question: A sample of matter that has the same physical and chemical properties throughout itself is known as what?
distractor3: molecule
distractor1: antimatter
distractor2: essence
correct_answer: substance
support: A sample of matter that has the same physical and chemical properties throughout is called a substance. Sometimes the phrase pure substance is used, but the word pure isn’t needed. The definition of the term substance is an example of how chemistry has a specific definition for a word that is used in everyday language with a different, vaguer definition. Here, we will use the term substance with its strict chemical definition. Chemistry recognizes two different types of substances: elements and compounds. An element is the simplest type of chemical substance; it cannot be broken down into simpler chemical substances by ordinary chemical means. There are about 115 elements known to science, of which 80 are stable. (The other elements are radioactive, a condition we will consider in Chapter 15 "Nuclear Chemistry". ) Each element has its own unique set of physical and chemical properties. Examples of elements include iron, carbon, and gold.