P1A

P1A

1. Facts

   • Heat is a measure of energy (measured in Joules)
   • Heat is measured on an absolute scale (i.e. it starts at 0 – you cannot have -heat)
   • There is no such thing as cold energy, if something is cold it is because it doesn’t have much heat energy.
   • Temperature is a measure of hotness (measured in °C)
   • The hotter something is in comparison to its surroundings, the quicker it will cool down.
   • A thermogram indicates temperature.
   • Heat energy always flows from hotter to cooler bodies.
   • Specific Heat Capacity (c) is the energy needed to raise the temperature of a 1kg block of a material by 1°C.
     • A high specific heat capacity will mean the material takes a lot of energy to heat up, and has to lose a lot of energy to cool down.
   • Specific Latent Heat is the energy needed to change the state of 1kg of a material.
     • A high specific latent heat means it takes a lot of energy to change its state (i.e melt or evaporate).
   • When a material changes state, the temperature does not increase as the energy is used to break intermolecular bonds rather than increasing the kinetic energy of the molecules.
   • The particles in a hot object have more kinetic energy than a cold object.

2. Processes

   • Use specific heat capacity and latent heat equations
     • SHC
       • Energy=Mass x SHC x Temperature Change
         • How much energy is needed to heat 2kg of water from 10C to 100C?
           • 2 x 4200 x 90 = 756000J
     • SLH
       • Energy=Mass x SLH
         • How much energy is needed to melt an ice cube of mass 7g at 0C?
           • 0.007 x 334000J = 2338J
   • Interpret data on rate of cooling
   • Explain how thermograms use colour
     • Images produced by thermal imaging cameras are called thermograms. These cameras detect infrared radiation which is emitted by all objects.
       • The hottest parts of the image are coloured white, yellow or red. The coldest parts are coloured purple, dark blue or black.

Images and files in the map