Final answer:
An example of a chemical change is the burning of a candle, as it converts wax into carbon dioxide and water, indicating new substances with different properties are formed.
Step-by-step explanation:
The example used in class to illustrate a chemical change is a) Burning a candle. This process involves the transformation of candle wax into new substances: carbon dioxide and water vapor, which is a clear indication of a chemical reaction. Similarly, burning natural gas in a furnace causes methane and oxygen to react, forming water and carbon dioxide, another classic example of a chemical change. These processes result in new products with different chemical properties from the original substances.
Chemical changes are distinct from physical changes in that they involve the formation of new substances. For instance, cutting a piece of paper is a physical change, whereas rusting of iron is a chemical change because it results in the formation of a new compound - iron oxide. Chemical changes are typically irreversible without further chemical reactions.