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?

Verified step by step guidance

1. Identify the substances in the reaction: H₂O₂ (hydrogen peroxide), H₂ (hydrogen gas), and O₂ (oxygen gas).
2. Recall the definition of a chemical compound: A chemical compound is a substance composed of two or more different elements chemically bonded together in a fixed ratio.
3. Analyze H₂O₂ (hydrogen peroxide): It contains hydrogen (H) and oxygen (O) chemically bonded together, so it is a chemical compound.
4. Recall the definition of an element: An element is a pure substance consisting of only one type of atom, as found on the periodic table.
5. Analyze H₂ (hydrogen gas) and O₂ (oxygen gas): Both consist of only one type of atom (H and O, respectively), so they are elements.

Key Concepts

Chemical Compounds

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

Elements are pure substances that cannot be broken down into simpler substances by chemical means. They are the basic building blocks of matter and are 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

Chemical reactions involve the transformation of reactants into products through the breaking and forming of chemical bonds. In the reaction given, hydrogen peroxide decomposes into water and oxygen, illustrating a chemical change. Understanding the nature of reactants and products is essential for identifying which substances are compounds and which are elements.