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• Experiment to develop the relationship between the pressure and volume of a gas.
Include: Boyle’s Law • Experiment to develop the relationship between
the volume and temperature of a gas.Include: Charles’ Law, Absolute zero, Kelvin scale, ideal gas
Additional KEY TermsInverse relationshipDirect relationship
BOYLE’S LAW:
The volume of a given amount of gas (held at a constant temperature) varies inversely with the pressure.
P α 1 V
Pre
ssur
e (k
Pa)
Volume (mL)
BOYLE’S LAW – Pressure vs. Volume
What will be the volume of 40 L of gas (held at a constant temperature) if the pressure is doubled? Reduced to 1/3rd ?
P α 1 V
1/3 α 1 1/3
2 α 1 2
1 = 3 1/3 120 L
20 L
PV = k
=
P1V1P2V2
P α 1 V
If 3 L of gas is initially at a pressure of 1 atm, what would be the new pressure required for a volume of 0.5 L?
6 atm of pressure will change 3 L of a gas at 1 atm to 0.5 L.
=
P1V1 P2V2
=
(1)(3) P2 (0.5)
A syringe contains 20 mL of a gas at 100 kPa. The pressure in the syringe is changed to 25 kPa. What is the new volume of the gas?
The gas will expand to 80 mL.
=
P1V1 P2V2
=
(100)(20) V2(25)
Absolute Zero
Jacques Charles (1746-1823) • Volume of gas changed with only 1oC change in temperature.
An increase of 273°C, doubled the volume.
V α T
CHARLES’S LAW: Volume of a given gas (held at a constant pressure) varies directly with the temperature
Temperature (oC)
Vol
ume
(mL
)
CHARLES’S LAW – Temp vs. Volume
William Thomson (1824-1907) • Created Kelvin Scale where –273°C is the lowest temperature possible or Absolute Zero.
“Hypothetical” – called an ideal gas model:• predicts that with zero kinetic energy comes zero volume.
TK = TC + 273 TC = TK - 273
Stated as “315 Kelvin”- no degrees.
Ideal Gas Model:• engaged in random motion (normal)• obey conservation of energy (normal)• non-interacting particles
(IMFs alter results)
Most real gases behave like “ideal gases,” butformula fails at lower temperatures OR higher pressures.
=
V1 V2
T2
T1 **All temperatures must be in Kelvin.
V α T V = k T
What is the new volume of a gas if 100 mL of the gas at 25°C is cooled to –25°C?
25°C + 273 = 298 K–25°C + 273 = 248 K
The new volume is 83.2 mL.
=
V1 V2
T2
T1
=
100 V2 -25 25
=
100 83.2 mL (248) 298
If the volume of a gas at –73°C is doubled to 48.0 L, calculate the final temperature in degrees Celsius.
400 K – 273 = 127°C
–73°C + 273 = 200 K
=
V1 V2
T2
T1
=
24.0
48.0 400 K (200)
•Boyle described the inverse relationship between the pressure and volume of a gas at a constant temperature.
•Charles described the direct relationship between the temperature and volume of a gas at a constant pressure.
•William Thomson (Lord Kelvin) developed the Kelvin temperature scale.
•At zero Kelvin (absolute zero) , the volume of a gas will theoretically be zero.
•When solving gas problems the temperature must always be converted to Kelvin.
CAN YOU / HAVE YOU?
• Experiment to develop the relationship between the pressure and volume of a gas.
Include: Boyle’s Law • Experiment to develop the relationship between
the volume and temperature of a gas.Include: Charles’ Law, Absolute zero, Kelvin scale, ideal gas
Additional KEY TermsInverse relationshipDirect relationship
