Final answer:
Two examples of chemical reactions are the reaction between copper (II) sulfate and iron, which causes a color change, and the reaction between acetic acid and sodium bicarbonate, which produces carbon dioxide gas, indicating gas evolution.
Step-by-step explanation:
Chemical reactions can be identified by various indicators, such as a change in color or the evolution of gas. Here are examples for each situation:
- Color Change: The reaction between copper (II) sulfate and iron produces iron (II) sulfate and copper. The greenish color of copper (II) sulfate changes to the light green color of iron (II) sulfate, and reddish-brown copper metal is formed, indicating a color change.
- Gas Evolution: When acetic acid reacts with sodium bicarbonate, carbon dioxide gas is produced along with water and sodium acetate. The evolution of carbon dioxide is observed as bubbling, indicating a gas is evolved.
These two examples demonstrate physical observations that suggest a chemical reaction has taken place, either through a change in the substance's color or the production of a gas at room temperature.