Once a chemical bond is formed, the atoms are rearranged to form a stronger bond, affecting the hardness, malleability, etc. The stronger the bond, the easier a substance will break, or, if its a liquid, it will resist seperation.
Answer:

Explanation:
Hello,
In this case, for latent heat (phase change) we need to consider the enthalpy associated with the involved process, here, melting or fusion; thus, the enthalpy of fusion of copper is 13.2 kJ/mol, therefore, the heat is computed as:

Nevertheless, since the given enthalpy is per mole of copper, we need to use its atomic mass to perform the correct calculation as follows:

Which is positive as it needs to be supplied to the system.
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Quantum Mechanical model (as per my knowledge)
Answer:A double convalescent bond is where two pairs of electrons are shared between the atoms rather than just one pair. Two oxygen atoms can both achieve stable structures by sharing two pairs of electrons as in the diagram.
Explanation:
You can tell the difference by How shiny it is and by how heavy it is