Learning Targets:

5.1 I can describe the principles of Kinetic Molecular Theory I can describe what atmospheric pressure is I can describe how temperature related to motion Explain the difference between solids, liquids, and gases at the molecular level. I can interpret phase diagrams and describe the factors that affect changes of state

5.2 I can apply the Gas Laws to solve a given problem• I can convert between units of measurement for pressure and temperature• Apply the Gas Laws to solve a given problem• Identify the 4 variables that influence gases, and explain the relationships between:

• Pressure and Volume• Pressure and Temperature• Volume and Temperature

• Solve problems (including stoichiometry problems) using the Ideal Gas Law  

5.3 I am able to demonstrate the principles of thermochemistry Explain the relationship between energy & heat Calculate changes in heat & energy in chemical & physical processes Calculate heat & energy changes in phase changes. I can define heat within a system, specific heat, and heat capacity.

Unit 5Gas Laws & Thermochemistry

5.1: I can describe the principles of Kinetic Molecular Theory

Explain the difference between solids, liquids, and gases at the molecular level.

I can describe how temperature related to motion

I can describe what atmospheric pressure is I can interpret phase diagrams and describe

the factors that affect changes of state

Today:

Solids:Very low Kinetic Energy (KE) - particles are vibrating, but can’t move around

Have a fixed shape, fixed volume

Liquids: Have variable shape, but fixed volume

Low KE- particles can move around, but still stay very close together

Gases:Variable shape, variable volume

High KE- particles can move away from each other and take the shape of their container.

Kinetic Energy and States of Matter

Solid - very low kinetic energy (KE)

Liquid - low KE, particles can move around

Gas - high KE, particles move freely & randomly

Temperature – representation of Kinetic Energy

Pressure – The collisions acting against molecules

Volume- the space available for molecules to move in

N- the Number of molecules.

Factors that affect change in state

Units:TemperatureTemperature is really the measurement of Kinetic

Energy of the particles involved.

Kinetic Energy is due to the mass & the speed of the particles.

High temperature means that particles are moving at higher speeds.

Kelvin is the unit that we use to measure Kinetic Energy

Scales of Temperature

Celsius vs. Fahrenheit

0 °C = 32 °F 100 °C = 212 °F

F 9 5(C)32

C5 9(F 32)

Scales of Temperature

William Thompson a.k.a. Lord Kelvin

Absolute temperature scale Kelvin (K)

At 0 K all motion stops time stops

K C 273

Scales of Temperature

F 9 5(C)32

C5 9(F 32)

K C 273

Units: PressurePressure is the amount of force an object puts

upon a defined areaIn the case of gases, the Pressure can be

described as the collisions of the individual gas particles on the sides of the container.

area

forcepressure

KEY UNITS AT SEA LEVEL

101.325 kPa (kilopascal)

1 atm (atmosphere)

760 mm Hg

760 torr

14.7 psi

Atmospheric Pressure

At sea level 1 atm = 14.696 lb/in2

= 101.3 KPa (kilopascals)

= 760 mm Hg = 760 torr

(antiquated measure)

= 1,013.25 mbar (stupid US unit)

= 1.01325 bar

Atmospheric Pressure

Atmospheric pressure decreases rapidly with height.

Climbing to an altitude of only 5.5 km where the pressure is 500 mb, would put you above one-half of the atmosphere’s molecules.

Phase Diagrams

H2O218

Phase Diagrams

Triple point - where the (s), (l), and (g) co-exist

Critical point - where phase boundaries cease to exist

*

A supercritical fluid is any substance at a temperature and pressure above its critical point. It can diffuse through solids like a gas, and dissolve materials like a liquid.

Supercritical fluids are suitable as a substitute for organic solvents in a range of industrial and laboratory processes. Carbon dioxide and water are the most commonly used supercritical fluids, being used for decaffeination and power generation respectively

Kinetic Molecular Theory (KMT)

Kinetic energy derived from motion

KMT has three main tenets:

1. Random motion - no attractive or repulsive forces between particles

2. Newtonian Motion

3. All collisions are perfectly elastic

€

KEavg = 32 RT

Kinetic Molecular Theory (KMT)

Newton’s Laws of Motion

I. An object remains at rest/motion until an outside force acts upon it

II. F = ma

III. To every action there is an equal and opposite reaction