Question

which statement best explains why knowing the melting and boiling points of the steel wool and the iron oxide is important for allowing the students to prove that a chemical change occurred to the steel wool?
a. after a chemical change, the melting and boiling point of all products are different from each other.
b. after a chemical change, the melting point and boiling point of all metals are the same.
c. after a chemical change, the melting point and boiling point should be different for products and reactants.
d. after a chemical change, the melting point and boiling point should remain the same for products and reactants.

Explanation:

A chemical change results in the formation of new substances. Melting and boiling points are physical properties that are characteristic of a substance. If a chemical change occurs, the new substance (product) will have different properties than the original substance (reactant). So, comparing the melting and boiling points of reactants (steel wool) and products (iron oxide) helps prove a chemical change. Option C correctly states that after a chemical change, the melting and boiling point should be different for products and reactants. Option A is incorrect as it says "all products are different from each other" which is not relevant to proving a chemical change between reactant and product. Option B is wrong as metals don't have same melting and boiling points after a chemical change. Option D is incorrect because in a chemical change, properties of products and reactants change.

Answer:

C. After a chemical change, the melting point and boiling point should be different for products and reactants.