Solid
substance a has a melting point of 100°c.
liquid substance b has a freezing point of
110°c. for each substance, identify its state
of matter, and describe the motion of its
particles, when the substance is at 115°c.

Both substance A and B will be at liquid state at 115 degree Celsius.

Explanation:

Substance A

Melting point of  substance A is 100 degree Celsius. Thus,   temperature higher than 100 degree will result into liquid substance A. Thus at 115 degree Celsius, substance A is liquid and the particle will be free enough to move and slide over each other.

Substance B

The freezing point of substance B is 110 degree Celsius. This means that for any temperature higher than 110 degree Celsius, substance B will occur in liquid state. The particles of solution B at liquid state will also be free enough to move and slide over each other.