thermal properties of matter

define internal energy

the sum of the kinetic energy due to random motion of particles and potential energy due to forces of attraction between the particles

internal potential vs internal

internal is change in temp. potential is change in state ONLYY

define heat capacity

heat capacity, C, is the amount of heat required to raise the temp of a substance by 1K pr 1C

heat capacity formula

Q = C(change in temp.) depends on mass and material

define specific heat capacity

The amount of heat needed to raise the temperature of 1g (or unit mass) of substance by 1K or 1C

formula of specific heat capacity

change in thermal energy = mass x SHC x temperature change

Q = mc(change in temp.)

what is melting and solidification?

melting is chg frm solid to liquid when energy is transferred to the substance (pure substance melting constant temp!) solidification is just the opp and its js melting (energy transferred out)

boiling and condensation

changes between liquid and gas when energy is transferred to the substance. the reverse is just condensation, energy is transferred out

What is latent heat? (hidden heat)

Latent hear is the energy absored or released to change the state of a substance at constant temp

latent heat in terms of behaviour of particles

energy supplied is used to do work against the forces of attraction bewteen the particles/ energy released to the surroundings causes the forces of attraction to reform around the particles

The particles now have a wider/smaller range of movement and the average distance of the particles increases/decreases. this increases the internal potential energy of the substance whereas the internal kinetic energy remains constant

define latent heat of fusion

The quantity of heat energy required/released to convert a substance of solid to liquid without any temperature change.

define specific latent heat of fusion

The quantity of heat energy required/released to convert a unit mass of substance of solid to liquid without any temperature change.

formula for specific latent heat of fusion/vapourisation

Lf = mlf/Lv = mlv OR Q = m*lf/lv

define evaporation

The change of a substance from a liquid to a gas without boiling

how does evaporation occur

The particles in a liquid are always moving randomly at different speeds.

Particles at the surface of the liquid can escape into the atmosphere if they have sufficient kinetic energy to overcome attractive forces of other liquid particles and do work against atmosphere

less energetic particles are left behind and so the temp decrease

factors affecting rate of evaporation

temperature, surface area, humidity, windspeed, pressure, nature of the liquid