This course is concerned with how fundamental physical laws can be used to interpret and predict the effect of interactions within and between molecules. We will only concern ourselves with interactions described by classical physics. This encompasses all that was known of the fundamental laws which govern the way in which the physical world functions before the advent of special relativity and quantum mechanics. Although this means we will not be able to explain the structure of atoms and molecules (this is the domain of quantum mechanics) we will see that much of the behaviour at the microscopic scale can still be understood and interpreted using the classical physics we will cover here.

The course will begin by covering the dynamics of the particulate motion of molecules under external forces. This will occupy approximately four and a half lectures. Next we will deal with the dynamics of internal molecular motions; vibrational and rotational, which will take two and a half lectures. We will end up with two lectures dealing with electromagnetic interactions.

1.1 Lecture Contents

Dynamics of molecules treated as particles

* molecules as particles - the centre of mass;

* describing the molecular motion - particulate kinematics;

* why molecules move - Newton's Laws;

* the fundamental intermolecular force - Coulomb's Law;

* simple intermolecular interaction - the collision of ionised molecules;

* fundamental law of collisions - the conservation of linear momentum;

* the electrostatic force due to many ions - the principle of superposition;

* the dipole - the electrostatic field and field lines;

* moving charged particles in a field - the electrostatic work;

* the potential energy and potential in electrostatic fields;

* the dipole - drawing a potential map;

* the conservation of energy;

* applying the conservation of energy - molecular dissociation

* applying the conservation of energy - how can reactions occur?;

Dynamics of internal molecular motions - vibration

* simple harmonic motion - the dipole oscillator and bond stiffness;

* conditions for simple harmonic motion;

* stable and unstable equilibrium;

Dynamics of internal molecular motions - rotation

* describing rotational motion - rotational kinematics;

* torque and moment of inertia;

* torque on a dipolar molecule in a uniform electrostatic field;

* angular momentum and its conservation;;

* rotational oscillations;

* rotational work and potential energy;

* kinetic energy of rotation;

* the vibrating and rotating molecule;


* the magnetic field and Lorentz force;

* mass spectrometry ;

* the origin of magnetic fields - moving charge;

* rules for sketching the magnetic field;

* gyroscopic motion and NMR;

* the dipole oscillator - electromagnetic radiation;

Additional topics have been covered in this text, which are not examinable. These are indicated by being printed on a grey background.

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