1. Energy and IMFs Main Concept:
Potential energy is associated with the interaction of molecules; as molecules draw near each other, they experience an attractive force.

2. IMF Review
Hydrogen Bonding
Energy and IMFs
Chemical
Process
Physical
Process
Interactions in Biological Molecules

3. Energy and IMFs
IMF Review
Hydrogen Bonding
Energy and IMFs

4. - Types of intermolecular forces:
- dipole-dipole: attractions b/w polar molecules
- dipole-induced dipole: attractions b/w polar and
nonpolar molecules
- induced dipole-induced dipole (dispersion):
attractions b/w nonpolar molecules

5. - All substances will manifest dispersion forces, and these forces are larger when molecules involved have more electrons or have a larger surface area (size of atoms/molecules)

6. - Hydrogen bonding  relatively strong type of intermolecular interaction occurring b/w hydrogen atoms covalently bonded to highly electronegative atoms (N, O, and F) attracted to negative ends of a dipole formed by electronegative atoms (N, O, and F) in a different molecule or a different part of same molecule
- When hydrogen bonding is present, even small molecules may have strong intermolecular attractions

7. - When intermolecular forces are broken, that is an endothermic process
ie. ice melting due to heat
- When intermolecular forces are formed, that is an exothermic process
ie. ice forming due to removal of heat

8. *known as solution formation
- When energy of separation is less than energy of formation (mixing), net reaction is exothermic
- When energy of separation is greater than energy of formation (mixing), net reaction is endothermic
endothermic
process
endothermic
process
exothermic
process
*known as solution formation

9. Chemical vs Physical Processes
Main Concept:
At the particulate scale, chemical processes can be distinguished from physical processes because chemical bonds can be distinguished from intermolecular interactions.

10. Chemical vs Physical Processes

11. - distinctions between chemical and physical processes relates to nature of change in molecular interactions
- Processes that involve breaking and/or formation of chemical bonds = chemical processes
- Processes involving only changes in weak intermolecular interactions, such as phase changes, are classified as physical processes

12. - gray areas exists between these two extremes
Ex: dissolution of a salt in water involves breaking ionic bonds and formation of interactions between ions and solvent
- magnitude of these interactions similar to covalent bond strengths, and so arguments can be made for classifying dissolution of salts as either a physical or chemical process.

13. Biological Interactions
Main Concept:
Noncovalent and intermolecular interactions play important roles in many biological and polymer systems.

14. Biological Interactions
Interactions in Biological Molecules

15. - In large biomolecules, noncovalent interactions may occur between different molecules or between different regions in same large biomolecule
- functionality and properties of molecules depend strongly on shape of molecule, which is largely dictated by noncovalent interactions
Ex: function of enzymes is dictated by structure, and properties of synthetic polymers are modified by manipulating chemical composition and structure