1. Unit 8 - Gases
Chapter 13.1 and
Chapter 14

2. Measurements with gases
Pressure – pressure is simply a measure of how frequently, and how hard, particles collide with their container.
Units for pressure include:
* atmospheres (standard pressure = 1 atm)
* kilopascals (standard pressure = kPa)
* millimeters of Hg (standard pressure = 760 mmHg)
* torr (standard pressure = 760 torr)
Use the standard values to convert from one unit to the other.
1 atm = kPa = 760 mmHg = 760 torr

3. Conversion example A gas is found to have a pressure of 99.2 kPa.
1. What is this pressure in atm?
2. What is this pressure in mmHg?

4. Measurements with gases
Volume – measure of how much space is taken up.
Gas particles are spread far apart.
Between the particles, there is empty space.
The volume occupied by a gas includes the entire volume occupied by the particles and the empty space between the particles.

5. Measurements with gases
Temperature – temperature is the measure of average kinetic energy. As particles move faster, the temperature increases.
Units for temperature include:
* Celsius (standard temperature = 0°C)
* Kelvin (standard temperature = 273 K)

6. Temperature K = ºC + 273 ºC -273 100 K 273 373
Always use absolute temperature (Kelvin) when working with gases. ºC
-273
100 K
273
373
K = ºC + 273

7. Characteristics of Gases
Gases expand to fill any container.
random motion, no attraction
Gases are fluids (like liquids).
no attraction
Gases have very low densities.
lots of empty space

8. Characteristics of Gases
Gases can be compressed.
no volume = lots of empty space
Gases undergo diffusion & effusion.
random motion