Ben and Jerry were testing powders in science lab. First they put the powder in a zip lock bag. Next they added some water. The
powder fizzed and bubbled; soon it disappeared. When the bubbling stopped the bag contained a clear liquid and a lot of gas. What is the MOST OBVIOUS sign of a chemical change in this reaction. A) A gas was produced. B) The powder mixed with the water. C) There was a change in temperature. D) The powder dissolved in the water.
In a chemical change there is always a change in the chemical composition. When reactant reacts with one another new products are formed, the products have a different chemical composition than the reactants. Option A is correct as gases have evolved as a result of chemical change.
Option B and D are physical changes therefore incorrect. When matter dissolves in water or mixes with another substance there is no change in the chemical composition of the said matter.
Option C is incorrect as change in temperature is a change in the kinetic energy of matter and is not a chemical change.
