States of Matter & Gases

States of Matter The three states of matter include: Solid: Liquid: Gas State Volume Shape Solid definite Liquid indefinite Gas

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: 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 °C = K – 273 You try: 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: P1V1= P2V2 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: V2 = P1V1 T2 T1 P2 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: PV = nRT Includes the amount of a gas in moles (n) 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