thermal properties of matter Flashcards
(24 cards)
define heat capacity
the amount of heat required to raise the temperature of the object by 1K or 1°C
SI unit for heat capacity
J/K
formula for heat capacity
C = Q (absorbed or released heat)/x (change in temp)
define specific heat capacity
the amount of heat required to raise the temperature of 1kg of the object by 1K or 1°C
SI unit for specific heat capacity
J kg-¹K-¹
OR
J (kg/K)
formula for specific heat capacity
C = Q (absorbed or released heat)/ mass × x (change in temp)
define internal energy
total amount of kinetic and potential energy the particles of an object possess
explain kinetic energy
KE is due to the motion of particles and is directly related to temperature
explain potential energy
PE is due to the stretching and compression of intermolecular bonds as the particles move.
PE is dependent on forces between particles and how far apart they are.
define melting
melting is a process in which a substance changes in state from solid to liquid, without a change in temperature
what is latent heat of fusion
the thermal energy absorbed during melting process/ the thermal energy released during solidification
explain the energy transfer during melting
when ice begins to melt, thermal energy is absorbed to break the bonds between the particles of solid ice.
only the total internal potential energy increases, and kinetic energy of particles remains the same, thus temperature does not change during melting.
define solidification
solidification is a process in which a substance changes its state from liquid to solid, without a change in temperature.
explain the energy transfer during solidification
when liquid freezes, strong bonds are formed when particles move closer together.
only the total internal potential energy increases, and kinetic energy of particles remains the same, thus temperature does not change during melting.
define boiling
boiling is the process in which a substance changes from the liquid state to the gaseous state, without a change in temperature
explain boiling in terms of molecules
during boiling thermal energy is used to break the bonds between water molecules, and to provide energy for the molecules to push back on the surrounds to escape into the air.
define condensation
condensation is the change of state from vapour to liquid, without a change in temperature
explain condensation in terms of molecules
at the condensation point, the substance releases thermal energy as bonds are formed between the particles.
when steam condenses, it releases latent heat of vaporisation
define latent heat of fusion/vaporisation
it is the amount of thermal energy required to change a substance from solid to a liquid / liquid to gaseous, without a change in temperature
define specific latent heat of fusion
it is the amount of thermal energy required to change unit mass of the substance from solid to a liquid / liquid to gaseous, without a change in temperature
formula for specific latent heat of fusion/vaporisation
lf / lv = Q (amt of heat) / m (mass)
SI unit for specific latent heat of fusion/vapourisation
J/kg
explain evaporation
evaporation occurs when a liquid changes in state to a gas, below its boiling point
- molecules are in continuous, random motion at different speeds
- more energetic molecules have the energy to overcome attractive forces due to other molecules and escape from the surface into the atmosphere
- less energetic molecules are left behind and the average KE of the molecules decrease, so the temperature decreases
list factors that affect the rate of evaporation
temperature ↑↓
surface area
humidity ↑↓
boiling point of liquid
pressure
movement of air
