P1: Matter
Chapter 1.1: The particle model
2000 years ago
● People believed things could be split forever
● Two Greek philosophers (Democritus and Leucippus) thought it isn’t possible
● They believed it would end with an atom
● Atom (atomos meaning indivisible in Greek)
● They claimed atoms were too small to see
1870’s
● John Dalton did experiments to measure how elements combined
● Believed his experiments could be explained with atoms
● Created a model of an atom
● He thought that all atoms in an element are the same and the atoms in one element are
different to the atoms in the other elements
1897
● J. J. Thomson was investigating rays given out by hot metals, called cathode
rays
● He discovered that they are made up of particles that have one thousandth the
mass of a hydrogen atom
● He had found a particle called an electron that must have come from inside an
atom
● He also worked out the charge of an electron is negative
● Atoms overall have no electrical charge - neutral
● Thomson suggested a new model
● He said that atoms are like blueberry muffins
● In the model, the atom consists of positive mass with negative electrons
● Did not know what the mass was made of, or the structure
● Thought it might be solid or like a cloud
1909
● Ernest Rutherford discovered some materials emit particles
● Called them alpha particles - have positive charge
● Decided to fire them at a piece of gold foil
● Hans Geiger and Ernest Marsden helped him with work
● Most of particles went through, but a few bounced back
● Could not be explained by Plum Pudding model
● Suggested atom is made of tiny, positively charged
nucleus with electrons around outside
● Nearly all mass of atom is in nucleus
● When alpha particles hit nucleus they bounce back
● Later, scientists discovered nucleus is made of 2 types of
particles: neutrons and protons
1913
● Problem with Rutherford’s model: you would expect electrons to spiral in until they hit nucleus
● Niels Bohr suggested electrons can only move in fixed orbits called shells around nucleus
● Modern atomic structure
,Atom is about 0.000,000,0001m in diameter. Standard form: 1x10-10m
Chapter 1.2: Changes of state
Density
● Tells you how much mass is in certain volume
3 𝑚𝑎𝑠𝑠(𝑘𝑔)
● Formula: 𝑑𝑒𝑛𝑠𝑖𝑡𝑦(𝑘𝑔/𝑚 ) = 3
𝑣𝑜𝑙𝑢𝑚𝑒(𝑚 )
● Solid is most dense, gas is least dense
● Depends on particles arrangement ^^ and mass of particles
● Conservation of mass:
○ Have to add or remove material for mass of a system to change
○ Particles do not appear or disappear - Law of Conservation of Mass
○ Applies when substances change state
Energy and temperature
● Temperature
○ tells you how hot or cold something is
○ Can be measured by thermometer or temperature sensor
○ Can be measured in Celsius, Fahrenheit or Kelvin
○ Difference in temperature of 1oC is same as 1K
● Difference between energy and temperature
○ When water is heated, energy from chemical store of fuel is transferred to thermal
store of water
○ Water particles move faster or vibrate more
○ Energy in thermal store is measured in joules - depends on arrangement of particles
and how fast they are moving or vibrating
○ Temperature tells you average kinetic energy of particles
● What happens when you heat things up?
○ Changes energy stored within the system to increase the temperature
○ Produces a change of state
○ makes chemical reactions happen
○ Changes of state are physical changes
■ Does not make new substances
■ Most are easy to reverse
■ Particles are only rearranged
○ Chemical reactions are different
■ Involves joining atoms together in different ways
■ Cannot be easily reversed
Specific heat capacity
● Amount of energy needed to raise temperature of an object depends on
○ Type of material
○ Mass of material
○ Temperature rise
● Energy needed to raise temperature of 1kg of a material by 1oC is specific heat capacity
● Heating increases internal energy of material
● Internal energy: energy that relates to motion, vibration, rotation and arrangement of particles
● How to calculate using specific heat capacity: change in thermal energy (J) = mass (kg) x
specific heat capacity (J/kgoC) x change in temperature (oC)
● Specific heat capacity how resistant material is to change in temperature
, Specific latent heat
● During change of state internal energy increases but temperature does not
● Specific latent heat of fusion (or melting) is energy transferred when 1kg of substance
changes between liquid and solid
● Specific latent heat of vaporisation is energy transferred when 1kg of substance changes
between liquid and gas
● How to calculate with specific latent heat: thermal energy for change in state (J) = mass (kg) x
specific latent heat (J/kg)
● Difference between specific latent heat and specific heat capacity: SLH is about change of
state, SHC is about change of temperature
Chapter 1.3: Pressure
Pressure from gases
● When balloon is blown up, there are more air particles inside
● Particles collide with surface of balloon
● Each collision produces small force
● Many collisions produces outward force over certain area
● Produces gas pressure
● Force on rubber makes balloon bigger
● When you add air particles to container that cannot expand, pressure increases
Effect of temperature on gas pressure
● Higher temperature of gas means particles have higher average
speed
● Slides more frequently with sides of container
● Forms bigger force and more pressure
● Pressure gauge can be used to measure pressure of air trapped in
bottle
● Measured in pascals (Pa)
● One pascal = one newton per square metre (1 N/m2)
● For higher pressure, use kilopascals
Extrapolating
● Dotted line shows what would happen
if you continued cooling gas
● Pressure would reach 0 Pa at
-273.14oC, or 0K
● Not possible to reach absolute zero,
but value can be worked out by
extrapolating
Measuring pressure of gas
● Manometer
Chapter 1.1: The particle model
2000 years ago
● People believed things could be split forever
● Two Greek philosophers (Democritus and Leucippus) thought it isn’t possible
● They believed it would end with an atom
● Atom (atomos meaning indivisible in Greek)
● They claimed atoms were too small to see
1870’s
● John Dalton did experiments to measure how elements combined
● Believed his experiments could be explained with atoms
● Created a model of an atom
● He thought that all atoms in an element are the same and the atoms in one element are
different to the atoms in the other elements
1897
● J. J. Thomson was investigating rays given out by hot metals, called cathode
rays
● He discovered that they are made up of particles that have one thousandth the
mass of a hydrogen atom
● He had found a particle called an electron that must have come from inside an
atom
● He also worked out the charge of an electron is negative
● Atoms overall have no electrical charge - neutral
● Thomson suggested a new model
● He said that atoms are like blueberry muffins
● In the model, the atom consists of positive mass with negative electrons
● Did not know what the mass was made of, or the structure
● Thought it might be solid or like a cloud
1909
● Ernest Rutherford discovered some materials emit particles
● Called them alpha particles - have positive charge
● Decided to fire them at a piece of gold foil
● Hans Geiger and Ernest Marsden helped him with work
● Most of particles went through, but a few bounced back
● Could not be explained by Plum Pudding model
● Suggested atom is made of tiny, positively charged
nucleus with electrons around outside
● Nearly all mass of atom is in nucleus
● When alpha particles hit nucleus they bounce back
● Later, scientists discovered nucleus is made of 2 types of
particles: neutrons and protons
1913
● Problem with Rutherford’s model: you would expect electrons to spiral in until they hit nucleus
● Niels Bohr suggested electrons can only move in fixed orbits called shells around nucleus
● Modern atomic structure
,Atom is about 0.000,000,0001m in diameter. Standard form: 1x10-10m
Chapter 1.2: Changes of state
Density
● Tells you how much mass is in certain volume
3 𝑚𝑎𝑠𝑠(𝑘𝑔)
● Formula: 𝑑𝑒𝑛𝑠𝑖𝑡𝑦(𝑘𝑔/𝑚 ) = 3
𝑣𝑜𝑙𝑢𝑚𝑒(𝑚 )
● Solid is most dense, gas is least dense
● Depends on particles arrangement ^^ and mass of particles
● Conservation of mass:
○ Have to add or remove material for mass of a system to change
○ Particles do not appear or disappear - Law of Conservation of Mass
○ Applies when substances change state
Energy and temperature
● Temperature
○ tells you how hot or cold something is
○ Can be measured by thermometer or temperature sensor
○ Can be measured in Celsius, Fahrenheit or Kelvin
○ Difference in temperature of 1oC is same as 1K
● Difference between energy and temperature
○ When water is heated, energy from chemical store of fuel is transferred to thermal
store of water
○ Water particles move faster or vibrate more
○ Energy in thermal store is measured in joules - depends on arrangement of particles
and how fast they are moving or vibrating
○ Temperature tells you average kinetic energy of particles
● What happens when you heat things up?
○ Changes energy stored within the system to increase the temperature
○ Produces a change of state
○ makes chemical reactions happen
○ Changes of state are physical changes
■ Does not make new substances
■ Most are easy to reverse
■ Particles are only rearranged
○ Chemical reactions are different
■ Involves joining atoms together in different ways
■ Cannot be easily reversed
Specific heat capacity
● Amount of energy needed to raise temperature of an object depends on
○ Type of material
○ Mass of material
○ Temperature rise
● Energy needed to raise temperature of 1kg of a material by 1oC is specific heat capacity
● Heating increases internal energy of material
● Internal energy: energy that relates to motion, vibration, rotation and arrangement of particles
● How to calculate using specific heat capacity: change in thermal energy (J) = mass (kg) x
specific heat capacity (J/kgoC) x change in temperature (oC)
● Specific heat capacity how resistant material is to change in temperature
, Specific latent heat
● During change of state internal energy increases but temperature does not
● Specific latent heat of fusion (or melting) is energy transferred when 1kg of substance
changes between liquid and solid
● Specific latent heat of vaporisation is energy transferred when 1kg of substance changes
between liquid and gas
● How to calculate with specific latent heat: thermal energy for change in state (J) = mass (kg) x
specific latent heat (J/kg)
● Difference between specific latent heat and specific heat capacity: SLH is about change of
state, SHC is about change of temperature
Chapter 1.3: Pressure
Pressure from gases
● When balloon is blown up, there are more air particles inside
● Particles collide with surface of balloon
● Each collision produces small force
● Many collisions produces outward force over certain area
● Produces gas pressure
● Force on rubber makes balloon bigger
● When you add air particles to container that cannot expand, pressure increases
Effect of temperature on gas pressure
● Higher temperature of gas means particles have higher average
speed
● Slides more frequently with sides of container
● Forms bigger force and more pressure
● Pressure gauge can be used to measure pressure of air trapped in
bottle
● Measured in pascals (Pa)
● One pascal = one newton per square metre (1 N/m2)
● For higher pressure, use kilopascals
Extrapolating
● Dotted line shows what would happen
if you continued cooling gas
● Pressure would reach 0 Pa at
-273.14oC, or 0K
● Not possible to reach absolute zero,
but value can be worked out by
extrapolating
Measuring pressure of gas
● Manometer
