STATE OF MATTER STATE OF MATTER MATTER MATTER • Anything that occupies space and has mass. Anything that occupies space and has mass. • Include things we can see and touch (water, trees) as well as things we Include things we can see and touch (water, trees) as well as things we can’t see (air). can’t see (air). THREE STATES OF MATTER •All substances/matter can exist in 3 states : solid, liquid and gas. •Solid - molecules are held close together in an orderly fashion with little freedom of motion. •Liquid - molecules are close together but are not held so rigidly in position and can move past one another. •Gas - molecules are separated by distances that are large compared with the size of the molecules.
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STATE OF MATTERSTATE OF MATTER
MATTER MATTER • Anything that occupies space and has mass.Anything that occupies space and has mass.• Include things we can see and touch (water, trees) as well as things we can’t see (air).Include things we can see and touch (water, trees) as well as things we can’t see (air).
THREE STATES OF MATTER•All substances/matter can exist in 3 states : solid, liquid and gas.
•Solid - molecules are held close together in an orderly fashion with little freedom of motion.
•Liquid - molecules are close together but are not held so rigidly in position and can move past one another.
•Gas - molecules are separated by distances that are large compared with the size of the molecules.
The three states of matter are The three states of matter are interconvertableinterconvertable.. The physical properties of a substance depends on the state of the The physical properties of a substance depends on the state of the
substance. When a substance undergoes a change in state, many of its substance. When a substance undergoes a change in state, many of its physical properties change.physical properties change.
THE GASEOUS STATETHE GASEOUS STATE Under certain condition of pressure & temp., most substances can Under certain condition of pressure & temp., most substances can
exist in any one of the three state of matter.exist in any one of the three state of matter. E.g. water - solid :ice ; liquid : water ; gaseous : steam / water vaporE.g. water - solid :ice ; liquid : water ; gaseous : steam / water vapor In gases - molecular motion is totally random, forces of interaction In gases - molecular motion is totally random, forces of interaction
between molecules are so small, each molecules moves freely and between molecules are so small, each molecules moves freely and essentially independently of other molecules.essentially independently of other molecules.
SUBSTANCES THAT EXIST AS GASESSUBSTANCES THAT EXIST AS GASES Under normal condition of pressure & temp. (1 atm , 25Under normal condition of pressure & temp. (1 atm , 25ooC), elements C), elements
that exist as gases are:that exist as gases are: The noble gases (Group 8A elements) : He, Ne, Ar, Kr, Xe, Rn - The noble gases (Group 8A elements) : He, Ne, Ar, Kr, Xe, Rn -
monatomic species.monatomic species. Hydrogen, nitrogen, oxygen, fluorine, and chlorine - exist as diatomic Hydrogen, nitrogen, oxygen, fluorine, and chlorine - exist as diatomic
molecules : Hmolecules : H22, N, N22, O, O22, F, F22, Cl, Cl22..
Allotrope of oxygen, Ozone (OAllotrope of oxygen, Ozone (O33))..
Compounds that exist as gases are HCl, CO, COCompounds that exist as gases are HCl, CO, CO22, NH, NH33, N, N22O, NO, O, NO, NONO22, SO, SO22, H, H22S, HCN, CHS, HCN, CH44..
Only OOnly O22 essential for our survival. essential for our survival. HH22S, HCN - deadly poisons.S, HCN - deadly poisons. CO, NOCO, NO22, SO, SO22, O, O3 3 - less toxic. - less toxic. He, Ne, Ar - chemically inert.He, Ne, Ar - chemically inert. Most gases are colorless except FMost gases are colorless except F22, Cl, Cl22, NO, NO22
General Properties of gas ;General Properties of gas ; CompressibleCompressible Have low density (about 2 kg per mHave low density (about 2 kg per m33)) Diffuses quickly (mix thoroughly)Diffuses quickly (mix thoroughly) Fills up a container uniformly Fills up a container uniformly Exert pressure uniformly on all sides of a container Exert pressure uniformly on all sides of a container
independently of the height or depthindependently of the height or depth..
PRESSURE OF A GASPRESSURE OF A GAS Gas exert pressure on any surface with which they come into contact - gas Gas exert pressure on any surface with which they come into contact - gas
molecules are constantly in motion and collide with the surface.molecules are constantly in motion and collide with the surface. Instrument to measure atmospheric pressure : Instrument to measure atmospheric pressure : barometerbarometer - - Long tube filledLong tube filled with mercury (Hg) is inverted into a dish of mercury.with mercury (Hg) is inverted into a dish of mercury. -Atm. pressure pushing on the surface of the Hg -Atm. pressure pushing on the surface of the Hg
in the tube is proportional to atmospheric pressure.in the tube is proportional to atmospheric pressure.
-- Height of Hg (h) Height of Hg (h) atm pressure. atm pressure.
h Atmospheric pressure
A second type of barometer, a A second type of barometer, a manometermanometer has two arms, one opened has two arms, one opened to the atmosphere and one closed or connected to a container filled to the atmosphere and one closed or connected to a container filled with gas. The pressure exerted by the atmosphere or by gas in a with gas. The pressure exerted by the atmosphere or by gas in a container is proportional to the difference in the mercury levels (h).container is proportional to the difference in the mercury levels (h).
The std atmospheric pressure (1 atm) is equal to The std atmospheric pressure (1 atm) is equal to the pressure that supports a column of mercury the pressure that supports a column of mercury exactly 760 mm (76 cm) high at 0exactly 760 mm (76 cm) high at 0ooC at sea level.C at sea level.
1 atm = 760 mmHg1 atm = 760 mmHg (mmHg represents pressure (mmHg represents pressure exerted by a column of mercury 1 mm high)exerted by a column of mercury 1 mm high)
SI Units - Pascals, Pa : Pressure =force/ areaSI Units - Pascals, Pa : Pressure =force/ area 1 Pa = 1 N/m1 Pa = 1 N/m22
1 atm =101,325 Pa =1.01325 x101 atm =101,325 Pa =1.01325 x105 5 Pa =1.01325 x10Pa =1.01325 x102 2 kPa.kPa.
THE GAS LAWSTHE GAS LAWSImportant generalizations regarding the macroscopic behavior of gaseous Important generalizations regarding the macroscopic behavior of gaseous
substances.substances.
1. 1. The Pressure -Volume Relationship : Boyle’s LawThe Pressure -Volume Relationship : Boyle’s Law-studied by Robert Boyle in 17th century.-studied by Robert Boyle in 17th century.
Volume of a fixed amount of gas maintained at constant temperature isVolume of a fixed amount of gas maintained at constant temperature is
inversely proportional to the gas pressure inversely proportional to the gas pressure
VV 1/P, 1/P, : proportional to: proportional to
or V = kor V = k11 x 1/P k x 1/P k11: proportionality constant: proportionality constant
PV = kPV = k11
For a given sample of gas under two diff sets of conditions at constantFor a given sample of gas under two diff sets of conditions at constant
temp. : temp. : PP11VV11 = k = k11 = P = P22VV22
P (atm)
1/V
0.6
0.3
2 4
P versus V graph at constant temp.: Volume of gas doubles as the pressure is halved.
P (atm)
V (L)
P versus 1/V
The Temperature-Volume Relationship : The Temperature-Volume Relationship : Charles’ LawCharles’ Law
At constant pressure, the volume of a gas sample expands when At constant pressure, the volume of a gas sample expands when heated and contracts when cooled.heated and contracts when cooled.
Study on the temp. – vol. relationship at various pressure showed that :Study on the temp. – vol. relationship at various pressure showed that :
• At any given pressure, the plot of vol. vs temp. yields a straight At any given pressure, the plot of vol. vs temp. yields a straight line.line.
• Extending the line to zero vol., the intercept on temp. axis is -Extending the line to zero vol., the intercept on temp. axis is -273.15 273.15 ooC (absolute temperature)C (absolute temperature)
V
T (oC)-273.15
P1
P2
P3
P4
Lord Kelvin identified the temp. -273.15 Lord Kelvin identified the temp. -273.15 ooC as C as theoretically the lowest attainable temptheoretically the lowest attainable temp., ., calledcalled absolute zero.absolute zero.• absolute temp. scaleabsolute temp. scale, , now callednow called Kelvin Kelvin
temp. scale.temp. scale.
Absolute zero : Absolute zero : 0 K = -273.150 K = -273.15ooC C 273.15 K = 0273.15 K = 0ooCC 373.15 K = 100373.15 K = 100ooCC
Relationship between Relationship between ooC and K:C and K:T (K) = t(T (K) = t(ooC) +273.15C) +273.15ooCC
Charles’ Law states that : Charles’ Law states that : the vol. of a fixed amounts of a gas maintained at the vol. of a fixed amounts of a gas maintained at constant pressure is directly proportional to the absolute temp. of the gas.constant pressure is directly proportional to the absolute temp. of the gas.
Under 2 diff. sets of conditions for a given sample of gas at constant Under 2 diff. sets of conditions for a given sample of gas at constant pressure :pressure :
VV11 / T / T11 = k = k22 = V = V22 / T / T22
VV11 / T / T1 = 1 = VV22 / T / T2 2
VV11, , VV2 2 are volumes of the gases at temp. Tare volumes of the gases at temp. T11 , T , T2 2 (both in kelvins).(both in kelvins).
V TV = k2T or V/T = k2
k2 is proportionality constant.
The Volume – Amount Relationship : Avogadro,s LawThe Volume – Amount Relationship : Avogadro,s Law Amedeo Avogadro – complemented the studies of Boyle, Charles and Amedeo Avogadro – complemented the studies of Boyle, Charles and
Gay-Lussac. He published a hypothesis that statedGay-Lussac. He published a hypothesis that stated : :
• At the same temp. and pressure, equal volumes of different gases contain At the same temp. and pressure, equal volumes of different gases contain the same number of molecules (or atoms if the gas is monatomic).the same number of molecules (or atoms if the gas is monatomic).
• The volume of any given gas must be proportional to the number of The volume of any given gas must be proportional to the number of molecules present;molecules present;
V V n n V = kV = k33n where n represents the number of moles and n where n represents the number of moles and
kk33 is the proportionality constant. is the proportionality constant.
Avogadro’s Law – Avogadro’s Law – at constant pressure and at constant pressure and temp., the vol. of a gas is temp., the vol. of a gas is directly proportional to the number of directly proportional to the number of moles of the gas presentmoles of the gas present..
The Ideal Gas Equation.The Ideal Gas Equation.
Boyle,s Law : V Boyle,s Law : V 1/P (at constant n and T) 1/P (at constant n and T) Charles’ Law : V Charles’ Law : V T (at constant n and P) T (at constant n and P) Avogadro’s Law:Avogadro’s Law: V V n (at contant P and T) n (at contant P and T)
Combine all three expressions : Combine all three expressions : V V nT / P nT / P = RnT/P, = RnT/P,
R, the proportionality constant is called the gas constant.R, the proportionality constant is called the gas constant.
Ideal gas – a hypothetical gas whose pressure- volume-temp. behavior can be completely accounted for by the ideal gas equation. The molecules of an ideal gas do not attract or repel one another, and their vol. is negligible comparedwith the volume of the container.
To apply the ideal gas equation to a real system, we must evaluate the To apply the ideal gas equation to a real system, we must evaluate the gas constant, R.gas constant, R.
At 0At 0ooC (273.15K) and 1 atm pressure, many real gas behave like an C (273.15K) and 1 atm pressure, many real gas behave like an ideal gas. Exp. show that under these conditions, 1 mole of an ideal ideal gas. Exp. show that under these conditions, 1 mole of an ideal gas occupies 22.414L.gas occupies 22.414L.
The conditions 0The conditions 0ooC (273.15K) and 1 atm pressure are called C (273.15K) and 1 atm pressure are called standard standard temp. and pressuretemp. and pressure (STP). (STP).
From From PV = nRTPV = nRT R = PV/nTR = PV/nT =( 1 atm)(22.414L)=( 1 atm)(22.414L) = 0.082057 L.atm/K.mol= 0.082057 L.atm/K.mol (1 mol)(273.15K)(1 mol)(273.15K)
For most calculations, use R=0.0821 L.atm/K.mol and For most calculations, use R=0.0821 L.atm/K.mol and the molar volume of a gas at STP as 22.4L.the molar volume of a gas at STP as 22.4L.
When pressure. volume, temp. and amount change, a modified When pressure. volume, temp. and amount change, a modified form of equation must be employed, which involves initial and form of equation must be employed, which involves initial and final conditions.final conditions.
If If nn11 = n = n2 2 as is usuallyas is usually the case because the amount of gas the case because the amount of gas normally does not change,normally does not change,
PP11VV1 1 / T/ T11 = P = P22VV2 2 / T/ T22
Density CalculationsDensity Calculations
From the ideal gas equation ,From the ideal gas equation ,
PV = nRT we can calculate the density of gas.PV = nRT we can calculate the density of gas.
The number of moles of the gas, n, is given by :The number of moles of the gas, n, is given by :
n = m /n = m /M , M , m = mass of gas (grams) and m = mass of gas (grams) and MM is its molar is its molar massmass
Since density is mass per unit volume, Since density is mass per unit volume,
n/V = P / RT n/V = P / RT
m/Vm/VM = M = P / RTP / RT
We can write We can write d = d = m/V = m/V = PPMM
RTRT
Unit of gas density are usually grams per liter (g/L), rather than grams per Unit of gas density are usually grams per liter (g/L), rather than grams per mL (g/mL) : density of gases is very low at atmospheric condition.mL (g/mL) : density of gases is very low at atmospheric condition.
The Molar Mass of a Gaseous SubstanceThe Molar Mass of a Gaseous Substance
Molar Mass of a substance is found by examining its formula and Molar Mass of a substance is found by examining its formula and summing the molar masses of its component atoms (if the actual summing the molar masses of its component atoms (if the actual formula of the substance is known).formula of the substance is known).
For an unknown gaseous substance, an experiment is needed to For an unknown gaseous substance, an experiment is needed to determine the density value (or mass and volume data) at a known determine the density value (or mass and volume data) at a known temp. and pressure.temp. and pressure.
From d = From d = m/V = m/V = PPMM , , we getwe get
RTRT
MM = = dRTdRT
PP
Assignment 1Assignment 1
1)1) A Balloon of volume 0.55mL at sea level at pressure P=1 atm A Balloon of volume 0.55mL at sea level at pressure P=1 atm is allowed to rise to a height with P=0.40atm. If the temperature is allowed to rise to a height with P=0.40atm. If the temperature remains constant, find the final volume of the balloon.remains constant, find the final volume of the balloon.
2)2) A 550mL of Fluorine gas, FA 550mL of Fluorine gas, F2 2 is heated from 22is heated from 22C to 87C to 87C at C at constant pressure.What is its final volume?constant pressure.What is its final volume?
3)3) What is the volume of HWhat is the volume of H22 evolved when 1.20g of Mg react with evolved when 1.20g of Mg react with excess of HCl at STP.excess of HCl at STP.
4)4) A helium filled balloon has a volume of 6.15mA helium filled balloon has a volume of 6.15m33 at 14 at 14C and C and 762mmHg. If its volume expands to 6.37m762mmHg. If its volume expands to 6.37m33 and pressure falls to and pressure falls to 749mmHg. Find its final temperature?749mmHg. Find its final temperature?
5)5) A sample of carbon monoxide gas has a volume of 3.20mL at 125 A sample of carbon monoxide gas has a volume of 3.20mL at 125 C. Calculate it temperature when its occupy 1.547mL at C. Calculate it temperature when its occupy 1.547mL at constant pressure.constant pressure.
6.6. A gas sample at 25A gas sample at 25C and 0.862atm has a density of C and 0.862atm has a density of
2.26g/L Calculate its molar mass.2.26g/L Calculate its molar mass.
7.7. The density of a gas at STP is 1.960g/L.Determine its molar The density of a gas at STP is 1.960g/L.Determine its molar mass.mass.
8.8. What is the mass of Sulphur dioxide which has a volume of What is the mass of Sulphur dioxide which has a volume of 2.0L at 252.0L at 25C and 1 atm pressure.?C and 1 atm pressure.?
9.9. Calculate the relative mass of 3.0g of a gas at 100 Calculate the relative mass of 3.0g of a gas at 100 C and C and 0.9atm occupies of 2.0L0.9atm occupies of 2.0L
10.10. Find the volume of carbon dioxide formed when 20.0mL of Find the volume of carbon dioxide formed when 20.0mL of CO reacts with excess oxygen gas at a constant temperatute CO reacts with excess oxygen gas at a constant temperatute & pressure.& pressure.
