States of Matter
&
Gases
States of Matter
The three states of matter include:
Solid: Liquid: Gas
State
Volume
Shape
Solid
definite
definite
Liquid
definite
indefinite
Gas
indefinite
indefinite
Energy and phase change
• When Heated:
Solid  liquid  gas
• When Cooled:
Gas  liquid  solids
Energy & phase change
Heating Curve & phase changes
• Substances can exist in three states. They are solid, liquid, and gas. They
(the substances) change when the kinetic energy of a substance changes.
• When a substance changes from a solid to a liquid, it is called melting.
• When a substance changes from a liquid to a gas, it is called vaporization.
• Gas particles have the most kinetic energy of the three states, but they
also have the lowest potential energy. This is opposite of a solid which
has high potential energy but low kinetic energy.
• There is one special phase change which is not common. The change is
from a solid to a gas. This is called sublimation.
Heating Curve of Water:
100° C -Temperature
0° C --
Energy added 
Heating Curve of Water
Each plateau represents a physical change .
The energy that is added is used to change the state of water.
Each slope represents the increase in temperature.
The energy that is added is used to heat the of water.
Gases:
• Parameters used to describe Gases:
• The variables used to describe the properties of a gas include:
•
•
•
•
P = Pressure
V = Volume
T= Temperature
n = moles (amount)
Temperature:
• Temperature (T): must be described using the unit Kelvin (K).
K = °C + 273
• You try:
°C = K – 273
1. 25 °C = _______ K
298 K
2. 450K = _________ °C
177 °C
Pressure:
• Pressure (P): measures the force/area in units of atm., mm Hg or kPa
1 atm = 760 mm Hg = 101.3 kPa
Now you try!
1. Convert 0.95 atm to mm Hg
722 mmHg
2. Convert 0.95 atm to kPa
96.2 mmHg
3. Convert 100.5 kPa to mmHg
754 mmHg
Volume:
• Volume (V): is defined using milliliters (mL) or liters (L)
1000 mL = 1L
Now you try!
1. 150 mL = _________ L
.150L
2. 34.5 L = __________ mL
34,500 mL
Atmospheric Pressure:
• Atmospheric pressure: is the pressure exerted by the weight of air in the
atmosphere. Traditionally it is measure using a barometer.
• https://www.youtube.com/watch?v=jmQ8FWnM0fA
Does atmospheric pressure really exist?
Collapsing Can experiment:
• Objective- to prove that atmospheric pressure exists.
Fill in the remaining part of this experiment together in class:
• Background to experiment:
• Observations:
• Interpretation of findings:
• https://www.youtube.com/watch?v=JsoE4F2Pb20
Gas Laws:
• Boyle’s Law
Describes the inverse (  )relationship of pressure: volume
P1V1= P2V2
Sample calculation: Boyle’s Law
• A gas has an initial pressure of 1.0 atm and a volume of 1.5L. What is
the new volume when the pressure is increased to 1.2 atm?
P1 = 1.0atm
V1 = 1.5L
P2= 1.2 atm
V2= ?
Answer: V2= 1.25L
Gas Laws:
• Charle’s Law
Describes the direct relationship between temperature and volume ( ).
V1 = V2
T1 T2
Remember: Temperature is defined by Kelvin (K = °C + 273)
Sample calculation: Charles's Law
• A gas has an initial temperature of 275K and a volume of 0.45L. What
is the new volume when the temperature is increased to 300K?
•
•
•
•
V1 = 0.45L
T1 = 275K
T2 = 300K
V2 = ?
Answer : 0.49L
The combined gas law
• The combined gas law pulls together the inverse relationship of P:V
and the direct relationship of V:T
• The combined gas law:
Combined gas law:
P1= 1.5 atm
V1 = 0.75L
T1 = 276K
P2 = ?
V2 = 1.25L
T2 = 295K
V2 = P1V1 T2
T1 P2
Answer = 0.96 atm
The Ideal Gas Law:
• Includes the amount of a gas in moles (n)
PV = nRT
P= pressure (atm)
V= volume (L)
n = moles
R = gas constant: 0.08206 L atm/ mole K
T = temperature (K)
Practice problem:
• Calculate the pressure of 0.500 moles nitrogen gas in a 10.0L
container, held at 298K.
P= ?
V = 10.0L
n = 0.500 mole
T = 298K
R = 0.08206 L atm/mole K
P = nRT
V
Answer = 1.22 atm
Gas law applications:
Mountaineering
Scuba Diving
Hot Air balloons
Tire pressure