States of Matter

These flashcards cover key concepts from the chapter on states of matter, focusing on intermolecular forces, phase transitions, thermal analysis, and practical applications in pharmaceuticals.

What are the two types of intermolecular forces involved in molecular stability?

Cohesion (attraction of like molecules) and adhesion (attraction of unlike molecules).

What is the Clausius-Clapeyron equation used for?

To relate the vapor pressure and the absolute temperature of a liquid.

Define supercritical fluids.

States of matter that exist under high pressure and temperature with properties between those of liquids and gases.

What is the phase rule?

A relationship that determines the number of degrees of freedom in a system, defined by the equation F = C - P + 2 where C is the number of components and P is the number of phases.

How does temperature affect the vapor pressure of liquids?

As the temperature of a liquid increases, the vapor pressure also increases.

What are van der Waals forces?

Weak forces that include dipole-dipole interactions, dipole-induced dipole interactions, and London dispersion forces.

What is the significance of the critical temperature?

Above this temperature, it is impossible to liquefy a gas regardless of the applied pressure.

What happens during adiabatic expansion of a gas?

The gas cools as it expands without heat entering the system.

What is a eutectic point?

The point at which a mixture has the lowest melting temperature, and where multiple phases can coexist in equilibrium.

What technique can be used to measure solvent content in solid samples?

The Karl Fisher method.

In terms of phase diagrams, what does a tie line represent?

The tie line connects two phases in equilibrium, indicating their compositions.

What does differential scanning calorimetry (DSC) measure?

It measures heat flows and temperatures related to thermal transitions in materials.

What is the effect of pressure on the freezing point of water?

Increasing pressure lowers the freezing point of water.

Which intermolecular force is primarily responsible for high boiling points in water?

Hydrogen bonding.

What phenomenon results in the formation of a liquid crystalline state?

A state that is intermediate between liquid and solid, characterized by molecular order and mobility.

What is an example of a practical application of supercritical fluids?

Decaffeination of coffee using supercritical CO2.

What is the primary distinction between molecular crystals and ionic crystals?

Molecular crystals have lower melting points and are softer compared to hard and brittle ionic crystals.

How do polymorphs differ in terms of stability and melting points?

Polymorphs can have different stabilities and melting points even though they are chemically identical.

What methods are used to analyze phase changes in thermal analysis?

Methods like DSC, DTA, and TGA are used to characterize phase transitions.

What does amorphous mean in the context of solids?

A state where molecules are arranged randomly, compared to the ordered structure of crystalline solids.

What is the relationship between intermolecular forces and melting points of solids?

Stronger intermolecular forces lead to higher melting points.