SP14 Particle Model Flashcards
Define density
The mass per unit of volume
How do we calculate density?
mass/volume
What are the units for density?
g/cm^3 or kg/m3
What are the three states of matter?
Solids, liquids and gas
Why do solids and liquids have similar densities?
The space between the particles don’t change significantly
Describe the following for solids:
a) intermolecular force
b) arrangment
c) movement of particles
d) shape and volume
e) compressibility
a) very strong
b) close together, regular pattern
c) vibrate around a fixed point in space
d) fixed for both
e) not compressible
Describe the following for liquids:
a) intermolecular force
b) arrangment
c) movement of particles
d) shape and volume
e) compressibility
a) moderately strong
b) close together, randomly arranged
c) move around each other
d) takes shape of the container, fixed
e) almost negligible
Describe the following for gas:
a) intermolecular force
b) arrangment
c) movement of particles
d) shape and volume
e) compressibility
a) negligible
b) far apart, random arrangement
c) move quickly, in a straight line, in random directions until they collide: causing them to change directions
d) takes shape of container, expands to fill container
e) highly compressible
Why are gases compressible?
- large gaps between the particles
- makes it easier to push them as compared to solids and liquids
What doesn’t change during a change of state?
- mass
- number of molecules in the substance
What does change during a change of state?
- the state of matter of the substance
- the energy that the substance has
What happens when you heat up a system?
- the amount of kinetic energy that the particles have increases
- particles vibrate more
- temperature of the system increases / substance changes state
What are the two types of energy that molecules within a substance possess?
- kinetic energy
- potential energy
Define internal energy
The total energy stored inside a system due to their motions and position
What happens when a substance changes state?
- potential energy of molecules increases, breaking bonds between them and becoming further apart
- kinetic energy remains the same, which means that temperature remains the same, despite the substance continuing to be heated
Define specific heat capacity
The amount of energy required to raise the temperature of 1kg of a substance by 1degree celsius
What does the increase of temperature of a system depend on?
- mass
- type of material
- energy input into the system
What is a low heat capacity?
A substance that takes less energy to change its state: it heats up and cools down fast
What is a high heat capacity?
A substance that takes more energy to change its state: will heat up and cool down slowly
Define specific latent energy
The amount of energy that it takes to make 1 kg of a substance to change its state without a change in temperature
What are the two types of specific latent heat?
- fusion
- vapourisation
What are the units of specific latent heat?
joules per kilogram J/kg
Define specific latent heat of fusion
The thermal energy used to convert 1kg of solid into a liquid with no change in temperature
Define specific latent heat for vaporisation
The thermal energy required to convert 1kg of liquid to gas with no change in temperature
How do we calculate specific latent heat?
energy/mass = specific latent heat
What is the difference between specific latent heat and specific heat capacity?
- specific heat capacity = change in temperature in the same state
- specific latent heat = change in state, not in temperature
Name an equation involving specific heat capacity
change in thermal energy = mass x specific heat capacity x change in temperature
What is insulation used for?
To slow down the rate at which heat transfers from an object to its surroundings
How do we reduce conduction and convection?
Use thermal insulators
How do we reduce radiation?
Using shiny and reflective coatings to reflect IR radiation back into the system
Define pressure
Force exerted per unit area
What is the unit used to measure pressure?
Pascals (Pa)
Pressure produces a force to…
right angles of a surface
How is pressure of a gas caused?
Pressure is caused due to the force on the walls of a container caused by moving particles hitting a wall
Describe the relationship of the temperature and the pressure of a gas
- higher the temperature of the gas = the more energy the molecules have
- collisions happen more often
- and happen with greater impact
- which increases the pressure
Define absolute zero
Particles at this temperature have no kinetic energy at all, so they remain perfectly still and don’t vibrate at all
What is the temperature of absolute zero?
-273 degrees celsius, or 0 kelvin
How do we convert between celsius to kelvin?
add 273
How do we convert from kelvin to degrees celsius?
subtract 273
What happens to the volume when a gas is compressed?
It decreases
What happens to the volume when the gas is expanded?
It increases
What is the equation involving pressure and volume?
P1 X V1 = P2 X V2
What is work done?
The transfer of energy through a force
How is work done on a gas?
- through compression
- force used to push a piston by a certain distance
- which decreases the volume of gas
- causing the molecules to move faster = more kinetic energy = increase in temperature
How does a gas do work?
- when a gas expands
- it loses energy
- resulting in a decrease of temperature
