1, the melting boiling point of homologous metals decreases from top to bottom, and that of homologous nonmetals increases from top to bottom.

2. The melting point of nonmetallic elements in the same family increases from top to bottom, and NH3, H2O and HF containing hydrogen bonds are abnormal.

3. Atomic crystal melting only destroys valence bonds, ionic crystal melting only destroys ionic bonds, and molecular crystal melting only destroys intermolecular forces.

4. The chemical reaction in an open container is an open system. Because the reaction system has both material exchange and energy exchange with the environment.

5. The environment is a part outside the system. Environment usually refers to a limited part of the interaction with the system.