5E gas law lesson.pptx

INTRODUCTION

TO GAS LAWS

Bell Work (1/23/12)

You are about to venture out on a SCUBA

diving expedition, but first you need to brush up on your knowledge of the gas laws.

1) Summarize what you know about gases.

2) How do you think changing the temperature

of a gas affects its behavior.

3) How do you think changing the volume or

space that a gas occupies will affect the behavior of gas particles?

Objectives

 You will explore the relationships between

pressure, volume, and temperature

 You will be able to create graphs of the different

relationships based on your observations

 You will be able to predict the outcome of a given

scenario by applying your knowledge from your graphs and observations

Kinetic Theory

 Kinetic: “Moving/motion”

 Recall: All matter is made of tiny

particles that are in constant motion.

○ _{Solids- motion is vibration}

○ _{Liquids- particles are free to move around} ○ _{Gas- very fast and move in straight line}

Kinetic Theory



The average kinetic energy of

molecules is the temperature of the

substance

 _{The faster the molecules move, the}

higher the temperature and the slower the molecules the lower the temperature.

Properties of Gases

 Expansion

 _{Gases expand to fill any size container}

 Pressure

 _{Gases exert pressure}

 _{Pressure is collisions with a container}

 Density

 _{Low density}

 _{Density of gases is much lower than}

densities of solids and liquids

Properties of Gases

 Compressible

 _{Gases are compressible, meaning that a}

certain amount of gas can be compressed into a smaller volume

 Diffusion

 _{Diffusion is the mixing of 2 or more gases}

due to collisions of molecules

 _{Particles move from a region of higher to}

Pre-simulation

Make predictions of what the following graphs would look like:

Volume (y) to Pressure (x)

Volume (y) to Temperature (x) Pressure (y) to Temperature (x)

Simulation

Verify Predictions

 Verify whether or not your predictions are

correct and make any necessary changes.

 Write in your own words the relationship that

exists between pressure and volume.

 Write in your own words the relationship that

exists between temperature and volume.

 Write in your own words the relationship that

Using your knowledge

Why should a diver not hold his/her breath underwater when ascending to an area of lesser water pressure?

Before you go

 Explain why a bicycle tire looks more

inflated during the summer than winter.

 A container is filled with gas and placed

in ice. What will happen to the pressure of the gas? What about the volume of the gas?

Boyle’s Law

Named for Robert Boyle

 If temperature and amount of gas particles

remain constant, then pressure and volume are inversely proportional

 _{Inversely proportional: when one increases the}

other decreases

P1V1 = k

P2V2 = k

Therefore: P

V

=

P

V

Unit of volume = liters (L)

Unit of pressure is: mmHg, torr, atm, or Pascals (P)

Units of Pressure

1atm =

760 mmHg

760 torr

101.325 kPa

Standard pressure- the pressure of the air at

sea level (760mmHg, or 1 atm, or 101.3kPa)

Barometer

Pressure

=

Force

Area

Make the following Conversion

factors

Atm to torr kPa to atm

mmHg to atm kPa to mmHg atm to mmHg

Try these…

Convert:

1.727 mmHg into kPa

727mmHg x 101.325kPa 760mmHg

2.52.5 kPa into atm

3.0.729 atm into mmHg 4.522 torr into kPa

5.800.0 mmHg into atm 6.495Pa into mmHg

Examples of Boyle Law at

work

A syringe being used to draw blood

Popping a balloon

Popping ears during

elevation change

A sample of chlorine gas occupies a volume

of

946mL

at a pressure of

726mmHg

. What

is the pressure of the gas (in mmHg) if the

volume is reduced at constant temperature

to

154 mL

?

A sample of chlorine gas occupies a volume of

946mL at a pressure of 726mmHg. What is the pressure of the gas (in mmHg) if the volume is reduced at constant temperature to 154 mL?

P

x

V

=

P

x

V

P

= 726 mmHg

V

= 946 mL

P

= ?

V

= 154 mL

P

P

x

V

V

= 726 mmHg x 946 mL

_{154 mL}

Charles’ Law

 Name for Jacques Charles

 If pressure and the amount of gas remain

constant, then Kelvin temperature and the volume of gas are directly proportional

 _{Directly proportional: as one increases so does}

the other. As one decreases so does the other.

V₁/T₁ = k

Why is the Kelvin scale used

exclusively in gas law calculations?

To convert

C



K

T

(K) =

t

(

C) + 273

All temperature must be converted to

Kelvin

Because there are no negative temperature

To convert K



C

A sample of carbon monoxide gas

occupies 3.20 L at 125

C. At what

temperature will the gas occupy a volume

of 1.54 L if the pressure remains constant?

A sample of carbon monoxide gas occupies 3.20 L at 125 0C. At what temperature will the gas occupy a

volume of 1.54 L if the pressure remains constant?

V

= 3.20 L

T

= 398 K

V

= 1.54 L

T

= ?

T

=

V

x

T

V

1.54 L x 398 K

_{3.20 L}

= 192 K

Practice

If a paint ball CO

tank

is at a

pressure of

2000ps

i

and you

know that

1psi

equals

51.7mmHg

, how

many

atm

of pressure

are in the tank?

Boyles law:

P

x

V

=

P

x

V

Charles law:

V

/

T

=

V

/

T

P

V

= P

V

T

T

A balloon is filled with hydrogen gas to a

volume of

0.5L

, and a pressure of

2.0atm

at a temperature of

25°C

. If the balloon is

then left out in the sun at a temperature of

35°C

and reaches a new volume of

2.0L

,

what is the new pressure?

Demo Time?!



Recall: What are the products when

zinc metal reacts with hydrochloric

acid (HCl)?