5.1 thermal physics

• what is thermal equilibrium?

  when two objects are in thermal equilibrium there is no net flow of thermal energy between them, therefore have the same temperature.
• how do you convert from celsius to to kelvin?

  Kelvin = Celsius + 273
• what is the absolute scale of temperature?

  uses the triple point of water and absolute zero as its fixed points
• what is the SI unit for temperature?

  kelvin
• what is the kinetic model?

  it describes how all substances. are made up of atoms or molecules, which are arranged differently depending on the phase of the matter.
• what is the kinetic model of solids?

  atoms, molecules are regularly arranged and packed closely together

  they have strong electrostatic forces between them

  atoms have fixed positions but can vibrate
• what is the kinetic model of liquids?

  atoms, molecules are still very close together but have more kinetic energy that atoms in solids therefore they can change position and slide past each other
• what is the kinetic model of gases?

  atoms and molecules have the most kinetic energy in gases.

  they are free to move past each other and electrostatic forces are negligible apart from in collision

  they move at random speeds in random directions
• what is brownian motion?

  random motion of particles suspended in a fluid
• what can we use to experiment brownian motion?

  smoke particles and microscope (or pollen with water)
• what are the key observations of the brownian motion experiment?

  only smoke particles were visible - they are much bigger compared to air particles

  particles moved with random motion - this is due to them colliding with air particles

  kinetic energy of smoke particles is the same as kinetic energy of air particles
• what is internal energy?

  sum of kinetic and potential energies of atoms or molecules in a substance
• how do you increase internal energy?

  increase temperature
• what happens to internal energy when the substance is heating up?

  internal energy increases
• what happens to kinetic energy when the substance is heating up?

  kinetic energy increases
• what happens to potential energy when the substance is heating up?

  potential energy remains constant
• what happens to internal energy when the substance is melting?

  internal energy increases
• what happens to kinetic energy when the substance is melting?

  kinetic energy remains constant
• what happens to potential energy when the substance is melting?

  potential energy increases
• what is the electrostatic energy in gasses?

  0J
• what is the electrostatic energies in liquid?

  slightly negative
• what is the electrostatic energies in solids?

  very negative
• what does negative electrostatic energy mean?

  energy must be supplied to the substance to break atomic or molecular bonds
• what is absolute zero?

  when particles have minimum internal energy. kinetic energy is 0 and potential energy is minimum.
• why is potential energy not 0 at 0 kelvin?

  there is still electrostatic potential energy stored between the particles
• what is specific heat capacity?

  the energy required to raise the temperature of a unit mass of substance by 1 degrees
• what is the units for specific heat capacity? 


  J kg^-1 K^-1
• what do the components of this equation represent?

  c = specific heat capacity

  E = energy transferred in Joules

  m = mass in kg

  delta theta = change in temperature

  
• what does this diagram represent?

  equipment used to determine specific heat capacity of a solid

  
• what does this diagram represent?

  equipment to determine specific heat capacity of a liquid

  
• what doe this diagram represent?

  heating circuit used when determining the specific heat capacitance of a material

  
• what are the components of a heating circuit used to determine specific heat capacity?

  variable resistor

  ammeter

  voltmeter

  power supply
• how do you work out energy transferred in a specific heat capacity experiment?

  E = V I t
• what graph do you plot to calculate specific heat capacity?

  time against temperature graph
• what is specific latent heat?

  energy required to change the phase of a unit mass while at constant temperature
• what is specific latent heat of fusion?

  energy required to change a unit mass from solid to liquid at constant temperature
• what is specific latent heat of vaporisation?

  energy required to change the phase of a unit mass from liquid to gas at constant temperature
• how do you work out latent heat of fusion?

  • calculate mass of ice melted in a fixed time without the heater
  • calculated mass of ice melted by heater only
  • E = V I t
  • E = mL

  
• what does the diagram below represent?

  equipment to calculate latent heat of vaporisation

  
• why is Lv greater than Lf?

  there is a greater difference in internal energy between a liquid and a gas then there is between a solid and a liquid