Final answer:
Iron chain rusting, a piece of paper burning, and a peach spoiling are all examples of chemical changes, as new substances are formed. Melting a glue stick with a glue gun is a physical change since only the state of the substance changes.
Step-by-step explanation
When we look at changes in substances, we categorize them as either physical changes or chemical changes. A physical change involves a change in physical properties without altering the chemical composition of the substance. A chemical change, on the other hand, results in the formation of one or more new substances with different properties.
- Iron chain rusting over a long period of time is a chemical change. Rusting occurs when iron reacts with oxygen in the air, forming iron oxide, a new substance.
- When a piece of paper burns, it undergoes a chemical change. Burning results in the formation of new substances, such as carbon dioxide and water vapor, along with the release of energy as heat and light.
- A peach spoils by bacteria and rots, which is a chemical change caused by the action of microorganisms that break down the peach's compounds, leading to the creation of new substances.
- When a glue gun melts a glue stick, it is a physical change because the melting process only alters the state of the glue from solid to liquid, without changing its chemical composition.