particles in gases

• Particle motion


  Particles in a gas are moving very quickly in random directions. The speeds of the particles vary but, on average, they move quicker than they do in liquids and solids. This means that it does not take long for a gas to spread out to fill its entire container.
• Gas pressure


  The collisions caused by a gas trapped inside a container cause forces to act outwards in all directions, giving the container its shape.
• Calculating gas pressure


  pressure = force / area
• The pressure in the atmosphere (atmospheric pressure) at sea level is about 100,000 N/m2
• The pressure from gas molecules may increase


  If there are more molecules colliding each second or if the molecules are moving faster
• Volume


  A measure of the amount of space or capacity a three-dimensional shape occupies
• An average can of fizzy drink has a volume of 330 ml
• If the volume of a container with a gas inside stays the same

  The pressure of the gas increases as its temperature increases
• Temperature


  A measure of the average kinetic energy of particles in a substance
• The higher the temperature, the higher the average kinetic energy of gas particles
• As gas temperature increases

  The gas particles will be travelling faster and will collide with the walls of the container more frequently, and with more force
• Pressure


  Force exerted over an area
• As temperature increases


  Pressure increases
• Pressure is directly proportional to temperature
• Gas pressure


  Force exerted over an area. The greater the pressure, the greater the force exerted over the same area.
• If pressure is increased

  Volume decreases
• Particle theory


  The scientific theory used to explain the properties of solids, liquids and gases. It involves the arrangement and movement of the particles in a substance.
• Inversely proportional


  A relationship between two variables where as one variable increases, the other variable decreases, eg as the volume doubled, the pressure decreased by half.
• Boyle's experiment


  1. Pouring mercury into a J-shaped tube that was sealed at one end to trap a bubble of air

  2. Observing that the higher the column of mercury, the greater the pressure the trapped air was experiencing and the smaller the bubble became
• Boyle was able to show that volume is inversely proportional to pressure
• Pressure x Volume = constant


  For a fixed mass of gas at a constant temperature
• If temperature of a gas stays the same

  Pressure increases as volume decreases
• Gases


  Take up more space than solids or liquids and their particles are moving much faster
• Temperature, pressure and volume of gases


  • Are all related
• Gases contain particles that are moving around
• Forces applied to the particles in a gas

  Result in a transfer of energy
• Mechanical work


  Transfers energy from the person or machine's store of chemical energy to the internal energy store of the gas
• Volume of the gas decreases


  Pressure increases because the particles are moving in less space and collide more often
• Increased pressure leads to an increase in temperature


  Because the temperature is a measure of the average kinetic energy of particles - the increase in the internal energy of the gas (as kinetic energy of the particles) means that the temperature must increase
• This process explains why a bicycle pump gets warm when it is used to inflate a tyre