Explain why on addition of 1 mol of glucose to 1 litre of water, the boiling point of water increases.

Explain in why on addition of 1 moe of NaCl to 1L of water, the boiling point of water increases, while addition of 1 mole of methyl alcohol to 1 L of water decreases its boilbing point .

The boiling point of heavy water is

Why does water have high boiling point?