Gases have no definite shape or volume, and their particles move in random motion with little attraction to one another. The behavior of gases is described by various gas laws relating the gas's pressure, volume, temperature, and amount. Specifically, Boyle's law states that pressure and volume are inversely proportional at constant temperature; Charles's law specifies that volume and temperature are directly proportional at constant pressure; and Avogadro's law establishes that volume and amount are directly proportional at constant temperature and pressure.

1. BEHAVIOR OF
GASES

2. WHAT IS A GAS?

3. GAS
• a substance or matter in a state in which it will expand freely to fill
the whole of a container, having no fixed shape
• Gases have the following characteristics: No definite shape (takes the
shape of its container) No definite volume. Particles move in random
motion with little or no attraction to each other.
1. NO definite shape
2. NO definite volume
3. Particles move in random motion
4. No attraction to each other

4. • The four variables that describe a gas
•Pressure (symbol: p or P) is the amount of force
applied perpendicular to the surface of an object per unit area.
• 760 mmHg, 760 Torr, and 1 Atm
formula p=F/A
Where p = pressure
F = Force
A = Area of the space contact

5. •Temperature (symbol: T) (units: 273 kelvin)
• the perceptions of hotness and coldness.
The most common scales are:
• the Celsius scale with the unit symbol °C (formerly called centigrade)
• the Fahrenheit scale (°F)
• the Kelvin scale (K), the latter being used predominantly for scientific purposes. The
kelvin is one of the seven base units in the International System of Units (SI).
-----Raising the temperature of gas increases the pressure, if the volume is held
constant.( temp and pres. Are directly proportional.

6. •Volume (symbol: V) - is the amount of space that a substance or
object occupies, or that is enclosed within a container
• The SI unit of volume is the cubic meter (m3), which is a derived unit.
• Liter (L) is a special name for the cubic decimeter (dm3). The symbol for the liter is (L)
• Milliliter (mL) is a special name for the cubic centimeter (cm3).
-----in a smaller container, the molecules have less room to move.
----- as the volume decreases, pressure increases( syringe)
----- thus, volume and pressure are inversely proportional to each other

7. •Amount in Moles (n) -The mole
is the amount of substance containing the same number of molecules
• The mole, symbol mol, is the SI unit of amount of substance.
• ---- When we inflate balloon, we are adding gas molecules.
• ----Increasing the numbers of gas particles increases the number of collisions
• ---- the pressure increases, if the amount of gas particles increases.

8. >>>THE GAS LAW<<<
1. Boyle’s Law- ( Robert Boyle 1627-1691)
Gas pressure is inversely proportional to the volume, when temperature is
held constant.
Equation : P1 V1 = P2 V2 = P1 =P2XV2/V1

9. EX.
1. A balloon contains 7.2L of He. The pressure is reduced to 2.00 atm and the balloon
expands to occupy a volume of 25.1L . What was the initial pressure exerted on
the balloon?

10. 2. Charles’s Law (Jacques Charles 1746-1823)
The volume of fixed mass of gas is directly proportional to the Kelvin
temperature, when pressure is held constant.
V1/T1 =V2/T2 thus, the P is constant
Temperature must be in kelvin. 0=C is equal to 273 k
V2= T2xV1/T1

11. EX
1. A balloon is filled with 3.0L of helium at 310 K. The balloon is placed in an oven
where the temperature reaches 340 K. What is the new volume of the balloon?

12. 3. Avogadro’s Law is V/n=k.
V is the volume of the gas, n is the amount of substance of the gas, and k is a
proportionality constant.
V1 / n1 = V2 / n2 or V1n2 = V2n1

13. EX
1. 5.00 L of a gas is known to contain 0.95 mol. If the amount of gas is increased to
1.80 mol, what new volume will result ( at an unchanged temperature and pressure )
?

14. 4. Dalton’s Law
– is particularly useful in calculating the pressure of gases collected over water.
P total = P1 + P2 + P3 . . .

15. 5. Graham’s Law
Diffusion and effusion
Diffusion - molecules moving from areas of high concentration to concentration.
ex. Perfume molecules spreading across the room.
Effusion - Gas escaping through a tiny hole in a container.
>>>both depends on molar mass of the particle which determine the
speed.

16. QUIZ