Answer is:
It is likely soluble in water.
It will likely light up a bulb in a conductivity apparatus (CaO(l)).
It will likely have a high melting point.
1) Calcium oxide (CaO) has ionic bonds between calcium cations (Ca²⁺) and oxygen anions (O²⁻). It reacts with water and form calcium hydroxide:
CaO(s) + H₂O(l) → Ca(OH)₂(aq).
2) Ionic solid calcium oxide dissolved in water conduct electricty due to the dissociation Ca(OH)₂(aq) → Ca²⁺(aq) + 2OH⁻(aq).
3) Because it has strong ionic bonds, it has high melting point (around 2600°C).
