Chapter 7 Gases Liquids And Solids Chem 108

Front 1

Gas

Back 1

Consists of particles that are far apart and move rapidly and independently from each other.

Front 2

liquid

Back 2

consists of particles that are much closer together but are still somewhat disorganized since they can move about. the particles in a liquid are close enough that they exert a force of attraction on each other

Front 3

Solid

Back 3

consists of particles--atoms,molecules, or ions--that are close to each other and are often highly organized. the particles in a solid have little freedom of motion and are held together by attractive forces

Front 4

Whether a substance

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exists as a gas liquid or solid depends on the balance between the kinetic energy of its particles and the strength of the interactions between the particles

Front 5

properties of Gases Liquids and solids

Back 5

Property
Shape and Volume
Arrangement of particles
Density
Particle movement
Interaction between Particles

Front 6

Gas

Back 6

Consists of particles that are far apart and move rapidly and independently from each other.

Front 7

liquid

Back 7

consists of particles that are much closer together but are still somewhat disorganized since they can move about. the particles in a liquid are close enough that they exert a force of attraction on each other

Front 8

Solid

Back 8

consists of particles--atoms,molecules, or ions--that are close to each other and are often highly organized. the particles in a solid have little freedom of motion and are held together by attractive forces

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Whether a substance

Back 9

exists as a gas liquid or solid depends on the balance between the kinetic energy of its particles and the strength of the interactions between the particles

Front 10

properties of Gases Liquids and solids

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Property Gas
Shape and Volume expands to fill container
Arrangement of particles Randomly arranged disorganized and far apart
Density low (<0.01g/mL)
Particle movement very fast
Interaction between Particles None

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properties of Gases Liquids and solids

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Property Liquid
Shape and Volume a fixed volume that takes the shape of the container it occupies
Arrangement of particles Randomly arranged but close
Density High (1 g/mL)cubed
Particle movement moderate
Interaction between Particles strong

Front 12

properties of Gases Liquids and solids

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Property Solid
Shape and Volume a definite shape and volume
Arrangement of particles fixed arrangement
Density high(1-10g/mL)
Particle movement slow
Interaction between Particles verystrong

Front 13

properties of Gases Liquids and solids

Back 13

Property Liquid
Shape and Volume a fixed volume that takes the shape of the container it occupies
Arrangement of particles Randomly arranged but close
Density High (1 g/mL)cubed
Particle movement moderate
Interaction between Particles strong

Front 14

properties of Gases Liquids and solids

Back 14

Property Solid
Shape and Volume a definite shape and volume
Arrangement of particles fixed arrangement
Density high(1-10g/mL)
Particle movement slow
Interaction between Particles very strong

Front 15

Kinetic-molecular theory of Gases

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1 A gas consists of particles-atom or molecules-that move randomly.
2 the size of gas particles is compared to the space between the particles.

Front 16

Kinetic-molecular theory of Gases

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3 Because the space between gas particles is large, gas particles exert no attractive forces on each other
4 the kinetic energy of gas particles increases with increasing temperature

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Kinetic-molecular theory of Gases

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5 when gas particles collide with each other, they rebound and travel in new directions when gas particles collide with the walls of a container, they exert a pressure

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Pressure (P) is the force (F) exerted per unit area (A)

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pressure= Force/area or
F
__
A

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Atmosphere (atm) and millimeters of mercury (mm Hg)

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1 atm = 760. mm Hg or one torr
in the US the common pressure unit is pounds per square inch (psi) where 1 atm=14.7 psi

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psi-atm conversion factor (we do not want psi)

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1 atm/14.7psi

3000psi x 1 atm /14.7 psi = 204 atm

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psi-mmHg conversion factor (we do not want psi)

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760. mmHg/14.7 psi (unwanted)

3000psi x 760. mmHg/14.7 psi = 155,000 mm Hg

Front 22

Sphygmomanometer is used to take blood pressure

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systolic pressure is 100-120
diastolic pressure 60-80vsystolic pressure of 140 or greater or diastolic pressure is 90 or greater is said to have Hypertension (high blood Pressure)

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Four variables are important in discussing the behavior of gases

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pressure (P)
Volume (V)
Temperature (T) and number of moles (n)

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Gas Laws

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Boyle's law relates pressure and volume
Charles's law relates volume and temperature
Gay-Lussac's law relates pressure and temperature

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Boyle's law

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For a fixed amount of gas at constant temperature, the pressure and volume of gas are inversely related

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When two quantities are inversely related one quantity increases as the other decreases

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The product of the two quantities, however, is a constant symbolized by k
When pressure increases Volume decreases
Pressure x Volume =constant

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Thus, if the volume of a cylinder of gas is halved, the pressure of the gas inside the cylinder doubles

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The same number of gas particles occupies half the volume and exerts two times the pressure

Front 28

P1 =10.0 atm
V1 = 4.0 L V2 = 6.0 L
above knows
P2 + ? unknown

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P1 V1/V2=P2

10.0 atm x 4.0 L/6.0L Liters cancel
= 6.7 atm = P2 pressure decreased

Front 29

Charles's Law How the volume and temperature of a gas are related

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All gases expand when they are heated and contract when they are cooled

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Charles's law:

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for a fixed amount of gas at constant pressure, the volume of a gas is proportional to its Kelvin temperature

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Volume and temperature are proportional; that is as one quantity increases,

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the other increases as well. Thus dividing volume by temperature is a constant (k)
V X T
Temperature increases then Volume increases
V/T = k

Front 32

V1 = 0.50L
T1 = 25 degrees C T2 = -196 degrees C
V2 is the desired quantity

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K = C + 273
T1 = 25 C + 273 = 298K
T2 = -196 C = 77K
V1/T1 = V2/T2
V1xT2/T1
0.50 L 77K/298K K cancel = 0.13 L
temperature decreased volume decreased

Front 33

Gay-Lussac's Law

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for a fixed amount of gas at constant volume, the pressure of a gas is proportional to its Kelvin temperature

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Pressure and temperature are proportional

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that is, as one quantity increases the other increases. Thus, dividing the pressure by temperature is a constant (k)
P x T when temperature increases pressure increases P / T = k

Front 35

P1 = 80 psi
T1 = 18 C T2 =43 C
known quantities
desired quantity P2

Back 35

T1 =C + 273 = 18 C + 273 =291 K
T2 =C + 273 = 43 C + 273 + 316 K
P2 = P1T2 /T1 = 80psi x 316 K/ 291K k cancel = 87psi
since temperature increased so does volume

Front 36

All three gas laws-Boyle's, Charles's and Gay-Lussac' laws can be combined in a single equation, the combined gas law

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P1V1/T1 + P2V2/T2

Front 37

P1 = 760 mm Hg P2 = 540 mm Hg
T1 = 20 C T2 = -40 C
V1 222l known V2=? unknown
T1=C+273 =20 C + 273 = 293K
T2 =C + 273= -40 C + 273 =233

Back 37

P1V1/T1 = P1 V2 / T2
P1V1 T2/t1 P2 =V2
760mm Hg x 222 L x 233 K/293 K x 540 mm Hg K and mm Hg cancel = 248.5 L rounded to 250 L

Front 38

Avogadro's Law

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When the pressure and temperature are held constant, the volume of a gas is proportional to the number of moles present

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When the number of moles increases

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the volume increases
V/n = k
increasing the number of moles increases the volume of a gas

Front 40

V1 = 5.8 L V2 = 4.6 L
n1 = 0.25 mol known quantities
n2 = ? is unknown

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V1/n1=V2/n2
n1V2/V1
0.25 mol x 4.6 L:/5.8 L Liters are cancelled = 0.20 mol

Front 41

Avogadro's Law allows us to compare two gases by comparing their volumes

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often amounts of gas are compared at a set of standard conditions of temperature and pressure abbreviated as STP

Front 42

STP conditions are

Back 42

1atm (760 mm Hg) for pressure
273 K (0 C) for temperature
At STP one mole of any gas has the same volume, 22.4 L called the standard molar volume

Front 43

STP Same volume same number of particles

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1 mol N2 1 mol He
22.4 L 22.4 L
6.02x10ee23 particles same
28.0 g 4.0 g

Front 44

How many moles are contained in 2.0 l of N2 at standard temperature and pressure

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Conversion 22.4 L/1 mol or
1 mol / 22.4
2.0 L x 1mol/22.4 L liters cancel =0.089 mol of N2

Front 45

132.0 g CO2 known ? L of CO2

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132.0 g CO2 x 1 mol/44.0 g CO2 = 3.00 mol CO2
3.00 mol CO2 x 22.4L/1mol= 67.2 L CO2

Front 46

All four properties of gases ---pressure, volume, temperature and number of moles --can be combined into a single equation called the

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ideal gas law the product of pressure and volume divided by the product of moles and Kelvin temperature is a constant, called the universal gas constant symbolized by R

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PV/nT = R universal gas constant

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for atm: R = 0.821x L x atm / Mol x K
For mm Hg: R = 62.4 L x mm Hg/mol x K

Front 48

STP Same volume same number of particles

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1 mol N2 1 mol He
22.4 L 22.4 L
6.02x10ee23 particles same
28.0 g 4.0 g

Front 49

How many moles are contained in 2.0 l of N2 at standard temperature and pressure

Back 49

Conversion 22.4 L/1 mol or
1 mol / 22.4
2.0 L x 1mol/22.4 L liters cancel =0.089 mol of N2

Front 50

132.0 g CO2 known ? L of CO2

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132.0 g CO2 x 1 mol/44.0 g CO2 = 3.00 mol CO2
3.00 mol CO2 x 22.4L/1mol= 67.2 L CO2

Front 51

All four properties of gases ---pressure, volume, temperature and number of moles --can be combined into a single equation called the

Back 51

ideal gas law the product of pressure and volume divided by the product of moles and Kelvin temperature is a constant, called the universal gas constant symbolized by R

Front 52

PV/nT = R universal gas constant

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for atm: R = 0.821x L x atm / Mol x K
For mm Hg: R = 62.4 L x mm Hg/mol x K
Be careful to use the correct value of R for the pressure units in the problem you are solving

Front 53

How many moles of gas are contained in a typical human breath that takes in 0.50 L of air at 1.0 atm pressure and 37C

Back 53

P= 1.0 atm
V= 0.50 L
T = 37 C known n= mol unknown
37 C + 273 = 310
PV =nRT
PV/RT = n
1.0 atm x 0.50 L /0.821 L x atm/mol x K x 310 K = 0.0196 rounded to 0.020 mol

Front 54

A mixture of gas behaves like a pure gas

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each component of a gas mixture is said to exert a pressure called its partial pressure--Dalton's law describes this relationship

Front 55

Dalton's Law

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the total pressure (Ptotal) of a gas mixture is the sum of the partial pressures of its component gases
thus in 3 gases we have
ptotal = Pa + Pb+Pc

Front 56

Since liquids and solids are composed of particles that are much closer together

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a force of attraction exists between them

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Intermolecular forces are

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the attractive forces that exist between molecules

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There are three different types of intermolecular forces in covalent molecules, presented in order of increasing strength

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London dispersion forces
Dipole-dipole interactions
Hydrogen bonding

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London dispersion forces are very weak

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interactions due to the momentary changes in electron density in a molecule

Front 60

The weak interaction between these temporary dipoles constitutes London dispersion forces

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All covalent compounds exhibit London dispersion forces

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The larger the molecule

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the larger the attractive force between two molecules and the intermolecular forces

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Dipole-Dipole interactions

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are the attractive forces between the permanent dipoles of two polar molecules

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hydrogen bonding occurs when

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a hydrogen atom bonded to O, N, or F is eletrostacically attracted to an O, N, or F atom in another molecule

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Hydrogen bonds

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are the strongest of the three types of intermolecular forces

Front 65

Type of Force Relative strength
London dispersion weak
Dipole-dipole moderate
Hydrogen bonding strong

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exhibited by Example
all molecules CH4, H2CO H2O
molecules with a net dipole H2CO H2O
molecules with an O-H N-H or H-F bond H2O

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The stronger the intermolecular forces

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the higher the boiling and melting point

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When a liquid is placed in an open container, liquid molecules near the surface that have enough kinetic energy to overcome intermolecular forces escape to the gas phase

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this is called evaporation

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Evaporation is an endothermic process

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it absorbs heat from its surroundings

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Condensation is an exothermic process

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it gives off heat to the surroundings

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Vapor pressure

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is the pressure exerted by gas molecules in equilibrium with the liquid phase

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Vapor pressure

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increases with increasing temperature

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The normal boiling point of a liquid is the temperature

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at which its vapor pressure equals 760 mm Hg

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the stronger the intermolecular forces

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the lower the vapor pressure at any given temperature

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Viscosity

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is the measure of a fluids resistance to flow freely Viscosity makes a liquid feel thicker

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Surface tension

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is a measure of the resistance of a liquid to spread out The stronger the intermolecular forces the stronger surface molecules are pulled down toward the interior of a liquid and the higher the surface tension

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Solids can be either

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crystalline or amorphous

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a crystalline solid

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has a regular arrangement of particles-atoms, molecules, or ions---with a repeating structure

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an amorphous solid

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has no regular arrangements of its closely packer particles

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There are four types of crystalline solids

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ionic example salt NaCl
molecular ice
network Sand SiO2
metallic Copper Cu

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ionic solid is composed of

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oppositely charged ions

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a molecular solid

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is composed of individual molecules arranged regularly

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network solid is composed

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of a vast number of atoms covalently bonded together forming sheets of three dimensional arrays

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a metallic solid can be though of as

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a lattice of metal cations surrounded by a cloud of electrons that move freely
because of these loosely held delocalized electrons metal conduct electricity and heat

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Amorphous solids

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have no regular arrangement of particles--examples are rubber, glass, and most plastics

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Converting a solid to a liquid

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is called melting

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converting a liquid to a solid

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is called freezing

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Converting a liquid to a gas is called

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vaporization

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Converting a gas to a liquid

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is called condensation

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Occasionally a solid phase forms a gas phase without passing through the liquid state

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this is called sublimation the reverse process is called deposition