p1 Flashcards
Relative mass of electron
0.0005
Density doesn’t depend on…
Size or shape
Which varies with state- density or mass
Density as the volume would change
What is specific heat capacity
The change in energy in the substance’s thermal store needed to raise the temp of 1kg of that substance by 1 degrees
What is specific latent heat
Change of energy in its thermal energy store when 1kg of the substance changes state without changing its temp
Why are there flat parts on a heating or cooling curve
The energy is used for breaking bonds to change state instead of raising/lowering the temp
What is specific latent heat of fusion
SLH for changing between solid and liquid (melting or freezing)
What is specific latent heat heat of vaporisation
SLH for changing between liquid and gas (boiling or condensing)
How can a change in pressure cause a change in volume (gases)
A gas exerts a force on its container due to collisions between particles in random directions, but add together to produce a net force at right angles to the wall of the container
If the pressure of a gas is increased (heating) this force increases
If the pressure of a gas is decreased (cooling) this force decreases
If the gas is in a container that can change volume, this can change the containers volume, and so the gas
Discuss pressure outside a container
This is for any container that can change volume
The outside of a gas container is under pressure from whatever’s around it
If the container isn’t expanding or contracting, the pressure and force of the gas inside the container pushing outwards is equal to the pressure and force of the air outside the container pushing inwards
If you increase the pressure of the gas inside the container, then the force pushing outwards will be higher than the force pushing inwards If you- net outwards force on thr walls of the balloon
Container expands
As the container expands, particles hit the wall less- pressure decreases
Once the pressures match up container stops expanding
Same thing but opposite for reducing pressure in container
How does doing work on a gas increase its temp
Doing work on a gas increases its internal energy
You can do work on a gas mechanically
The gas exerts pressure so exerts a force on it. Work has to be done against this force to push back
This transfers energy to kinetic stores of the gas, increases the internal energy and therefore temp
How far does the earths atmosphere stretch
100km
Is atmospheric pressure higher or lower at sea level
Higher - more air pressing down
What is upthrust
Overall upwards force
Discuss liquid pressure, floating + sinking
1) If you submerge (or partially submerge) an object in a liquid, it experiences liquid pressure from all directions due to the particles of the liquid.
2) This pressure increases with depth, due to the weight of the ‘column’ of liquid directly above the object.
3) Liquids can’t be compressed (or not very much), so their density is the same everywhere (unlike gases).
4)The pressure at a given depth (i.e. below a column of liquid of a given height) is given by the equation: pressure due to a column of liquid (Pa) = height of column (m) x density of liquid (kg/m°) x g (N/kg)
6) You can also use this equation to find the difference in pressure between two depths —
difference in pressure = difference in depth x density x g.
7) As pressure in a liquid increases with depth, the force pushing upwards on the bottom of an object due to the liquid pressure is greater than the force pushing down at the top of the object.
8) This causes an overall upwards force, called upthrust.
9) The upthrust acting on an object is equal to the weight of fluid it has displaced. If this upthrust is equal
10) So, to make an object float, you need to make it less dense than the liquid you’re trying to float it on — so it will have displaced a volume of water with a weight equal to its
