P1.3 Flashcards
Pressure formula
p = 𝐅/𝐀
Pressure - Pa (pascals)
Why do gases exert a pressure
Particles of a substance in the gas state, move about at high speed, in random directions.
The particles collide with each other,and with the walls of the container.
A gas exerts a pressure, due to the force with which particles collide with the container walls, over a given surface area.
Temperature and gas pressure
The higher the temp, the greater KE, the particles collide more often and with a greater force with walls - greater pressure
Relationship between gas pressure and temperature
There is a directly proportional relationship between temp and pressure, at a constant volume
Relationship between pressure and volume
Pressure and volume are inversely proportional at a constant temp
(Volume doubles = pressure halves)
Why is there an inversely proportional relationship
If you half the volume…
Number of collisions with particles/ container walls doubles
The force exerted per unit time doubles
Pressure of gas doubles
Equation for pressure and volume
pressure (Pa) x volume (m3) = constant
p1 x V1 = p2 x V2
What happens when a gas is compressed
… a force is required to move the gas particles together
… work is done on the gas… gas particles gain kinetic energy… gas particles move faster.
… gas temperature increases.
What happens when a gas expands
… a force is applied by gas particles together
… work is done by the gas… gas particles lose kinetic energy… gas particles move slower.
… gas temperature decreases.
Why do you need to wait before taking a reading of the pressure, after changing the volume
As the volume of the gas was changed, work would have been done on or by the gas.
This would change the temperature of the gas, which would affect the pressure.
Why can earth maintain an atmosphere
Due to its gravitational field
Model of the atmosphere
- made up of a single layer
- the density is the same without
What is the atmospheric pressure
100,000
Atmospheric pressure and altitude
Atmospheric pressure decreases the higher you travel, owing to fewer gas particles, due to a weaker gravitational field.
Why does a balloon expand when it rises
As you travel higher into the Earth’s atmosphere, air pressure decreases.
This is because the Earth’s gravitational field becomes weaker with height, thus fewer gas particles are held onto.
This decrease in pressure outside the balloon, results in a net outward pressure that expands the balloon.
