P1.2 Changes Of State Flashcards
Specific Heat Capacity
Hint: equation for energy supplied
E = m x c x Δϴ
Energy supplied(J) = mass (kg) x SHC(J/kg oC or K) x temperature change(°C or K)
Temperature change = final - initial
Amount of energy needed to raise the temperature of 1kg of a material by 1K, or 1°C
Type of material
Mass of the material
Temperature rise
Also tells how resistant a material is to temperature change
Oil is added to the thermometer slot in the heater of an experiment setup as oil has lower SHC than air, heats up quicker.
Density
How much mass there is in a certain volume
Equation triangle:
. / M \
/D | V\
Density (kg/m ³) = mass(kg) / volume (m³)
Density of liquids is 1000x greater than gases
Why solids are denser than liquids and gases
More particles in 1cm³ in a solid than 1cm³ of the age substance in the gas state
Mass of solid is greater so its density is also greater
Density of liquids is 1000x greater than density of gases
Temperature
How hot or old something is
Measured with thermometer or temperature sensor
Measured in ° C or kelvin (K)
Difference in temperature of 1 ° Celsius = difference in 1K
Melting or boiling point of a substance would be few cm higher, 5cm higher when reading from a graph.
Difference between temperature and energy
Energy measured in joules (J)
Depends on arrangement of particles and how fast they are moving or vibrating.
Temperature tells about average kinetic energy of the particles.
What stores more energy: Both are 30 ° Celsius:
Cup of water
Swimming pool
Swimming pool - more particles with the same kinetic energy so larger energy store
What happens when you heat things up
Changes energy stored within the system to increase temperature (water heating up)
Change of state (ice melting)
Cause chemical reactions to occur (wood burning in a bonfire)
Particles in solids vibrate faster
Why water is used in a central heating system
Resistant to temperature change
Also means that oceans are less likely to freeze.
Why saucepans are made of materials with low SHC
Need to heat up quickly
Considerations when choosing metal to make a saucepan:
Gold and platinum have very low SHC but very expensive
Some metals are poisonous
What happens when sea evaporates to form water vapour
Energy is transferred from the thermal store of the surroundings to water
Opposite when water vapour condenses
Why there is no temperature rise when you melt or boil a substance
Internal energy is increasing even though the temperature is not
Energy transferred is breaking attractive forces between molecules of the substance
Specific latent heat of fusion (melting)
Specific latent heat of vaporisation
Energy transferred when 1kg of substance changes from solid state to liquid state or liquid state to solid state
SLC of vaporisation = energy transferred when 1kg of a substance changes from liquid to gas state.
Specific latent heat equation
Thermal energy for a change in state(J) = mass(kg) x SLH(J/kg)
Specific latent heat vs specific heat capacity
Both involve energy changes for 1kg of a substance
Latent heat is about change of state but heat capacity is about change of temperature
