Chapter 11 - IMFs, Liquids, & Solids Flashcards
-Understand & be able to describe the intermolecular attractive interactions (ion-dipole, dipole-dipole, London dispersion, hydrogen bonding) that exist between molecules or ions, & be able to compare the relative strengths of intermolecular attractions in substances based on their molecular structure or physical properties. -Understand the concept of polarizability. -Understand the concepts of viscosity & surface tension in liquids -Know the names of the various phase changes for a pure subs
Define “intermolecular forces”.
The forces that exist between molecules
11.1
Characteristic properties of substances can be understood in terms of the _____ of the particles of each state compared to the energy of the ____ between those particles.
Kinetic energy, intermolecular interactions
11.1
Gases
Consist of a collection of widely separated particles in constant, chaotic motion. The average energy of the attractions between the particles is much smaller than their average kinetic energy. The lack of strong attractive forces between particles allows a gas to expand to fill its container.
11.1
Liquids.
The IMF are stronger than in gases, and are strong enough to hold particles close together, making them more dense and far less compressible than gases.
Liquids have definite volume, but the attractive forces in liquids aren’t strong enough to keep the particles from sliding past one another, allowing any liquid to be poured, and thus take on the shape of whatever portion of the container it occupies.
11.1
Solids.
The IMFs are strong enough to hold particles close together & lock them in place. Not very compressible because the particles have little free space between them - “condensed phase”. Take up positions in a highly regular 3D pattern (crystalline). Rigid. Units (ions/molecules) that form the solid possess thermal energy & vibrate in place. Vibrational motion increases in amplitude as a solid is heated- energy may increase to the point that the solid melts or sublimes.
11.1
The state of a substance depends largely on…..
the balance between the kinetic energies of the particles and the interparticle energies of attraction.
Kinetic energies (depend on temperature) tend to keep particles apart and moving, while the interparticle attractions tend to draw the particles together.
Gases at room temp have weaker IMFs than those that’re liquids, liquids weaker than those that are solids
11.1
We can change a substance from one state to another by heating or cooling, which changes the ___ of the particles.
Average kinetic energy
11.1 - Give It Some Thought (p. 439)
How does the energy of attraction between particles compare with their kinetic energies in (a) a gas, (b) a solid?
(a) Energy of attraction < kinetic energies
(b) Energy of attraction > kinetic energies
