Question

The pictures below show the particles of two substances with different energies.



What will happen if the two substances are put into contact in an isolated system?

a
The energy in the system will eventually be destroyed.
b
The energy in the system will eventually increase as energy is created.
c
The energy in the system will transfer from substance B to A until equilibrium is reached.
d
The energy in the system will transfer from substance A to B until equilibrium is reached.

Answer 1

In an isolated system where two substances with different energy levels are brought into contact, the energy will typically transfer from the substance with higher energy to the substance with lower energy until thermal equilibrium is reached.

Assuming substance A has lower energy and substance B has higher energy, the correct answer would be:

**c** The energy in the system will transfer from substance B to A until equilibrium is reached.

If the roles are reversed (substance A has higher energy than substance B), then the answer would be:

**d** The energy in the system will transfer from substance A to B until equilibrium is reached.

Without knowing which substance has the higher energy, one of those two options (c or d) would apply.