Specific Heat Capacity/ Internal energy and changes of state. Flashcards
What is specific heat capacity?
The amount of energy needed to raise the temperature of 1 kg of a substance by 1° C.
Formula involving Specific Heat Capacity?
E = m × c × θ
E is the energy transferred in joules, J
m is the mass of the substances in kg
c is the specific heat capacity in J / kg °C
θ (‘theta’) is the temperature change in degrees Celsius, °C.
Change in Thermal Energy=Mass x S.H.C x temperature change
How is internal energy Stored?
By the particles that make up a system. The particles vibrate or move around- they have energy in their kinetic energy stores.
What is the internal energy of a system?
The total energy that its particles have in their kinetic and potential energy stores.
What happens when you heat the system?
Energy is transferred to its particles (They gain energy in their kinetic energy stores and move faster), increasing the internal energy. This leads to a change in temperature or a change in state.
When does a change of state occur?
When a substance is heated enough. The particles will have enough energy in their kinetic energy stores to break the bonds holding them together.
The state can also change due to …
cooling. The particles lose energy and form bonds.
A change of state conserves
MASS
A change of state is a PHYSICAL change rather than a chemical change. This means you don’t end up with a new substance. It is the same substance as you started with, just in a different form. The number of PARTICLES doesn’t change - they’re just ARRANGED DIFFERENTLY. This means MASS IS CONSERVED - none of it is lost when the substance changes state.
Is evaporation the same as boiling?
NO. Evaporation only happens at the surface. It can happen at any temperature below the boiling point.
When does boiling happen?
Boiling only happens at one temperature. The boiling point.
Pure substances have…
precise melting and boiling points. (useful for being able to test what a substance actually is as we know a lot of boiling and melting points of substances)
The total energy stored by particles of a substance is called..
the INTERNAL ENERGY.
INTERNAL ENERGY =
KINETIC ENERGY + POTENTIAL ENERGY. (as the temperature increases the internal energy increases).
The potential energy stored in the bonds increases when…
the substance changes state. Eg water from a liquid to a gas (the paricles are further apart)
