Describe the difference between a positive and a negative acceleration

If an object is slowing down, then its acceleration is in the opposite direction of its motion. ... Thus, this object has a positive acceleration. In Example B, the object is moving in the negative direction (i.e., has a negative velocity) and is slowing down. hope it helps

A compound is always homogeneous in nature. 

The constituents cannot be separated by simple physical processes.

The formation of a compound is sometimes accompanied by the evolution of energy in the form of heat or light.