Kinetic Theory - The Gaseous State

Over the last two lessons we have seen that liquids and solids are made out of moving particles. In this lesson we find out that gases are made out of the same particles. The main difference between the particles in a gas and the other two states is that the gas molecules move around much more.

Gases

If you look at the diagram of gas particles you see that they move around much more than for those in solids or liquids. You might also notice that the distances between the particles in a gas are bigger than in the other two states: in other words the particles in a solid are closest together; and in a gas the particles are furthest apart.

The particles in a gas are able to flow. They also move all around the container - bouncing off the top, bottom and side walls in equal numbers. It is this bouncing off the walls that causes a gas to exert pressure (like the pressure exerted by the bubbles of gas in a can of lemonade).

gas particles move about much more than liquids and solids

 

Now answer these questions ...

  1. All gases are made out of what ?
  2. Are gas particles moving or still ?
  3. Do the gas particles move more or less than in a liquid ?
  4. Do the gas particles move more or less than in a solid ?
  5. Is there a bigger or smaller distance between gas particles compared with liquid ones ?
  6. Which particles are the closest together: solid, liquid or gas ?
  7. Which particles have the most energy: solid, liquid or gas ?
  8. Does a gas take up the shape of a container, yes or no ?
  9. Can a gas flow, yes or no ?
  10. When gas particles bounce off walls they exert what ?

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Energy

A particle needs energy to move around. The more a particle moves around the more energy it needs. Because gas particles move around the most - they have the most energy.

When you boil the water in a kettle you start to see the steam coming out of the spout. A number of steps cause this to happen:

  • the kettle gives the water particles heat energy
  • the heat energy changes to movement (or kinetic) energy
  • the water particles move around more
  • the distances between the particles increases
  • soon the particles have enough energy to turn into a gas
  • the steam is able to leave the container (kettle) by the spout - this stops the pressure from getting too high

If, on the other hand, you put the kettle of water into the freezer the energy of the water particles would travel out of the kettle. With less energy, the particles would move around less and would get closer together.
The water would turn solid - into ice.

... and now these questions

  1. What do particles need to make them move ?
  2. What type of energy is movement energy ?
  3. To make a particle move more do you give it more or less energy ?
  4. What type of energy could you give water to turn it to steam ?
  5. When a liquid is heated does the distance between the particles increase or decrease ?
  6. If the particles have enough energy do they turn into a solid or a gas ?
  7. If the particles lose energy do they turn into a solid or a gas ?
  8. Does the steam take up the shape of the container, yes or no ?
  9. Is the steam able to leave the container, yes or no ?
  10. If the steam couldn't escape - what would increase ?

You scored out of 10 on that test