p1 - matter

• how did the plum pudding model describe the atom?

  a positively charged sphere with negatively charged electrons evenly distributed throughout it
• prior to the discovery of the electron, what was believed about the atom?

  the atom was believed to be indivisible
• which experiment lead to the plum pudding model being discarded?

  Rutherford's gold foil experiment
• what is the name given to the currently accepted model of the atom?

  Bohr nuclear model
• what are the three subatomic constituents of an atom?

  • electron
  • proton
  • neutron
• describe the arrangement of protons, electrons and neutrons in an atom

  • the protons and neutrons are found in the atom's nucleus
  • the electrons are found in discrete energy levels around the nucleus
• what type of charge does the nucleus of an atom have and why?

  • positive charge
  • the nucleus contains protons and neutrons
  • protons have a positive charge
  • neutrons have a neutral charge
• where is most of the mass of an atom concentrated?

  nucleus
• approximately what proportion of the total radius of an atom is the radius of the nucleus?

  • 1/10,000
  • this equals 0.01%
  • the nucleus is very small compared to the whole atom
• give an approximation for the radius of an atom

  • 1 x 10 ^ -10 metres
• definition of density and state the relevant equation with units

  • the mass per unit volume of a material
  • d = m/v
  • density (kg/m^3) = mass (kg) / volume (m^3)
• particle arrangement of a liquid

  • close together in an irregular arrangement
  • flow past each other

  
• particle arrangement of a solid

  • tightly packed in a regular arrangement
  • only vibrate

  
• particle arrangement of a gas

  • separated with no arrangement
  • move freely

  
• what is always conserved when a substance goes through a state change?

  mass
• five main ways that a substance can change state

  • melt
  • freeze
  • evaporate
  • condense
  • sublimate
• sublimation

  when a substance transitions from a solid straight to a gas without transitioning into a liquid in betweem
• how does a change of state differ from a chemical change?


  in a change of state the material can return to having its previous properties if the change is reversed
• what two things can heating a substance do?

  • raise its temperature
  • change its state
• specific heat capacity

  the amount of energy needed to increase the temperature of 1kg of a substance by 1 degree celcius
• what can be said about a material if it has a higher specific heat capacity?

  for a constant mass, the material will need more energy to achieve a given temperature change
• specific latent heat

  the amount of energy needed to change the state of 1kg of a substance without changing the temperature
• equation for the amount of energy needed to change state

  • E = m x L
  • energy to change state (J) = mass (kg) x specific latent heat (J/kg)
• what is the internal energy of a substance?

  • the energy stored by the particles
  • the sum of the total kinetic energy and potential energies that make up the system
• motion of molecules in a gas

  constant random motion
• unit for pressure

  pascal (Pa)
• ways to increase the pressure in a gas

  • increase the temperature
  • increase the volume of container
• why does pressure increase as temperature increases (at a constant volume)?

  • kinetic energy of molecules increase
  • more frequent collisions
  • greater rate of change of momentum
  • greater force and therefore greater pressure
• if gas A is at a low pressure, and gas B is at a high pressure, what can be said about the rate of collisions in each gas?

  • there are more collisions per second in gas B than in gas A
  • the rate of collisions is higher in B
• describe the forcethat the pressure of the gas exerts on the walls of its container

  • the net force acts at right-angles to the container's surface
  • the magnitude of the force increases as pressure increases
• explain how increasing the volume of a gas results in a decrease of pressure

  • molecules become more spread out so collisions become less frequent (more time between them)
  • this reduces the rate of collisions
  • rate of change of momentum decreases, and so force exerted on container decreases, resulting in a lower pressure
• what can be said about the product of pressure and volume for a fixed mass of gas at a constant temperature?

  • it is constant
  • p x V = constant
• what increases when you do work on a gas?

  • the internal energy of the gas
  • this can also lead to increase of temperature
• why does the temperature inside of a bike pump increase when it is pumped?

  • work is done on a gas when it is compressed
  • doing work on a gas increases its internal energy, so also increases the average kinetic energy of the molecules
  • temperature increases with an increase of average kinetic energy
• why does atmospheric pressure decrease as you move higher above the Earth’s surface?

  • the atmospheric pressure at a point is equal to the weight of the air in the column above that point
  • as you move higher above the Earth the amount of air in said column decreases
  • resulting in less weight above and as a result less pressure at the point
• what does an object in fluid experience as a result of pressure?

  forces at right angles to all of its surfaces
• does pressure in a fluid increase or decrease with depth?

  why?

  • increases
  • caused by the gravitational force on the fluid above that point
  • the deeper you go, the greater the weight of the water above you, and so a higher force and pressure
• what equation is used to calculate the pressure at a given depth of liquid?

  pressure = depth x liquid density x gravitational field strength
• upthrust

  the upwards force that an object experiences in a fluid as a result of greater pressure below the object than above it
• under what circumstances will an object float?

  when the objects upthrust equals its weight