ANS:C - difference in intermolecular forces.

The difference in the properties of a substance in three states of matter depends upon the difference in intermolecular forces. Explanation:

• Intermolecular forces: These forces are the attractions or repulsions between molecules. In solids, molecules are closely packed together, and the intermolecular forces are strong, leading to a fixed shape and volume. In liquids, molecules are still close together, but they are free to move past one another, and the intermolecular forces are weaker than in solids. In gases, molecules are far apart, and the intermolecular forces are very weak, allowing the gas to expand to fill its container completely.

While binding energy of atoms and molecular shape can influence the properties of substances, the primary factor determining the difference in properties among the three states of matter is the strength and nature of intermolecular forces. Therefore, the correct answer is: difference in intermolecular forces.