* Physical Change: A change in the form or appearance of a substance, but not its chemical composition.
* Chemical Change: A change that results in the formation of new substances with different chemical properties.
When you mix powdered zinc and sulfur at room temperature, you are simply creating a mixture. The individual particles of zinc and sulfur remain unchanged. They haven't reacted to form a new compound.
Here's what happens when you apply heat:
* Chemical Change: When you heat the mixture of zinc and sulfur, they undergo a vigorous reaction, releasing heat and light. This reaction forms zinc sulfide (ZnS), a new compound with different properties than either zinc or sulfur. This is a clear indication of a chemical change.
In short: Mixing zinc and sulfur at room temperature is a physical change, but heating the mixture causes a chemical change, resulting in the formation of zinc sulfide.
