Tutorials

• Kinetic Theory of Matter

  All matter is composed of atoms and molecules that are in a constant state of constant random motion
• Temperature


  The average kinetic energy of the atoms and molecules of a substance
• Brownian motion


  Small pieces of matter in a fluid - flecks of dust, pieces of pollen, smoke particles, etc. - seem to vibrate randomly because they are being constantly hit from all sides by the molecules of the fluid (water, air, etc.)
• Thermal expansion


  The property of most matter that matter expands as heated and contracts as cooled. All matter is in a constant state of motion, the faster they move, the more space they need to move in and push the other molecules away. Thus as solids and liquids (phases of matter with definite volumes) increase temperature, the molecules move more and take up more space, so the substance increases in size.
• Diffusion


  The quality of matter that substances in materials where atoms are free to flow (gases or liquids), small particles put into the fluid tend to spread out randomly until they are evenly mixed (go from areas of high concentration to low concentration). This happens because both the fluid and the particles are constantly moving, so will be pushed and dragged around by other molecules until they mix evenly.
• Thermometer


  When the molecules of the fluid change temperature, say upwards, they move more, this causes them to take up more space (thermal expansion). The fluid in the thermometer has nowhere else to go, so it rises up the tube. The reverse is true for falling temperatures.
• Nothing can be cooled to below absolute zero
• Properties of states of matter

  • Relative bond strength
  • Particle movement
  • Particle organization
  • Type of shape
  • Type of volume
• Phase change


  The temperature doesn't change, because all the energy gained or lost by the substance just goes to changing the state of matter, not the temperature (the energy gained breaks bonds of attraction between neighbouring molecules instead of changing their speed, or the energy lost goes to forming bonds of attraction between neighbouring molecules instead of changing their speed)
• Pressure of gas in closed container decreases, volume stays same


  Temperature decreases (atoms are moving slower so they hit the walls not as hard)
• Pressure of gas in closed container decreases, temperature stays same


  Volume increases (particles are moving the same speed but don't hit the walls as often when the volume increases)
• Pressure of gas in closed container increases, volume stays same


  Temperature increases (atoms hit the walls harder so they move faster)
• Speed of gas in closed container increases, volume and number of particles stays same


  Pressure increases (they hit each other and the walls of the container harder)
• 0°C water has more internal energy than 0°C ice
• 0°C water and 0°C ice have the same average kinetic energy
• 0°C water has more stored energy than 0°C ice
• Temperatures below absolute zero (-273°C, 0K, or -459.7°F) are not possible
• Understanding a process or concept is better than memorizing different aspects
• Categories of mechanical waves

  • Transverse waves
  • Longitudinal waves
  • Surface waves (Mixed)

  
• Transverse waves


  • The medium moves perpendicular to the wave direction

  
• Longitudinal waves


  • The medium moves parallel to the wave direction

  
• Surface waves (Mixed)


  • Both transverse and longitudinal waves mix in a single medium
• Electromagnetic waves travel in a vacuum whereas mechanical waves do not
• Mechanical wave is generated by the vibration of a particle in any material medium
• Electromagnetic wave is generated by the accelerated motion of a charged particle
• Mechanical waves are caused by wave amplitude and not by frequency
• Electromagnetic Waves are produced by vibration of the charged particles
• Mechanical waves can be both transverse and longitudinal but an electromagnetic wave is a transverse wave
• Electromagnetic waves move at a constant speed, which is the speed of light in vacuum is 3 x 108 m/ s
• Mechanical waves propagate at different speeds in different media
• Speed of an electromagnetic wave is inversely proportional to the refractive index of the medium
• Speed of sound wave depends on the elastic properties of the medium
• An electromagnetic wave is called just a disturbance, A mechanical wave is considered a periodic disturbance
• Reflection of a wave

  When waves bounce off a barrier and head in a different direction

  
• Reflection of waves off straight barriers

  1. Waves approach the barrier

  2. Waves reflect off the barrier

  3. Angle of approach equals angle of reflection

  
• Reflection of waves off parabolic barriers

  1. Waves approach the parabolic barrier

  2. Waves reflect and converge at a focal point

  
• Refraction of a wave

  Change in direction of waves as they pass from one medium to another, accompanied by a change in speed and wavelength

  
• Water waves travel fastest when the medium is the deepest
• As water waves travel from deep water to shallow water, the speed decreases, the wavelength decreases, and the direction changes

  
• Diffraction of a wave

  Change in direction of waves as they pass through an opening or around a barrier in their path