The branched structure isomer will require less energy to melt than the straight chain isomer
explanation
Branched structure isomer has weak intermolecular forces of attraction as compared to straight chain isomers. In addition the branched isomer has a low boiling point as compared to straight chain isomers. Since boiling require the of the intermolecular forces tend to have lower boiling point than straight chain
Answer: Among the listed substances 
is the molecular compound.
Explanation:
A chemical compound formed by the chemical combination of two or more non-metals is called a molecular compound or covalent compound.
For example, Xe and Cl are non-metals. The compound formed by them is which is a molecular compound.
A molecular compound is formed by sharing of atoms between the combining atoms.
Whereas NaF, 
and CaO are all ionic compounds as they are formed by chemical combination of a metal and a non-metal.
Thus, we can conclude that among the listed substances is the molecular compound.
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Hydrogen is a non-polar gas with very weak intermolecular forces of attraction. Hydrogen will deviate from the ideal gas behavior at high pressure.
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