P3 : Internal Energy

Question 1

Particles

Answer 1

Particles in solids, liquids and gases all have kinetic energy
Particles also have potential energy (intermolecular forces and chemical bonds)

Question 2

Internal Energy

Answer 2

Internal energy is the energy stored in a system by the particles
It’s the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system

Question 3

Changes of state (freezing and condensation)

Answer 3

If we cool the gas back down again, then we reduce the internal energy, at some point the gas turns back into a liquid (condensation)
If we cool the liquid down further, then we reduce the internal energy even more. Eventually the liquid turns into a solid (freezing)

Question 4

Sublimation

Answer 4

Sometimes a solid can turn directly into a gas, scientists call this sublimation

Question 5

Why can a substance return to it’s original form

Answer 5

Changes of state are not chemical changes if we reverse the change the material recovers its original properties

Question 6

Evaporation

Answer 6

Evaporation is when a liquid turns to a gas but only on the surface of a liquid
In this case, only the particles on the surface have enough energy to turn into a gas