*pressure in gases

• particles in a gas move randomly and collide with the walls of the container (ex: a balloon) this results in the particles exerting a small force on the wall

  
  

  
  

  the more particles the more collisions, and so the force on the walls increases (*as the force is exerted on an area, the force causes pressure!!)

  
  

  therefore the pressure inside the balloon gets bigger as you blow in more air, pushing the walls of the balloon outwards
• Pressure and depth in gases

  as with liquids, the pressure in a gas increases with depth
• Alititude


  is the height above sea level, (most ppl on earth live at low altitude)
• the earths atmosphere (made from gases) extends to a height of abt 400km above sea level

  sea level is there4 where the atmosphere is at its deepest.

  so at sea level, atmospheric pressure is highest.
• The higher you go in the atmosphere, two variables that affect atmospheric pressure change:

  • the number of particles in 1m^3 of air decreases, so the concentration of gas particles decreases

  
  

  • the weight of air abov your current position decreases
• atmospheric pressure at sea level is about 100 000N/m^2

  we aren't aware of the pressure from the atmosphere bc we live in the atmosphere all the time
• Effects of atmospheric pressure

  this can be shown by pumping air out of a metal container as b4 it's pumped out, the pressure inside is equal to the pressure outside.

  
  

  
  

  the pressure inside the container becomes close to 0 when air is pumped out, but the pressure outside doesn't change.

  
  

  
  

  the container is crushed by the pressure of the air outside the container.
• Pressure and temperature in gases

  as the temp of a gas increases, the speed of particles in the gas increases.

  when particles are travelling faster, their collisions exert more force, meaning that increasing temp of gas will increase the pressure of gas
• Pressure and temperature in gases example:

  water and food are placed inside a pressure cooker with a sealed lid.

  when the water boils, the steam cannot escape so the pressure of the gas inside increases as well as the temperature.

  there is a weight on top of the pressure cooker to control the pressure and valves that allow steam to escape, once the required pressure has been reached.