1. Gas Law Calculations

2. Unit Conversions
Many measurements can have more than one kind of unit.
When making calculations with measurements, it is important that all units for a single variable match.
To match units, in science we must complete unit conversions, converting from one unit to another.

3. Temperature 3 types of units exist to measure Temperature;
Farenheit - only used in the U.S.
Celsius - rest of the world uses
Kelvin - Common in the scientific community
The SI (International) unit for temperature is Celsius and Kelvin.
To convert from Celsius → Kelvin ℃ = K
To convert from Kelvin → Celsius K = ℃
Find the temperature of 98.6 ℃ in Kelvin.

4. Important Temperatures

5. Kelvin Scale
The Kelvin Scale was designed to eliminate negative values for temperature. Thus it is called an “absolute” scale. There are no negative values on the Kelvin scale.
Zero Kelvin (0 K) is known as “Absolute Zero”.
At “Absolute Zero” all molecular motion theoretically stops.
This temperature is “theoretical” and has never actually been achieved.

6. Temperature Conversion Practice
Convert the following temperatures.
1.145 °C = K
2.373 K = °C
3.25 °C = K

7. Volume
The base unit for volume is Liters. A liter is rather large compared with small measurements made in chemistry.
Typically volume is measured in milliliters, mL. This may require a “unit conversion” 1 L = 1000 mL
Another common unit is kiloliters, kL. This requires the conversion 1000 L = 1 kL
Convert the following: a. 65 L = mL b mL = L
c L = kL d. 65 kL = mL

8. Unit Conversion
When converting between units, you need to use math and setup problems so units cancel. That way, you’re left with only the units you want. Follow this step by step procedure when doing gas unit conversions:
1. Figure out what value and units you’re starting with
Conversion value and units of ENDING pressure unit
Starting value and units
2. On bottom, put those same units you started with along with the value for the CONVERSION amount. x
Conversion value and units of STARTING pressure unit
3. On top, put the units you want to convert to along with the value for the CONVERSION amount.

9. Pressure Pressure is measured in a wide variety of units.
On a typical day, at sea level, the atmosphere exerts a force of about 100,000 N on each m2 of your body
This is a pressure of about 100,000 Pascals or 100 kilopascals (kPa).
Units for Pressure:
Standard atmosphere (atm) Millimeters of mercury (mmHg) = torr
Inches of mercury (inHg) Pounds per square inch (psi)
We use the conversions below to convert between units in pressure.
1.000 atm = 101,325 Pa = kPa = mm Hg = torr = in Hg = psi

10. Pressure Unit Conversions
A car tire is commonly measured in psi. Your air gauge only reads in atmospheres (atm). If the maximum pressure marked on the tire is 35 psi, how many atm can be added to the tire?
Given = 35 psi
Unit conversion = 1 atm = psi
35 psi x 1 atm =
14.69 psi
Units must always cancel on top and bottom.
Worth adding a general section about simple unit conversion?
To cancel units:
(Value and unit you start with) x (conversion value and unit you want to end with) / (conversion value and unit you start with) =
Multiply by the stuff on top, and divide by the stuff on bottom.

11. Pressure Conversion Practice
Convert the following using the pressure conversions below:
1.000 atm = 101,325 Pa = kPa = mm Hg = torr = in Hg = psi
754 mmHg = ____ atm = ____ Pa = ____ kPa
6.5 atm = ____ Pa = _____ kPa = _____torr

12. Boyle’s Law
In 1662, a chemist named Robert Boyle investigated gases and discovered the relationship between gas pressure and the volume of a container. In honor of his discovery, it is now named Boyle’s Law.
He discovered that pressure and volume have an inverse relationship.
As volume is decreased, the pressure
of a gas increases (opposite)
As volume is increased, the pressure
of a gas decreases (opposite)

13. Boyle’s Law cont’d Equation for Boyle’s Law: P1 x V1 = P2 x V2
Constants: Temperature and amount of gas present
If a 2 Liter container of gas at 1.5 atmospheres of pressure is condensed to a final volume of 1 liter, what happens to the pressure of the gas inside?
V1 = V2 =
P1 = P2 =