P1 - Matter

• Atom


  Tiny sphere that cannot be divided
• Dalton's atomic model


  • Everything is made of tiny spheres called atoms

  
• Thomson's plum pudding model


  • Atom has electrons embedded in a positive charge

  
• Rutherford's gold foil experiment


  • Most of the atom is empty space, with a small dense nucleus

  
• Bohr's atomic model


  • Electrons orbit the nucleus in specific energy levels

  
• Subatomic particles


  • Protons (relative mass 1, charge +1)
  • Neutrons (relative mass 1, charge 0)
  • Electrons (relative mass 0.0005, charge -1)
• Typical size of an atom is 1x10^-10 metres, with the nucleus being 10,000 times smaller
• Nearly all the mass of an atom is concentrated in the nucleus
• Energy levels


  Distances at which electrons lie from the nucleus

  
• Electron arrangements may change with interaction with electromagnetic radiation
• Density


  Mass per unit volume
• Solids and liquids have similar, higher densities as the space between particles does not change significantly
• Liquids typically have a lower density than solids, with the exception of ice which is less dense than water
• Gases have much lower densities as the spacing between atoms is much greater
• Mass is conserved during a change in state of a substance
• Physical changes are reversible and not chemical changes
• Temperature


  Measure of the average kinetic energy of particles in a system
• Heat


  Form of energy
• Specific heat capacity


  Energy required to raise the temperature of 1kg of a substance by 1°C
• Specific latent heat


  Energy required to change the state of 1kg of a substance without a change in temperature
• Particles in a fluid move randomly in every direction
• Pressure


  Force per unit area
• Temperature and pressure are proportional when volume is constant


  Increasing temperature increases pressure
• Volume and pressure are inversely proportional at constant temperature


  Increasing pressure decreases volume
• Temperature and volume are proportional at constant pressure


  Increasing temperature increases volume
• When work is done on a fluid, its temperature increases
• Earth's atmosphere is assumed to be isothermal and have uniform density
• Atmospheric pressure


  Total weight of air above a unit area at a certain altitude
• Atmospheric pressure decreases as height above Earth's surface increases
• An object will float if its weight is less than the weight of the fluid it displaces
• An object will sink if its weight is greater than the weight of the fluid it displaces
• Buoyancy force


  Upwards force exerted by a liquid on a partially submerged object
• Pressure due to a column of liquid


  Height of column x density of liquid x gravitational acceleration