Phase Changes Flashcards
State Changes
When a substance changes from a solid to a liquid, or a liquid to a gas, this is called a state change.
During a state change: (1) energy is added to the system, (2) system has an increase in average kinetic energy, (3) system stays the same temperature.
Latent Heat
Latent heat is the energy absorbed or released to change the state of a substance. When a substance goes from a lower energy state to a higher energy state, the latent heat gives the particles in the substance enough energy to move with more freedom, whilst keeping temperature the same. It is a form of energy, measured in joules.
Latent Heat
Latent heat is the energy absorbed or released to change the state of a substance. When a substance goes from a lower energy state to a higher energy state, the latent heat gives the particles in the substance enough energy to move with more freedom, whilst keeping temperature the same. It is a form of energy, measured in joules.
Latent Heat Graphs
On latent heat graphs, a flat graph indicates a phase change. This is because temperature stays the same during the phase change. Positive gradients indicate temperature increase (whilst in the same state - SHC). Solids have the least energy, then liquids, then gases. The total latent heat for a particular state change can be calculated using the length of the horizontal line in terms of the heat added.
Temperature vs Internal Energy during State Change
The temperature during a phase change stays the same, however the internal energy of the particles rises to provide enough energy to ‘break through’ and transform into the next phase. Therefore, the increased energy is not going towards increasing the temp, but rather changing the phase.
A substance is heated with 3.5kJ of energy but does not change temperature. Explain how this is possible.
The substance does not change temperature because it has undergone a phase chnage. During a phase change, energy is added, but the temperature does not increase.
