Particle model of matter

• what is density?

  • the mass per unit volume of a material
• what is the relationship with mass and density

  • low mass = low density
• what is the density, mass, volume equation

  d = m/v
• why are gases less dense than solids

  • the particles are more spread out
• what is the unit for density

  g/cm3 or kg/m3
• what is the particle model

  • model which describes the arrangement and movement of particles in a substance
• what are solids

  • fixed
  • vibrate in place
  • have a definite shape
  • definite volume
• what are liquids

  • closely packed particles
  • can flow over one another
  • have no definite shape
  • have a definite volume
• what are gases

  • partciles are far apart
  • move randomly
  • dont have a fixed position
  • no fixed volume - they will compress/expand to fit any container
• why are gases highly compressible

  • large gaps between the particles
  • easy to push the particles together
• what kind of density do liquids and solids have?

  • high density
  • molecules are packed tightly together
• why do gases have a lower density

  • widely spaced
• what is internal energy

  • the total energy stored inside of a system by the particles that make up a system due to their motion and position
• what is internal energy made up of

  • kinetic store
  • potential store
• what does heating a system do to its internal energy

  • increases kinetic energy therefore increases the temperature
• how does a change of state occur

  • substance reaches a certain temperature and energy will stop being transferred to the kinetic stores
  • it is instead used to overcome intermolecular forces leading to a change of state
• what does the increase temperature of a system depend on?

  • the mass of the substance
  • type of material
  • energy input to the system
• what is specific heat capacity

  The specific heat capacity of a material is the energy required to raise one kilogram (kg) of the material by one degree Celsius (°C
• what is the equation for specific heat capacity

  Energy change = MCAT
• what does it mean for a substance to have low specicfic heat capacity

  • cools and heats quickly
  • less energy required to change temp
• what is latent heat

  • energy needed for substance to change state
• what happens to the temp of a substance when it changes state

  • it remains constant
  • because energy is used to overcome intermolecular forces of attraction rather than increasing kinetic energy
• what is specific latent heat

  • energy needed to change the state of 1kg of substance without changing the temp
• what are the two types of latent heat

  • fusion
  • vaporisation
• what is SLH of fusion

  • solid to liquid
  • liquid to solid
• what is SLH of vaporisation

  • Liquid to gas
  • gas to liquid
• what is SLH equation

  E= ML
• high kinetic energy = high temp
• what happens when you increase the temperature of a gas

  • you increase the kinetic energy
• how do gas particles create pressure?

  • gas particles move in random directions
  • when they collide they exert a force and a pressure
  • faster particles = more frequent collisions = more pressure
• what is the relation between volume and pressure

  inversly proportional

  • if you increase the volume, the pressure will decrease as there is more space so less collisions
• what is equation for fixed gas at constant temp

  pV=constant
• what is work

  • transfer of energy by a force
• what happens when you do work on a gas

  • increases internal energy
  • increases temperature
• how is work done on a gas

  • force is exerted by a piston which compresses the gas
  • molecules move around faster and have higher kinetic energy
  • temp increases
• what happens when a gas is expanded

  • the gas does the work
  • it looses energy and thereofre temperature decreases
• when measuring specific latent heat of water vapour, you heat water and see how long it takes to vaporise. How will the student's result be affected if enery is transferred to the surroundings whilst being heated

  • the value will be too high
  • because less energy is transferred to the water
• how is the specific latent heat of water affected if some of the water vapourises before it reaches 100 degrees?

  • the measured change in mass is too high
  • so the value is too low