Chapter 12: Liquids & Solids Flashcards Preview

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Flashcards in Chapter 12: Liquids & Solids Deck (35)
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1
Q

Surface tension

A

Elastic force in the surface of a liquid

The amount of energy required to strech or increase the surface of a liquid by a unit area

Strong intermolecular forces = high surface tension

2
Q

Capillary action

A

More pronounced in a cylinder with small diameter

Miniscus forms either a concave (U-shaped) or convex (dome-shaped) curve at the liquid’s surface due to cohesion and adhesion

3
Q

Cohesion

A

Attractions between like molecules

4
Q

Adhesion

A

(Think tape: sticks to other material)

Attractions between unlike molecules

5
Q

Viscosity

A

A measure of a fluid’s resistance to flow

As T increases, viscosity decreases

6
Q

Vapor pressure

A

Depends upon magnitude of intermolecular forces

High vapor pressure = volatile substances

7
Q

Evaporation or vaporization

A

Change of phase: from liquid to gas

*Initially more rapid than condensation

8
Q

Condensation

A

Change of phase: gas to liquid

Can occur when gas strikes liquid surface and becomes trapped by intermolecular forces

*Initially slower than evaporation

9
Q

Dynamic equilibrium

A

When a forward process and reverse process occur at the same rate

Both processes going on (dynamic)

Number of gas molecules in the gas phase at any point in time doesn’t change (equilibrium)

10
Q

Equilibrium vapor pressure

A

The pressure exerted by the molecules that have escaped to the gas phase, once the pressure has stopped increasing

11
Q

Boiling point

A

The temperature at which its vapor pressure equals the external pressure

12
Q

Melting point

A

The temperature at which the energies of individual particles enable them to break free of their fixed positions in the solid – allowing them to flow past one another

Stronger intermolecular forces = higher melting point

13
Q

Crystalline solid

A

Rigid and long-range internal order/structure of molecules/particles

14
Q

Lattice structure

A

Arrangement of particles in a crystalline solid

Depends on the nature and size of the particles involved

15
Q

Unit cell

A

The basic repeating structural unit of a crystalline solid

16
Q

Lattice point

A

Each particle within a unit cell

17
Q

Simple/primitive cubic cell

A

8 lattice points (particles)

1/8 (8 particles) = 1 whole particle in simple cubic cell

Coordination number: 6

18
Q

Coordination number

A

The number of atoms/particles surrounding an atom/particle in a crystal lattice

Larger coordination # = more tightly packed cell

19
Q

Body-centered cubic cell

A

9 lattice points (8 corners, 1 center)

1/8 (8 corner lattice points) + 1 = 2 whole particles in cell

Coordination number:
8

20
Q

Face-centered cubic cell

A

8 corners + 6 sides = 14 particles/lattice points

1/8 (8 corners) + 1/2 (6 sides) = 4 whole particles in cell

Coordination number: 12

21
Q

Molar heat of vaporization ΔHvap

A

Amount of heat required to vaporize a mole of substance at its boiling point

kJ/mol

22
Q

Critical temperature TC

A

Particular temperature at which a substance in its gas phase cannot be liquefied, no matter how great the applied pressure

23
Q

Critical pressure CP

A

The minimum pressure that must be applied to liquefy a substance at its critical temperature

24
Q

Supercritical fluid

A

A fluid at a temperature and pressure that exceed critical temperature and pressure

Temperatures above critical temperature = no longer a distinction between gas and liquid phases, there’s simply a fluid (plasma)

Used as solvents in many industrial applications

25
Q

Fusion

A

Melting – phase change of solid to liquid

26
Q

Freezing point

A

AKA melting point

Temperature at which solid and liquid phases coexist at equilibrium

27
Q

Normal melting/freezing point

A

The temperature of melting/freezing at 1 atm

28
Q

Molar heat of fusion ΔHfus

A

Energy (kJ/mol) required to melt 1 mole of a solid

*MUCH smaller than ΔHvap because solids & liquids are more alike than liquids & gases

29
Q

Supercooling

A

Liquid is temporarily cooled to below its freezing point

Occurs when heat is removed from a liquid so rapidly that the molecules literally have no time to assume the ordered structure of a solid

Unstable - stirring or adding small “seed” crystal solidifies sample quickly

30
Q

Sublimation

A

Phase change from solid to gas

Thus, solids can have vapor pressure

31
Q

Deposition

A

Phase change – vapor phase to solid phase

32
Q

Molar enthalpy of sublimation ΔHsub

A

Amount of energy (kJ/mol) required to sublime 1 mole of a solid

ΔHsub = ΔHvap + ΔHfus

33
Q

Phase diagram

A

Summarizes conditions (T & P) at which a substance exists in its various phases

Separated by phase boundary lines

34
Q

Triple point

A

The point on a phase diagram at which all three phase boundary lines meet

The only combination of T & P at which all three phases of a substance can be in equilibrium with each other

35
Q

Critical point

A

Point at which the liquid-vapor phase boundary line abruptly ends

This corresponids with the critical temperature and pressure (CT and CP)