Final answer:
The correct statements are III and IV, indicating that chemical formulas and the number of each type of atom they contain are used to identify substances. Subscripts are part of the chemical formula and should not be changed when balancing chemical equations.
Step-by-step explanation:
The correct statement is B) III and IV: Chemical formulas are used to identify substances, and the elements and the number of atoms of each element present in a chemical formula are used to identify substances. Subscripts in a chemical formula represent the number of atoms of the element that are present in one molecule of a compound. For example, the chemical formula for water is H2O, which means there are two hydrogen atoms and one oxygen atom in each molecule of water.
Coefficients and subscripts are two different components of chemical equations. While subscripts are part of the chemical formulas and indicate the number of atoms of an element in a molecule, coefficients are placed in front of the formulas to show how many molecules participate in the reaction. It's important to note that subscripts should not be changed when balancing chemical equations as this would change the compound itself, transforming it into a different substance with different chemical properties.
An example of a molecular formula representing a different chemical substance is carbon dioxide, CO2, which has one carbon atom and two oxygen atoms per molecule. Chemical formulas provide valuable information regarding the composition of chemical compounds and are crucial for understanding chemical reactions and substances.