Ablack powder is added to a clear liquid. fizzing and bubbling occur, and the test tube becomes hot to the touch.

The system shows that a chemical change is happening or a chemical reaction since there is a fizzing, bubbling and giving off of heat to the surroundings that was observed. The fizzing and bubbling signifies that a gas is evolved by the reaction and is escaping the liquid phase. The giving off of heat shows that the reaction is an endothermic reaction where heat is transferred to the surroundings. 

It is called a neutralization reaction