Molecule movement in a gas
Constant, random motion
What does the temperature of gas dependent on
kinetic energy of its molecules
What happens when you increase the temperature of a gas
The pressure increases because the molecules move faster and collide with the container more frequently. During each collision there is a change of momentum for the molecule which exerts a force on the wall of the container.
What happens if you increase the volume containing a gas whilst keeping it at a constant temperature?
The pressure decreases because whilst the average speed of the molecules remains constant, the distance they have to travel between collision increases, meaning there are fewer collisions per second between the molecules and the container.
How does a bike pump increase the temperature within the wheel
When using a bicycle pump, work must be done to overcome the pressure already in the tyre to push more air molecules in. This work increases the internal energy of the air in the tyre and increases its temperature.
Fluids
gases and liquids (they can flow)
How does upthrust work in a fluid
A partially (or totally) submerged object experiences a greater pressure on the bottom surface than on the top surface. This creates a resultant force upwards. This force is called the upthrust.
Why does the atmosphere get less dense higher up
Air molecules colliding with a surface create atmospheric pressure.
The number of air molecules (and so the weight of air) above a surface decreases as the height of the surface above ground level increases.
So as height increases there is always less air above a surface than there is at a lower height. So atmospheric pressure decreases with an increase in height.
