energy

• What is the law of conservation of energy? Energy cannot be created or destroyed, only transferred
• energy stores: chemical, kinetic, thermal, gravitational potential energy, elastic, magnetic, electrostatic
• energy transfers

  Mechanically, electrically, heating, radiation
• what is the gravitational field strength for Earth

  9.8N/kg
• equation for weight

  mass x gravitational field strength
• what is power: the rate at which energy is transferred
• what is internal energy: total energy stored by the particles making up a substance or system
• what is an open system: where energy is transferred from a system to an environment meaning energy is lost
• what is a closed system: a closed system is where energy and matter cant enter or escape therefore the overall energy doesn't change
• what happens when you heat up a substance: increases the particles kinetic energy store, which increases their internal energy
• specific heat capacity: the amount if energy needed to raise the temperature of 1kg of a substance by 1°C
• what do you measure specific heat capacity

  J/kg°C
• how to perform specific heat capacity RP: place a beaker on a balance and press 0

  add the substance and record the mass

  place a thermometer and immersion heater into the substance

  read starting temperature of the substance

  wrap the substance in insulating foam to reduce thermal energy transfer to the surroundings

  connect a joulemeter to the heater

  time for 30 minutes

  read the number of joules which has passed into the immersion heater

  read final temperature of the substance

  
  

  rearrange the equation for change in thermal energy
• sources for inaccuracy for specific heat capacity RP: thermal energy passing out of the beaker into the air

  
  

  reduced by:

  use an insulator with low thermal conductivity

  
  

  not all the thermal energy passing into the substance

  
  

  reduced by:

  ensure the immersion heater is fully submerged

  
  

  incorrect reading of thermometer

  
  

  reduced by:

  electronic temperature probe
• input energy: input energy = useful energy + wasted energy
• equation for efficiency: Efficiency = useful output energy/total input energy
• What is a non-renewable resource? A resource that cannot replenished as it is used; it is finite.
• Types of non-renewable energy

  fossil fuels, nuclear
• fossil fuels: oil, coal, gas

  energy output ≈ 30MJ per kg

  
  

  non-radioactive waste, readily available, easy to produce energy

  
  

  will run out, increasing fuel costs, greenhouse emissions
• nuclear energy: uranium or plutonium

  energy output ≈ 300,000 MJ per kg

  
  

  no greenhouse gases, very high energy output

  
  

  radioactive waste, non-renewable, expensive to commission and decomission
• What is renewable energy? resources that can be replenished as it is used
• Types of renewable energy: solar, geothermal, tidal, biomass, hydroelectric, wind
• renewable energy sources impacts on environment: solar - no pollution

  geothermal - no pollution

  tidal - large areas are flooding, destroying habitats and wildlife

  biomass - greenhouse emissions, forests could be destroyed

  hydroelectric- local habitats are affected by the areas that need to be flooded to build dams

  wind- noisy , spoils view , no pollution
• solid features: particles are very close together in a regular pattern,

  in a fixed position,

  particles cannot move,

  vibrates on the spot and cannot be compressed
• Liquid features: particles are close with small spaces between them,

  particles can move and flow around each other,

  moves randomly in all directions at low speeds,

  fills the bottom of a container,

  fixed volume which means cannot be compressed
• Gas features: particles can move freely and fill available space,

  particles are far apart with large spaces between them,

  moves randomly in all directions at high speed,

  fills a container

  no fixed shape which means can be compressed
• density equation

  Density = mass/volume
• density RP regular shaped object: measure the mass of each object and record the results

  calculate and record the volume of each object

  calculate and record the densities
• density rp irregular object: measure the mass of the object

  fill a displacement can with water

  place object into displacement can which will cause water to be displaced and flow out the can through the spout

  measure volume of water displaced using a measuring cylinder which is the same as the volume of the object

  calculate density
• density of a liquid RP: measure mass of empty measuring cylinder

  measure out a volume of the liquid

  measure the mass of full measuring cylinder

  calculate density

  
  

  density = mass (full) - mass (empty) / volume
• changes of state: the temperature stays the same whilst the substance is melting/boiling, this is because the particles are breaking their bonds

  
  

  if the temperature is increasing this means it is not changing state and the particles move faster as they gain kinetic energy
• internal energy: energy stored stored inside a system by the particles that make up the system
• equation for internal energy: internal energy = kinetic energy + potential energy
• affect of temperature on gas pressure: temperature of a gas is the average kinetic energy of the molecules

  the higher the temperature , the greater the average kinetic energy and so the faster the average speed of the molecules
• what is gas pressure: the total force exerted by all the molecules inside of a container on a unit area (e.g. per m^2)
• relationship between volume and pressure: pressure and volume are inversely proportional,

  as one increases the other decreases
• equation for fixed mass of gas held at a constant temperature: constant = pressure x volume

  
  

  pressure, Pa

  volume, m^3

  pV = constant
• therefore ...

  P1 x V1 = P2 x V2