Energy and States of Matter

Energy

•When particles collide, energy is transferred from one particle to another.

•Law of conservation of energy: energy can be neither created nor destroyed; it can only be converted from one form to the other.

Energy

•Kinetic energy – energy of motion•Potential energy – the energy stored relative to a

particle’s position

•Metric unit for measuring kinetic and potential energy is Joules (J)

Temperature

•measure of the average kinetic energy of all particles in a substance

•Substances at the same temperature have the same average kinetic energy.

Temperature

• Kelvin scale: based on absolute zero

• absolute zero • zero on Kelvin scale• written as 0 K• Defined as the temperature at

which all particle motion stops

• No negative Kelvin temps

• For all gas law problems, the temp must be in Kelvin

Temperature

K = C° + 273Convert the following temperatures into Kelvin:a. 43 oCb. –135 0C

Convert the following temperatures into Celsius:a. 340 Kb. 30 K

Pressure

•Force per unit area•Pressure of a gas is due to the collisions of particles with the sides of the container in which it is enclosed

Which has more pressure? Why?

A B

Pressure

The metric unit for measuring pressure is ATMOSPHERE (atm).

Other units for measuring pressure:• 1 atm = 760 mm Hg = 101.3 kPa

Atmospheric Pressure decreases with increasing altitude.

(hendrix2.uoregon.edu)

1 atmosphere is defined as the air pressure at sea level.

STPStandard Temperature and

Pressure

Standard temperature = 0°C

Standard pressure = 1 atm

Particle Diagram

http://www.patana.ac.th/secondary/science/anrophysics/unit5/commentary.htm

Solid Liquid Gas

Motion/Kinetic Energy of Particles

Force of Attraction for the Same Substance

PhET Simulation

• PhET Simulation

Solids

• Physical properties used to describe solids:

•Hardness•Shape•Malleable•Ductile•Density•Elasticity

• Characteristics of solids:• Particles are very close

together• Strong attractive forces

between particles• Particles vibrate but do

not move out of position• Fixed shape• Fixed volume

Liquids

• Physical properties used to describe liquids:

•Viscosity (resistance to flow)•Concentration•Fluid (has the ability to flow)•Density

• Characteristics of liquids:▫Particles are close together▫Weak attractive forces between particles▫Particles slide past each other▫Takes the shape of the container▫Fixed volume▫Compressible (move particles closer together by applying a force)

Gases▫ Particles are far apart▫ No attractive forces between particles▫ Takes the shape of the container▫ Particles spread out to fill the container▫ Can be identified by “burning splint” test:

O2 gas causes the burning splint to re-light CO2 gas causes the burning splint to go out quietly (fire

extinguisher) H2 gas causes a popping sound

Gases as Diatomic Molecules There are seven

elements (all gasses) whose atoms are not stable as individuals, so they always bond with another atom.

If no other type of atom is available, they bond with another atom of the same type and form DIATOMIC MOLECULES.

H2, O2, F2, Br2, I2, N2, Cl2

Common Gases

http://patti-isaacs.com/portfolio/

Air is a mixture of gases:

Nitrogen (N2)

Oxygen (O2)

Argon (Ar)

Carbon dioxide (CO2)

Hydrogen (H2)

Ammonia (NH3)

Methane (CH4)

Kinetic Molecular Theory

1. Gases consist of tiny particles (atoms or molecules).

2. These particles are so small, compared with the distances between them that the volume (size) of the individual particles can be assumed to be negligible (zero).

3. The particles are in constant random motion, colliding with the walls of the container. These collisions with the walls cause the pressure exerted by the gas.

4. The particles are assumed to not attract nor repel each other.

5. The average kinetic energy of the gas particles is directly proportional to the Kelvin temperature of the gas.

Direct relationship

•changing one variable causes the other variable to change in the same direction

Inverse relationship

Inverse (indirect) Relationship

•changing one variable causes the other variable to change in the opposite direction

Gas laws

Relate the variables:•Volume•Pressure•Temperature•Number of particles (…number of moles)

•Independent variable – the variable that you control

•Dependent variable – also called “responsive” variable because it changes in response to the independent variable

•Example: The number of hours worked relates to the amount of money earned.• Independent variable: # of hours worked•Dependent variable: $ earned•This shows a direct relationship

Boyle’s law

Demo – marshmallows and vacuum pump• Independent variable:_______________________•Dependent variable: ________________________•Observations: ____________________________________________________________________________________• Relationship: ______________________________

Boyle’s Law•gas pressure is inversely proportional to volume at

constant temperature and number of particles of gases.

▫Mathematical relationship:

P1V1 = P2V2

Boyle’s Law

A was balloon inflated in San Diego, CA and then taken to Denver, CO

(www.faculty.sdmiramar.edu) 

Boyle’s law

Boyle’s Law Guided Practice:

•A gas has a volume of 100 ml when the pressure is 1.4 atm.

What is the volume, in mL, when the pressure is increased to 1.6 atm and the temperature is held constant?

If a gas has a volume of 100 ml when the pressure is 1.4 atm, what is the volume, in mL, when the pressure is increased to 1.6 atm and the temperature is held constant?List variables:▫V1 = 100 mL▫P1 = 1.4 atm▫V2 = ? mL▫P2 = 1.6 atm

Write formula:▫ P1V1 = P2V2

Substitute in known values:▫ (100mL)(1.4atm) = (V2)(1.6atm)

Rewrite without units.• (100)(1.4) = (V2)(1.6)• If desired, switch the sides…

(V2)(1.6) = (100)(1.4) • If desired, switch the unknown and number…

(1.6)(V2) = (100)(1.4)

Solve for unknown:▫ Combine terms

(1.6)(V2) = 140 ▫ Isolate the variable▫ (1.6)(V2) = 140 1.6 1.6

▫ V2 = 87.5 mL

Very Important:Check to see if your answer makes sense…pressure increased by a little (1.4 to 1.6) so volume should decrease by a little (100 to 87.5).

Boyle’s Law Guided Practice:

The volume of a quantity of a gas held at constant temperature and 1.00 atm of pressure is 100. mL. What pressure does it take to reduce the volume to 85 mL?

Charles’ law

•Demo – balloons• Independent variable:_______________________•Dependent variable: ________________________•Observations: ______________________________________________________________________________________________________________________• Relationship: ______________________________

Charles’ Law

•The volume of a given amount of gas varies directly to its kelvin temperature when pressure is constant.•Mathematical relationship:V1 = V2

T1 T2

Charles’ Law

cfbt-us.com

Charles’ Law guided practice

• A balloon inflated in an air conditioned room at 27◦C has a volume of 4.00 L. If it is heated to 57◦C and the pressure remains constant, what is the new volume?

A balloon inflated in an air conditioned room at 27◦C has a volume of 4.00 L. If it is heated to 57◦C and the pressure remains constant, what is the new volume?

List variables andConvert temp to Kelvin:▫T1= 27°C + 273 =

300 K▫V1 = 4.00 L▫T2 = 57°C + 273 =

330 K▫V2 = ? L

Write formula:▫ V1 = V2

T1 T2

Substitute in known values:(4.00L) = (V2)_(300K) (330K)

Rewrite without units▫ (4.00) = (V2)_ (300) (330)

Cross multiply…

(4.00)(330) = (300)(V2)Combine terms…

1320 = (300)(V2)If desired, switch sides…

(300)(V2) = 1320Isolate variable…

(300)(V2) = 1320 300 300

Solve for unknown :V2 = 4.4 L

Check to see if your answer makes sense…•temp went up by 10%, •volume went up by 10%.

Charles’ law guided practice:

A gas kept at constant pressure has a volume of 10.0 L at 25.0°C. At what Celsius temperature would the gas have a volume of 20.0 L?

Gay-Lussac’s law

•Demo – crush the can• Independent variable:_______________________•Dependent variable: ________________________•Observations: ______________________________________________________________________________________________________________________• Relationship: ______________________________

Gay Lussacs Law

• The pressure of a gas varies directly to the Kelvin temperature of the sample, if the volume remains constant.

▫ Mathematical relationship

P1 = P2

T1 T2

Gay-Lussac’s law

Gay Lussac’s Law

cfbt-us.com

Graph of Gay-Lussac’s Law(direct relationship)

Gay-Lussac’s Law guided practice

• A gas in an aerosol can is at a pressure of 1.00 atm and 27.0 oC. If the can is thrown into a fire, what is the internal pressure of the gas when the temperature reaches 927 oC?

A gas in an aerosol can is at a pressure of 1.00 atm and 27.0 oC. If the can is thrown into a fire, what is the internal pressure of the gas when the temperature reaches 927 oC?

• List variables • Convert temp to Kelvin:

• P1 = 1.00 atm• T1= 27°C + 273 = 300 K• P2 = ? atm• T2 = 927°C + 273 = 1200 K

• Write formula:▫ P1 = P2

T1 T2• Substitute in known values: ▫ (1.00atm) = (P2) (300K) (1200K)• Rewrite without units…(1.00) = (P2) (300) (1200)• Cross-multiply…(1.00)(1200) = (300)(P2)• Combine terms…1200 = (300)(P2)• If desired, switch sides…(300)(P2) = 1200• Isolate variable…(300)(P2) = 1200 300 300

• Solve for unknown:▫ P2 = 4.00 atm

• Check to see if your answer makes sense…temp quadrupled, pressure quadrupled.

Gay- Lussac’s law guided practice:

A sample of a gas has a pressure of 1.13 atm at 285°C. To what Celsius temperature must the gas be heated to double its pressure if there is no change in the volume of the gas?

Real-world application

• Car tire pressure should be measured when the tires are warm after it has been driven. Why?

http://www.racintoday.com/archives/39412

Real-world application

• This tanker was steam cleaned on the inside, then closed. Why did it implode?

http://jmfs1.ortn.edu/myschool/DHundermark/jms8bscience/index_testpage.html

Real-world application

• Why do aerosol cans have a warning to not incinerate them (put them in fire)?

http://www.sunlive.co.nz/news/26907-explosion-and-fire-warning.html

IDEAL VS. REAL GASES

•Ideal gases don’t actually exist, but many gases do behave ideally under certain conditions (far apart and not able to attract each other).

•Ideal behavior occurs when thePressure is ______________Temperature is __________Mass is ___________Volume is ____________

1. Which gas would act more ideally?

a) He(g)b) H2O(g)

2. Does helium act more ideally at:a) 800Kb) 80K

3. Does helium act more ideally at: a) 20.0 atmb) 1.00 atm

Ideal Gas Law

• relates • Pressure • Volume• Temperature• number of moles(n)

• For a gas at STP, moles(n) and volume (v) are DIRECTLY related.• 1 mole = 22.4 L at STP• This is called “molar volume”

We haven’t used this

variable yet!

READ ONLY, DO NOT COPY!!!!!!• For any ideal gas, the ratio VP is constant. nT

• We call this ratio R, the ideal gas constant.

• Using standard temp and pressure conditions, we can calculate the value of R.

• R = (22.4L)(1atm) (1mol)(273K)

• R = 0.0821 L atm/mole K

• Since R is a constant, we will never be solving for it. RearrangeR = VP

nT to PV = nRT

PV = nRT (pronounced “pivnert”) is called the ideal gas law equation

Ideal Gas Law guided practice

• What volume would 1.41 moles of oxygen occupy at 351K and 2.30 atm?

What volume would 1.41 moles of oxygen occupy at 351K and 2.30 atm?

List variables Convert temp to Kelvin:▫V = ?▫n = 1.41 moles▫T = 351 K▫P = 2.30 atm▫R = 0.0821 L

atm/mol K

Write formula:• PV = nRT

Substitute in known values:(2.30atm)(V) = (1.41mol)(0.0821Latm/molK)(351K)

Rewrite with no units…(2.30)(V) = (1.41)(0.0821)(351)Combine terms…

Solve for unknown: Combine variables, then divide to get v by itself.• V = 17.7 L

Ideal gas law practice:

What temperature, in Celsius, would 6.00 moles of Helium occupy in a 25.0 L container at 1.26 atm?

Independent Practice (10 min)

1. Calculate the pressure (in atm) of a 212 Liter tank containing 23.3 mol of argon gas at 25°C?

2. At what temperature would 2.10 moles of N2 gas have a pressure

of 1.25 atm and in a 25.0 L tank?

3. What volume is occupied by 5.03 g of He at 28°C and a pressure of 0.998atm?

4. A 5000. L weather balloon contains 10.0 moles of He gas. What is the pressure (in atm) when the balloon rises to a point where the temperature is -10.0°C and the gas has completely filled the balloon.

Avogadro’s Principle

Equal volumes of gases at the same temperature and pressure contain the same number of molecules.

Volume and number of particles are directly related.*** The type of gas doesn’t matter.***

V1 = V2

n1 n2

Avogadro’s LawAt STP, one mole of a gas occupies a volume of 22.4 L.

1.0 mol of gasor

6.02 x 1023 particles

22.4 L container

Which container has the most gas particles?

2 L1 atm

3 L0.5 atm

5 L0.20 atm

All containers are at the same temperature.

AB

C