which of these has the highest melting point, magnesium-oxide, 1-propanol, methane

magnesium oxide, undoubtedly. It is an ionic solid, the others are organic. CH4 is a gas, propanol is a liquid.

Among the given substances, magnesium oxide (MgO) has the highest melting point.

To determine which substance has the highest melting point among magnesium oxide, 1-propanol, and methane, we need to compare their molecular structures and intermolecular forces.

1. Magnesium oxide (MgO): It is an ionic compound composed of magnesium cations (Mg^2+) and oxide anions (O^2-). The presence of strong ionic bonds between the positively charged metal cations and negatively charged oxide anions leads to a high melting point for ionic compounds.

2. 1-Propanol (C3H8O): It is an organic compound belonging to the alcohol group. It consists of a three-carbon chain (propane) with a hydroxyl group (OH) attached to one end. 1-Propanol molecules are held together by intermolecular forces such as hydrogen bonding. Hydrogen bonding is a relatively strong intermolecular force that increases the melting point compared to substances without hydrogen bonding.

3. Methane (CH4): It is a simple hydrocarbon consisting of one carbon atom bonded to four hydrogen atoms. Methane molecules are held together by weak van der Waals forces, specifically London dispersion forces. These forces are relatively weaker than ionic or hydrogen bonds.

Therefore, considering the above information, magnesium oxide is expected to have the highest melting point due to the presence of strong ionic bonds. 1-Propanol with hydrogen bonding will have a higher melting point than methane, which only has weak van der Waals forces.