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:

Energy added

Temperature

0° C --

100° C --

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 °C = K – 273

• You try: 1. 25 °C = _______ K298 K

2. 450K = _________ °C177 °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 Hg722 mmHg

2. Convert 0.95 atm to kPa96.2 mmHg

3. Convert 100.5 kPa to mmHg754 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 = __________ mL34,500 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 LawDescribes 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 P2 = ?

V1 = 0.75L V2 = 1.25L

T1 = 276K 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 = molesR = gas constant: 0.08206 L atm/ mole KT = temperature (K)

Practice problem:• Calculate the pressure of 0.500 moles nitrogen gas in a 10.0L

container, held at 298K.

P= ?V = 10.0Ln = 0.500 moleT = 298KR = 0.08206 L atm/mole K

P = nRT V

Answer = 1.22 atm

Gas law applications:

Mountaineering Scuba Diving

Hot Air balloons Tire pressure