Final answer:
From lowest to highest melting point, the order is C2H4, N2H4, and then CaCl2, based on the strength of intermolecular forces, which are London dispersion forces, hydrogen bonding, and ionic interactions, respectively.
Step-by-step explanation:
To order the molecules N2H4 (hydrazine), CaCl2 (calcium chloride), and C2H4 (ethylene) from lowest to highest melting point, we need to consider the types of intermolecular forces present in these compounds. N2H4 is a molecule that exhibits hydrogen bonding. C2H4 is a nonpolar molecule with only London dispersion forces. CaCl2, being an ionic compound, exhibits strong ionic interactions. Generally, ionic interactions are the strongest, followed by hydrogen bonding, and then London dispersion forces.
Therefore, the order from lowest to highest melting point is:
- C2H4 (London dispersion forces, nonpolar molecule)
- N2H4 (Hydrogen bonding, polar molecule)
- CaCl2 (Ionic interactions)