View
30
Download
0
Category
Tags:
Preview:
DESCRIPTION
Chapter 16 Section 3. Gas Behavior. Pressure!. Definition of pressure is: Amount of force exerted on an area P = F/A Unit in SI: Pascal (Pa) One Pascal is one Newton force on an area 1 square meter Gases exert pressure due to KE of their particles. Boyle’s Law. Robert Boyle (1627-1691) - PowerPoint PPT Presentation
Citation preview
Chapter 16 Section 3
Pressure!
Definition of pressure is:Amount of force exerted on an areaP = F/AUnit in SI: Pascal (Pa)One Pascal is one Newton force on an area
1 square meter
Gases exert pressure due to KE of their particles
Boyle’s Law Robert Boyle (1627-1691) Studied relationship between volume
and pressure of gases Found: as volume goes up, pressure
goes downProduct of pressure and volume of a gas is
a constant if temperature does not change As an equation: PV=constant http://www.grc.nasa.gov/WWW/K-12/airplane/Animation/
frglab.html
Boyle’s Law
More commonly, we compare pressure and volume of the same gas
Since PV is constant, we can say:P1V1 = P2V2 for any gas
To see this in action, let’s do Math Skills Activity p 505!
Math Skills Activity!
A balloon has a volume of 10.0 L at a pressure of 101 kPa. What will the balloon’s new volume be if the pressure changes to 43 kPa?
What we know:P1 = 101 kPa
V1 = 10.0 L
P2 = 43 kPa
V2 = ?
What equation?P1V1 = P2V2
So V2 = P1V1
P2
Put in the values!V2 = (101 kPa)(10.0L)
(43 kPa) Do the math!
V2 = 23.488 L Check units and math!
Another Problem:
A volume of helium occupies 11.0 L at 98.0 kPa. What is the new volume if the pressure increases to 101.0 kPa?
What do we know?P1 = 98.0 kPa
V1 = 11.0 L
P2 = 101.0 kPa
V2 = ?
What equation?P1V1 = P2V2
So V2 = P1V1
P2
Put in the numbers!V2 = (98.0 kPa)(11.0 L)
(101.0 kPa)
Do the math!V2 = 10.67 L
Check your math and units.
Charles’ Law Jaques Charles (1746-1823) Studied relationship of temperature and
volume with constant pressure As temperature goes up, volume
increases Volume/Temperature is a constant As an equation: K = V/T This relationship is the basis for the
Kelvin temperature scale
Charles’ Law
More commonly, we compare one situation to another for a gas
V1 = V2 With constant pressure
T1 T2
Temperatures must be used in Kelvins!
Charles’ Law Problem
If a balloon has a volume of 2.0 L at 25oC, what is the volume of the balloon at 3oC?
What do we know?T1 = 25oC = 298 K
V1 = 2.0 L
T2 = 3oC = 276 K
V2 = ?
Charles’ Law Problem What equation?
V1 = V2
T1 T2
So V2 = V1T2
T1
Put in the numbers! Remember, temperature must be in Kelvins!V2 = (2.0L)(276 K)
(298 K) Solve!
V2 = 1.85 L Check for math and units.
Earth’s Atmosphere
Earth’s atmosphere divided into 5 layers
Earth’s Atmosphere
Exosphere: outer layer Thermosphere Mesosphere Stratosphere Troposphere: layer we live in!
Exosphere
Very thin outer portion of atmosphere Negligible pressure
Thermosphere Extends from about 90 km to about 500 km
above Earth Very low pressure Very high temperatures (1000oC) in upper
regions Gases here broken into atoms by energy
from sun Much of X-ray and UV radiation absorbed
here Aurora occurs in this layer
Mesosphere
About 50 to 85 km above Earth’s surface
Temperatures get very cold (-25oC to -90oC)
Air is mixed by currents Most meteors burn up in this layer
Stratosphere
Altitude of the bottom of this layer varies with latitude and season16 km at equator8 km at poles
Ozone heats this layer as it absorbs UV from sun
Very few clouds, very dry air
Troposphere
Layer we live in! From surface up to 7 to 20 km altitude Almost all weather occurs in this layer Almost all dust particles and water vapor
in this layer This layer heated from below, so
warmer at lower altitudes than higher
Gases are fun!
Recommended