Final answer:
A substance in chemistry is matter that has consistent physical and chemical properties throughout, such as aluminum (an element) or water (a compound). Elements are pure substances that can't be chemically broken down, while compounds consist of two or more elements chemically combined.
Step-by-step explanation:
What is a Substance?
In simple terms, a substance in chemistry is a sample of matter that has the exact same physical and chemical properties all the way through. This means it's uniform, or the same everywhere within it, with properties like melting point, color, and boiling point being the same throughout. Think of it like a single recipe that makes one specific dish, no matter where or when you make it.
Chemistry recognizes two main types of substances, which are elements and compounds. An element is like a basic building block—something that can't be broken down into anything simpler through chemical means. Aluminum, the stuff in soda cans, is an example of an element. On the other hand, a compound is made when two or more elements are chemically joined to form a new substance, like water, which combines hydrogen and oxygen.
It's different from a mixture, which is like a salad with different ingredients tossed together but not chemically joined. Each bit of a mixture might taste a little different, but a pure substance is the same through and through.