thermal physics combined

• common (not si) unit for temperature


  °C
• si unit for temperature


  K (kelvin)
• si unit of energy transferred/work done


  J (joules)
• si unit of mass

  kg (kilograms)
• si unit of density

  kg/m³
• si unit of length


  m (metre)
• si unit of area

  m²
• si unit of volume

  m³
• si unit of speed/velocity

  m/s
• si unit of acceleration


  m/s²
• si unit of force


  N (newtons)
• si unit of pressure


  Pa (equivalent to N/m²)
• si unit for specific heat capacity

  J/kg°C
• explain why heating a system will change the energy stored within the system and raise its temperature or produce changes of state

  heating a system involves transferring energy to the particles of molecules within the system

  
  

  this increases the kinetic energy of the particles which means the internal energy of the system increases, which increases the temperature

  
  

  this can also produce a change of state if the energy supplied is used to overcome the forces holding the molecules together as opposed to increasing the kinetic energy

  this does not increase the temp. because no energy goes towards increasing the kinetic energy of the system
• label the points on this cooling graph (the points are the same on a heating graph except they are reversed in order)
• what is it called when a solid heats up into a liquid

  melting
• what is it called when a solid heats up into a gas

  subliming/sublimation
• what is it called when a liquid heats up into a gas

  boiling/evaporating
• what is it called when a gas cools down into a liquid

  condensation
• what is it called when a liquid cools down into a solid

  freezing
• is this substance a solid, liquid or gas and how can you tell by its arrangement and presumed motion

  solid:

  molecules close together in a fixed regular lattice pattern

  strong intermolecular forces of attraction

  molecules vibrate but can't move about
• is this substance a solid, liquid or gas and how can you tell by its arrangement and presumed motion


  liquid:

  molecules close together in random arrangement

  weaker intermolecular forces than solids

  molecules move around each other
• is this substance a solid, liquid or gas and how can you tell by its arrangement and presumed motion


  gas:

  particles far apart in random arrangement

  negligible/very weak intermolecular forces

  particles are constantly moving with random motion
• describe an experiment to show constant temperature during a change of state


  fill a beaker with boiling water

  put ice in the beaker and record the temperature of the ice every 10s as it melts

  the results should be a straight line on a temperature/time graph as the energy in the ice goes towards breaking the bonds in the ice rather than increasing its kinetic energy
• how is specific heat capacity defined and what is its si unit

  specific heat capacity is the amount of energy required to increase the temperature of 1kg of a substance by 1°C

  it is measured in J/kg°C
• what is the equation for change in thermal energy

  ΔQ = m × c × ΔT

  Change in thermal energy [J] = Mass [kg] x Specific heat capacity [J/kg 0C] x Change in temperature [0C]
• 5.14) describe an experiment to investigate the specific heat capacity of materials including water and some solids

  measure the mass of an insulating container, fill it with 200ml water and then measure the mass again (the difference between these numbers is the mass of the water)

  
  

  measure the temperature of water and turn on power which is connected to the water by a immersion heater and connect it to voltmeter and ammeter

  
  

  wait 1 minute and then measure the water temperature and take voltmeter and ammeter measurements

  
  

  calculate energy supplied using equation: energy supplied = voltage x current x time

  substitute the answer as Q in the equation Q=mcΔT to find specific heat capacity

  
  

  repeat 3 times to find an average

  plot graph
• 5.7) which changes occur to evaporate/ boil a liquid into a gas

  liquids have some kinetic energy

  
  

  as they are heated, particles vibrate more so their kinetic energy increases

  
  

  kinetic energy increases → particles vibrate more → frequency of collisions increases → particles get further away from eachother

  
  

  liquid reaches boiling point when particles are far away enough that their intermolecular forces break and they become gases
• 5.7) which changes occur to melt a solid into a liquid

  solids can't move so they have no net kinetic energy

  
  

  as they are heated, the particles vibrate so kinetic energy is gained

  
  

  kinetic energy increases → particles vibrate more → frequency of collisions increases → particles get further away from eachother and become liquid because they break free of their previous bonds
• how do molecules in a gas exert a pressure on the walls of a container


  gas molecules have rapid and random motion

  when they hit the walls of the container, they exert a force

  pressure = force/area and the force exerted from the gas molecules is spread out over the area of the container's walls
• why is 0K absolute zero

  at absolute zero the particles have no thermal energy or kinetic energy, so they stop moving

  this temperature is called 0K, which is equivalent to -273°C
• how to convert between Kelvin and Celsius scales

  C = K - 273

  K = C + 273

  K is always bigger than C
• why does an increase in temperature result in an increase in the average speed of gas molecules

  as you increase the temperature of a gas

  the kinetic energy of the gas particles increases

  so they move around with a greater average velocity/speed
• what is the relationship between the Kelvin temperature of a gas and the average kinetic energy of its molecules

  kelvin temperature is proportional to the average kinetic energy of its molecules
• explain the relationship between Kelvin temperature and pressure at constant volume (pressure law)

  as a gas is heated, kinetic energy of the particles increases so their average speeds increase

  
  

  this means there are more collisions per second with the wall, so they exert a greater average force on the wall

  
  

  this means that the total pressure exerted by the particles increases:

  pressure is force / area, and the force here increases while the area stays the same

  
  

  therefore the relationship between pressure and temperature is directly proportional (as pressure increases, temperature increases and vice versa)

  this assumes volume + mass are constant
• explain the relationship between pressure and volume at constant temperature (boyle's law)

  if temperature is constant, average particle speed is constant

  
  

  as

  volume decreases in a container, particle collision frequency per second increases

  this is because the same amount of particles are moving around in a smaller volume so they are more likely to hit the sides

  
  

  more collisions exerted per second on the sides means that the particles exert a greater force on the wall over a given time, so the average force exerted on the walls increases

  this means that the total pressure exerted by the particles increases:

  pressure is force / area, and the force here increases while the area stays the same

  this means that the relationship between pressure and volume is inversely proportional: as volume decreases, pressure increases and vice versa

  assumes constant temperature + mass
• equation for the relationship between the pressure and Kelvin temperature of a fixed mass of gas at constant volume


  P₁/T₁ = P₂/T₂

  temperature must always be in kelvin

  P₁ = (P₂*T₁)/T₂

  P₂ = (P₁*T₂)/T₁

  T₁ = (T₂*P₁)/P₂

  P₂ = (P₁*T₂)/T₁

  if youre arranging for P₁, you need to divide by the opposite letter and the opposite number so you need to divide by T₂. then put the other values (P₂*T₁) over the T₂
• equation for the relationship between the pressure and volume of a fixed mass of gas at constant temperature


  P₁V₁ = P₂V₂

  if youre arranging for P₁, put the value with the same number but the opposite letter underneath the dividing sign (so you put T₁ under the division sign), and then multiply the other numbers over the division sign

  so you get (T₂ * P₂)/V₁
• 5.3) equation for density

  density (kg/m3)= mass (kg) / volume (m3)
• 5.4) how can you find the density of a regular or irregular object


  regular objects

  measure the sides of the object using a ruler

  calculate the volume

  do mass/volume to find the density

  irregular objects

  submerge in eureka can and measure the volume of water displaced

  do mass/volume to find the density