Home » Chemistry » Gas



(Build a table of contents here)

What gases are in our atmosphere?
air pressure
the speed of air molecules
suction doesn’t exist -> really just a difference in air pressure
how do we pull liquids up through a straw?
does hot air really rise? (The balloon rises because the air pushing on the bottom of the balloon has a greater force than the downward force of the air on top of the balloon plus the balloon’s own weight.)


gas laws tutorial


Properties of gases

Kinetic Energy – the energy of particles in motion.

We look at an ideal, monatomic gas.  What do these terms mean?

ideal gas:

monatomic gas:

The temperature of this gas =  average kinetic energy

What is kinetic energy?

Ideal gas assumptions:

* Gas made of very small particles (atoms or molecules.)

* So small, that the total volume of the individual gas molecules, added up, is negligible compared to the volume of the container that they’re in.

* Average distance between particles is large compared to their size.

* Particles all have the same mass.

* In constant, random, and rapid motion.

* They constantly collide among themselves, and with the walls of the container.

* All collisions are elastic.

* Gas molecules are considered to be perfectly spherical

* When not colliding, the particles don’t exert any forces on each other.

The average kinetic energy of the gas particles depends only on the absolute temperature of the system. The kinetic theory has its own definition of temperature, not identical with the thermodynamic definition.
The time during collision of molecule with the container’s wall is negligible as compared to the time between successive collisions.
Because they have mass, the gas molecules will be affected by gravity.

Are real world gases ideal like this?

Not at all. These are simplifying assumptions; they make it much easier to derive mathematical rules for how gases work.

If real world gases are not like this, then why make simplified (“wrong”) assumptions? Why use math formulas that we know are not perfectly correct (“wrong”)?

Answer: These assumptions make the math a hundred times easier, yet the practical, real-world results are almost exactly the same as what we’d get using the more exact assumptions and math.

Under most conditions – including all the weather that you have ever experienced – real world gases behave like ideal gases.

When do these assumptions fail?  Very pressure, or very high temperature.
This Java applet is a simulation that demonstrates the kinetic theory of gases. The color of each molecule indicates the amount of kinetic energy it has


Visualization and Problem Solving for General Chemistry

The triple point

The triple point: Solid, liquid and gas at the same time


Pressure and volume

Atmospheric pressure: How does gravity affect the distribution of gas molecules in the air?

Use this applet:  http://www.falstad.com/gas/  See how changing gravity affects the molecules.

Brownian motion: we see dust particles, or pollen, moving around on still water – why do they move?


The kinetic model of gases: we usually can model gases as an “ideal gas”

What does it mean when something is at absolute zero degrees?


Measuring pressure and temperature

Dalton’s law of partial pressure

Boyle’s law: pressure and volume

PV = c

(borrow these GIFs)



Charles’s law: volume and temperature


Gay-Lussac’s law: pressure and temperature


The combined gas law: pressure, volume and temperature

The ideal gas law: PV = nRT

Graham’s law is about the velocity of particles in a gas / Diffusion


Not all gases have the same density!


Thermal Physics


  1. Lesson 1 – Heat and Temperature
    1. Introduction
    2. Temperature and Thermometers
    3. Thermometers as Speedometers
    4. What is Heat?
    5. Methods of Heat Transfer
    6. Rates of Heat Transfer
  2. Lesson 2 Calorimetry
    1. What Does Heat Do?
    2. Measuring the Quantity of Heat
    3. Calorimeters and Calorimetry


Molecular Workbench: Apps and animations
Physics: Mechanics, Fluid Mechanics and Dynamics, Electromagnetism, Quantum
Chemistry: Thermodynamics, States of Matter, Chemical bonds, Water and solution, Reactions
Biology, Biotechnology, Nanotechnology,



Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: