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Density and pressure/ ideal gases - Coggle Diagram
Density and pressure/ ideal gases
density and pressure
Density
The mass per unit volume of a material
equation
p=m/V
where
p= density--> in kilograms per meter cubed
m=mass--> in kilograms
V=volume--> measured in meters cubed
Units in density can change depending on the mass and volume
if measured in g and cm³
the density will be in g/cm³
if measured in kg and m³
The density will be in kg/m³
Practical
determining density of regularly shaped objects
method
Use a ruler, variner capillers or another apparatus to measure the
Repeat the process and get an average to the measurement and then calculate the density
Place the object in a digital balance and note down the mass
Determining density of irregular shaped objects
method
Place an empty measuring cylinder below the spout
lower the object to the eureka can
Fill the eureka can with water up to a point just below the spout
measure the volume of water displaced to the measuring cylinder
place the object on a digital mass balance and note down the mass
Repeat the process and make an average to calculate the amount the density
https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=1920/https://cdn.savemyexams.com/uploads/2020/05/Eureka-can.png
Measuring the density of liquids
method
Fill the cyliner with the liquid and measure the volume
Note down the new reading on the digital balance and subtract the new new mass from the original mass
place down a measuring cylinder on a digital balance and measure its weight
Repeat these measurements and take an average before calculating the density
Pressure
The concentration of a force or the force per unit area
equation
p=f/a
where
p=pressure
measured in pascals (Pa)
f=Force
measured in N
a=cross sectional area
measured in m²
Examples of pressure
Low pressure
tractors
THis means the force is spread out over a greater area
Resulting in less pressure
Tractors have large tires
high pressure
nails
Concentrates the force in a small area
This means there is a lot more pressure
sharp pointed ends
Pressure of fluids
a fluid is a liquid or a gas
Properties of pressure in fluids
The pressure exerted on objects in fluids creates forces against surfaces
The forces act at a 90º to the surface
pressure is exerted evenly across all the surface of the fluid and in all directions
Calculating pressure in a liquid
equation
P=h x p x q
where
P=pressure
measured in pascals (Pa)
h= height or depth of the fluid column above the object
measured in meters (m)
p=density of the fluid
measured in kilograms per meters cubed (kg/m³
q=
gravity
Ideal gases
kinetic theory
molecules in a gas are in constant random motion at high speeds
particles move their direction if they collide with
with the walls of its containers
Collision with the container produces a force at right angles to the wall of the container
A gas with a higher pressure means collision is more common resulting in a greater force being exerted to the walls
with another molecules
The random motion of particles in fluids is known as Brownian motion
Brownian motion provides evidence that air is made of small particles
This is because we can see how large molecules like pollen moves randomly which is a result of pollen colliding with smaller particles
Absolute zero
The amount of pressure exerted by a gas to its container is dependent on the temperature of the gas
This happens because at higher temperatures particles move faster causing collisions more commonly
There is a temperature at which the temperature is so low where particles don't move anymore and hence not colliding with the container
This temperature is absolute zero
absolute zero is equal to -273ºC
IN absloute zero it is impossible to remove more energy from a material
The temperature at which the molecules in a substance have zero kinetic energy
The kelvin scale
The kelvin scale starts at absolute zero
0K is equal to -273ºC
an increase of 1k equals to an increase of 1ºC
kelvin scale relative to ºC
https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=750/https://cdn.savemyexams.com/uploads/2021/04/14.1-K-and-Celsius-conversion-chart.png
Temperature and kinetic energy
The temperature of a gas is a measure of the average speed of the molecules
the higher the temperature the faster the avarage speed of the molecules
The lower the temperature, the slower the average speed of the molecules
Heating a system will change the energy stored in a system by increasing the kinetic energy of its particles
An increase in kinetic energy will cause the particles to travel at a higher speed which results in more collisions and more pressure
An increase in knetic energy can cause
Cause an increase in tempreature of the system
Produce a change in state
Internal energy
the sum of kinetic energy of all molecules
If a system is heated up the internal energy will increase
when the particl eis heated the particles speed up and create more collisions
Relationship between temperature and average kinetic energy
The temperature in kelvin is proportional to the average kinetic energy of the molecules
T ∝ KE
Gas laws
gas laws provide explanations for the relationship between
pressure and volume at a constant temperature
compressed
Decreases the volume which increases the pressure
expanded
Increases the volume, which decreases the pressure
A change in pressure can cause a change in volume
example using a vacuum pump
https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=750/https://cdn.savemyexams.com/uploads/2021/08/14.2.3-Vacuum-pump.png
As the gas has to travel a shorter distance to hit another object this means collisions will be more common, increasing the pressure
Pressure and (kelvin) temperature at a constant volume
If the temperature increases
the avarage speed of the molecule increases
This results in more collisions and a higher pressure
If the temperature decreases
The avarage speed of the molecule decreases
This means less collisions resulting in less pressure
The motion of particles can change depending on the temperature
THe pressure law
If the volume of an ideal gas is constant the pressure law is
pressure is proportional to the temperature
P ∝ T
The relationship between the pressure and kelvin temperature
P1/T1=P2/T2
where─
P1
Initial pressure
P2
final pressure
T1
initial temperature
T2
Final tempreature
Happens for a fixed mass of gas at constant volume
Boyle's law
pressure and volume are a constant
pV=constant
This means that pressure and volume are inversly proportional
When volume decreases the pressure increases
When the volume increases the pressure decreases
comparing the pressure and volume before and after a change in a gas
P1V1=P2V2
where
V1
initial volume
P2
final pressure
P1
initial pressure
V2
final volume