Does his model correctly show why the properties of the ending substances are different from the properties of the starting substances? Describe what could be correct or incorrect about his model.

Samira's model is incorrect because not all atoms are accounted for

Explanation:

The image of Samira's model has been attached to this answer to enhance the explanation.

What is depicted in that model is rightly regarded as a chemical change. In a chemical change atoms of substances are rearranged as new substances are formed.

However, all atoms in the products must also be found in at least one of the reactants. In this case we have an atom in one of the products that is not accounted for. Hence the model is incorrect.

- lead + phosphoric acid = hydrogen + lead(ii) phosphate