Date post: | 12-Apr-2016 |
Category: |
Documents |
Upload: | celinka-chun |
View: | 28 times |
Download: | 10 times |
INTRODUCTION TO PHYSICAL CHEMISTRY
• It is the quantitative and theoretical study of the properties and structure of matter, and their relation to the interaction of matter and energy.
• Can be regarded as the study of the physical principles underlying chemistry – we wanted to know how and why materials behave as they do.
• The ultimate goal of physical chemistry is to provide a model (mathematical) for all chemistry.
What is Physical Chemistry?
The study of physical chemistry includes several disciplines:• Thermodynamics: relationship between energy interconversion by
materials, and the molecular properties.• Kinetics: rates of chemical processes• Quantum Mechanics: phenomena at the molecular level• Statistical Mechanics: relationships between individual molecules and the
bulk properties of matter• Spectroscopy: non-destructive interaction of light (energy) and matter, in
order to study chemical structure• Photochemistry – interaction of light and matter with the intent of
coherently altering molecular structure.
What is Physical Chemistry?
WHAT IS PHYSICAL CHEMISTRY?
variables , relationships, and laws
VARIABLES: an experimental parameter we can change or tweak
RELATIONSHIPS: existence of effects between variables
LAWS: an observation or generalization that is universal
PHYSICAL CHEMISTRY : Cause and Effect
Why do we feel cold when we enter an air-conditioned room?
- heat travels from our body into cold air surrounding us- causing our own energy content to lower - we feel more comfortableA transfer of energy occurs therefore a change. Without
the cause, the effect of feeling warmer could have not followed.
PHYSICAL CHEMISTRY : Physicochemical relationsips
Why does water get hot in a pot?- Water remains cold until we turn on the stove.
electrical energy – heat energy – absorbed by the waterThe temperature of the water does not increase much if
small amount of energy is consumedMathematical relationship: T = f (energy)
PHYSICAL CHEMISTRY : Quantitative and qualitative measurements
Will the bitterness in my coffee disappear if I add cream on it?
In any investigation, we look at first at qualitative relationships.
If I change variable x is there a response in variable y? (qualitative relationships)
How much of the response is caused? (quantitative relationships)
PHYSICAL CHEMISTRY: Observed and controlled variables
Does my TV get louder if I vary the volume control?- We vary the volume control, and as a response, our
ears experience increase in the sound level.- The magnitude of the noise and the position of the
volume knob are both variables, they represent different types:
Volume control: controlled variableAmount of noise: observed variable
PHYSICAL CHEMISTRY: Relationships and graphs
Physical Chemists often depict relationships between variables by drawing graphs:
RELATIONSHIP BETWEEN VARIABLES
h = constant x p
LAWS and the -1th Law of Thermodynamics
Why does a radiator feel hot to touch when it is “on” and cold when it is “off”?
ON – heat travels from radiator to our body
OFF – heat from our body travels to radiator
-1th law of thermodynamics: Heat always travels from hot to cold
The zeroth law of thermodynamics:How does a thermometer work?
ZEROth Law: If A and B are in thermal equilibrium, and B and C are also in thermal equilibrium, then A and C will be in thermal equilibrium.
UNITS OF MEASURE
DERIVED UNITS:
FORCE:
• unit of force in SI system is the newton (N)
• force required to give a mass of 1 kg an acceleration of 1 m/s2
ENERGY:
• SI unit of energy is the joule (J) (1 J = 1 N m)
• a non-SI unit of energy some chemist still use is the calorie
1 cal = 4.184 J
DERIVED UNITS:
PRESSURE:
• defined as force per unit area (p = F/A)
• SI unit of measure is the Pascal (Pa) 1Pa = 1 N/m2
1 bar = 100 kPa
1 atm = 101.325 kPa
1 atm = 1.01325 bar
1 atm = 760 torr
Atomic Mass, Molecular Mass, the Mole
1 amu is defined as equal to exactly 1/12 of the mass of 1 C-12 atom.
1 mole of any substance is the mass of that substance that contains as many atoms molecules, ions or any other entities as there are atoms in exactly 12 g of C-12.
1 mole of C-12 contains 6.0221367 X 1023 atoms (Avogadro’s number)
The molar mass of a substance is the mass in grams of 1 mole of the substance.