In a chemical reaction, which aspect of the reactants changes?(1 point) A. atoms B. mass C. nuclei D. total mass
The correct answer and explanation is:
The correct answer is A. atoms
Explanation:
In a chemical reaction, the fundamental change that occurs to the reactants involves the atoms they are composed of. While the atoms themselves do not change their identity (e.g., an oxygen atom remains an oxygen atom, a carbon atom remains a carbon atom), their arrangement and the way they are bonded to each other are drastically altered.
Chemical reactions are essentially processes where existing chemical bonds within the reactant molecules are broken, and new chemical bonds are formed to create the product molecules. This breaking and forming of bonds results in a rearrangement of the atoms that were originally making up the reactants. For instance, in the reaction between hydrogen gas (H₂) and oxygen gas (O₂) to form water (H₂O), the bonds between hydrogen atoms in H₂ molecules and between oxygen atoms in O₂ molecules are broken, and new bonds are formed between hydrogen and oxygen atoms to create H₂O molecules. The hydrogen and oxygen atoms, the fundamental building blocks, have changed their connectivity and arrangement.
Let’s look at why the other options are incorrect:
- B. mass: The mass of the individual reactant substances changes as they are consumed during the reaction. However, the mass of the individual atoms themselves does not change in a chemical reaction (protons and neutrons are unaffected). Also, the word “mass” alone can be ambiguous.
- C. nuclei: The nuclei of atoms (containing protons and neutrons) are not changed in a chemical reaction. Chemical reactions only involve interactions between the electrons surrounding the nucleus, specifically the valence electrons that form chemical bonds. Changes to the nucleus occur only in nuclear reactions (like radioactive decay, fission, or fusion).
- D. total mass: According to the Law of Conservation of Mass, the total mass of all substances involved in a chemical reaction remains constant. The total mass of the reactants before the reaction is equal to the total mass of the products after the reaction.
Therefore, the most accurate description of what changes about the reactants at the atomic level during a chemical reaction is the arrangement and bonding of their constituent atoms.