPERATURE, AT CONSTANT VOLUME. At constant volume, increasing the temperature will increase the pressure of a gas Homework: Checkpoint 1 on Gases Checklist (also: review questions from Solutions Checklist: Checkpoint 15 and 16) 5

Name: Regents Chemistry: Notes: Unit 8 Gases.

Name: Regents Chemistry: Notes: Unit 8 Gases 1 Name: KEY IDEAS The concept of an ideal gas is a model to explain the behavior of gases. A real gas is most like an ideal gas when the real gas is at low