Hydrogen peroxide, often used in solutions to cleanse cuts and scrapes, breaks down to yield water and oxygen:Hydrogen peroxide, H₂O₂ (aq) → Hydrogen, H₂ (g) + Oxygen, O₂ (g)b. Which of the substances are chemical compounds, and which are elements?

Chemical compounds are substances formed when two or more elements chemically bond together in fixed proportions. In the given reaction, hydrogen peroxide (H₂O₂) is a chemical compound because it consists of hydrogen and oxygen atoms bonded together. Compounds have distinct properties that differ from the individual elements that compose them.

Elements are pure substances that cannot be broken down into simpler substances by chemical means. They are the fundamental building blocks of matter, represented on the periodic table. In the reaction provided, hydrogen (H₂) and oxygen (O₂) are elements, as they consist of only one type of atom and cannot be decomposed into simpler substances.

Chemical reactions involve the transformation of reactants into products through the breaking and forming of chemical bonds. In the reaction of hydrogen peroxide breaking down, it decomposes into water and oxygen, illustrating how compounds can change into elements and other compounds. Understanding this process is essential for identifying the nature of substances involved in a reaction.