Changes of state

• When a substance changes state, mass is conserved.
• A solid changing to a gas is called subliming.
• When a gas turns into a liquid, it is called condensation.
• Changes of state are physical changes that differ from chemical changes because the material recovers its original properties if the change is reversed.
• Internal energy is energy stored inside a system by particles (atoms and molecules) that make up the system.
• Internal energy is the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system.
• Heating changes the energy stored within the system by increasing the energy of the particles that make up the system. This either raises the temperature of the system or produces a change of state.
• If the temperature of the system increases, the increase in temperature depends on the mass of the substance heated, the type of material and the energy input to the system.
• to calculate the change in thermal energy, use $∆ E =$$m c ∆ θ$
• The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.
• The specific latent heat of a substance is the amount of energy required to change the state of one kilogram of the substance with no change in temperature.
• When a change of state occurs, the energy supplied changes the energy stored (internal energy) but not the temperature.
• to calculate the energy needed for a change of state, use $E =$$m L$
• The molecules of a gas are in constant random motion
• The temperature of the gas is related to the average kinetic energy of the molecules.
• Changing the temperature of a gas, held at constant volume, changes the pressure exerted by the gas.