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P2 (Energy stores, Energy sources, Thermal expansion, Kinetic molecular…

- - - - When system is in equilibrium, nothing changes, and so nothing happens
      - When there is a change to system, energy is transferred
  - - - Energy transfer pathways are
        
        Mechanical
        
        When force acts on object e.g. pulling, pushing, stretching, squashing
        
        Electrical
        
        Charge (Current) moving through potential difference e.g. charge flowing around a circuit
        
        Heating
        
        Energy is transferred from hotter object to colder one
        
        Radiation
        
        Energy transferred by electromagnetic waves e.g. light
  - - - ΔEP = Change in gravitational potential energy
      - m = mass
      - g = gravitational field strength
      - Δh = change in height
  - - - Ek = 1/2 x m x v^2
      - Ek = kinetic energy in joules, M = mass of object, v = speed of object
  - - - Total amount of energy transferred into system must be equal to total amount of energy transferred away from system
        
        Energy cannot be lost, but can be transferred to surroundings
        
        Energy can be dissipated to surroundings be heating and radiation
        
        Dissipated energy transfers are often not use in which case they can be described as wasted energy
    - - Energy stores and transfers can be represented using flow diagram
      - Shows both store and transfers taking place within a system
  - - - W = Fd
        
        Work = force x distance
    - - If force acts in direction an object is moving, the object will gain energy
      - if force acts in opposite direction to movement then object will lost energy
      - W space equals space F d space equals space increment E
  - - - the rate of this enegry transfer, or rate of work done is called power
    - - Rate of doing work
      - Work done = energy transferred
      - Formula P = W/t or P = ΔE/t
        
        W or ΔE = work done, or energy transferred
        
        t = time
        
        P = power
  - - - If a system has high efficiency, means most of the energy transferred is useful
      - System has low efficiency, means most of energy transferred is wasted
    - - Efficiency = useful energy output / total energy output x 100
      - In terms of power
        
        useful power output / total power input x 100
- - - - Sun heats up atmosphere, creating wind and producing waves
      - Water evaporated by sun falls as rain, filling up reservoirs
      - Plants grown using sunlight from basis for fuels - both biofuels and fossil fuels
    - - Geothermal
        
        Comes from heart produced in earth's core
      - Nuclear
        
        comes from elements which make up small proportion of earth's crust
        
        Tidal
        
        Comes from mainly gravitational attraction of the moon
    - - Energy from sun that falls on earth is transferred by radiation
        
        Most visible light and infrared radiation
        
        Amount of energy transferred from the sun to the earth each hour is equal to energy use of the world for one yaer
      - Solar cells transfer energy from sunlight electrically producing a current, and therefore generating electricity
        
        Number of cells connected together can supply electricity to homes
        
        Energy generated from solar cells can be stored in batteries for later use
      - Solar panels
        
        Transfer energy from sunlight to thermal store of solar panels which is used to heat water in pipes
        
        Solar pipes can be used to warm domestic water supplies
        
        Can reduce cost of producing hot water since it is heated partially by solar panels
        
        Solar furnaces
        
        Consist of large curved mirrors that focus the sun's rays on to a small area
        
        Can be used to boil water, generating enough steam to turn turbines and generate electricity in power station
        
        water is stored in a water tank and pumped through small pipes running through the solar panel
        
        Water is stored in a water tank and pumped through small pipes running through solar pannel
        
        Infrared radiation from sun heats water in pipes as it flows through them
        
        Water returns to tank at a higher temp
        
        Water may still need to be heated further to reach desired temperature
        
        Advantages
        
        Solar farms produce no greenhouse gases or pollution
        
        In many places on earth sunlight is a reliable energy source
        
        Solar energy is a renewable resource
        
        Disadvantageess
        
        Solar furnaces need to be large scale to produce high temps
      - Advantages
        
        Renewable and reliable
        
        No pollution
        
        Reduces household electricity drawn from national grid
      - Disadvantages
        
        Individual cells do not produce much electricity
        
        Solar cells are expensive
        
        need to be kept clean
  - - - Fossil fuels are
        
        Coal
        
        Crude oil (refined in petrol, diesel and other fuels)
        
        Natural gas (mostly methane) which is used in domestic boilers and cookers
      - Formed from remains of plants and animals
        
        Energy from the sun was transferred to chemical energy store of plants by photosynthesis
        
        Animals ate plants and energy transferred to their chemical store
        
        Energy is stored in chemical store of fossil fuels
      - Advantages
        
        Reliable
        
        Available
      - Disadvantages
        
        Non-renewable
        
        Combustion releases
        
        Pollutants
      - Uses of fossil fuels
        
        Transport
        
        generating electricity
        
        Heating
  - - - Stream turns a turbine
        
        Turbine turns a generator
        
        Generator generates electricity
  - - - Energy is released from the nuclear store of the fuel
    - - No pollutants are released
      - Safe
      - Reliable
    - - Non-renewable
      - Produces radioactive waste
      - Accidents can be catastrophic
  - - - Ethanol or methane can be produced and used in place of fossil fuels
        
        However they have half the energy density of fossil fuels
    - - Renewable
      - Carbon neutral
      - No sulphur dioxide
    - - Takes time for crops to grow
      - Resources could be used to grow food
  - - - Uses motion of water waves to turn turbines
      - Tidal power
        
        uses the motion of water at changing tides to turn turbines
      - Advantages
        
        No pollution
        
        Renewable
        
        Reliable
      - Disadvantages
        
        Expensive to build
        
        Damage to habitats
    - - Use motion of water to turn turbines
      - Advantages
        
        Renewable
        
        Reliable and available
        
        Suitable for large scale
      - Disadvantages
        
        Destroys habitats
        
        Some designs use pumps which release greenhouse gases
  - - - This geothermal energy heats up the rocks, sometimes to a high temp
    - - Steam can also be used to turn a turbine and generate electricity, and hot water can be used to heat homes
    - - Renewable soururce
      - Reliable source
      - Geothermal power stations are usually small compared to nuclear or fossil fuel power stations
    - - Few suitable locations on earth so small scale production of electricity
      - Can result in release of greenhouse gases from underground
      - Expensive to build
  - - - Nuclear fission involves collision (and bonding) of hydrogen nuclei to form helium nuclei, releasing nuclear energy in the process
- - - - Thermal expansion
      - Electrical resistance
      - Potential difference
      - Physical property that varies with temperature
    - - Fixed point - usually the boiling point and melting point of water
      - To define a temp scale, two reference temps called fixed points must be useed
      - Celcius scale is defined by freezing point of water (0) and boiling point of water (100)
    - - Divisions between two fixed points
  - - - Liquid expansion
      - Convenient to carry
      - Limited range 0-100
      - Delayed temp reading
    - - Voltage differences
      - Large range and accuracy
      - Instant temp readings
  - - - Energy contained within the system
      - If object is heated, since particles gain more energy, internal energy is increased
    - - Amount of energy required to change the temp of an object by one unit (1c)
    - - Amount of energy needed to raise temp of object per unit mass
      - Energy required to raise temp of 1KG material by 1 degrees celcius
    - - Energy = mass X Specific heat capacity x temp change
  - - - Once melting point is reached, solid will turn into a liquid
        
        During transition, temp is constant
        
        Once solid is fully melted, temp of liquid rises again
    - - Energy required to melt a solid at melting point
  - - - Once BP reached, temp stays constant as liquid becomes gas
        
        Once liquid has fully boiled into gas, temp of gas begins to rise
    - - Energy required to vaporize liquid at boiling point
      - Energy required to vapourize 1kg of liquid at boiling point with no change in temp
- - - - hence increase temperature
  - - - Stronger collisions against container wall
        
        Exerts more force on container wall
        
        increases pressure
    - - Stronger + more frequent collisions against container wall
        
        Exerts more force on container wall
        
        Increases pressure
    - - pV = constant
        
        p = pressure, v = volume
  - - - Not rigid
        
        No fixed shape
        
        No fixed volume
    - - Not rigid
        
        No fixed shape
        
        Fixed volume
    - - Rigid
        
        Fixed shape
        
        Fixed volume
  - - - Higher temp
      - Larger surface area
      - More air flow over surface of liquid
- - - - When one end of metal is heated, particles gain kinetic energy and vibrate quicker
        
        Causes neighboring particles to vibrate quicker and results in domino effet across structure
        
        Through transfer of kinetic energy in form of vibrations, heat is transferred from one end to the other
        
        Free electrons are highly mobile and rapidly quickens transmission of energy
  - - - Absence of free electrons makes passage of vibrations / kinetic energy difficult
    - - Water is boiled
  - - - Process requires movement of particles, may only occur in liquids or gases
  - - - Apart of electromagnetic spectrum, emitted by any hot object
      - Infrared can be emitted, abosrbed or reflected
      - Different types of surfaces can affect emission and absorption of infrared radiation
- - - - Pressure = Force / Area
    - - If it is spread over a small area it will result in large pressure
  - - - Pressure is exerted evenly across whole surface of fluid and in all directions
      - Pressure exerted on objects in fluids creates forces against surfaces
      - These forces act 90 degrees to the surface
      - Force from pressure is exerted evenly across whole surface of an object in a liquid in all directions
    - - Depth within fluid
      - Increased density of fluid
    - - Δp = ρgΔh
        
        Δp = change in pressure in pascal
        
        ρ = density of the liquid in kilograms per metre cubed
        
        g = gravitational field strength on Earth in newtons per kilogram
        
        Δh = change in height of the column in metres (m)