Introduction:
The cells of cork have unique properties that make them highly resistant to gases and water. This is due to the presence of a chemical called suberin in their cell walls. Suberin is responsible for making the cork cells impervious to these substances.

Explanation:

1. Cork cells:
Cork is a type of tissue derived from the bark of certain trees, such as oak. The cells that make up cork tissue are dead at maturity. These cells are arranged in a compact and uniform manner, forming a protective layer.

2. Chemical in cork cell walls:
The chemical present in the cell walls of cork cells is suberin. Suberin is a complex lipid polymer that is highly hydrophobic, meaning it repels water. It is also impermeable to gases. These properties make suberin an excellent barrier against the entry of water and gases into the cork cells.

3. Impervious to gases:
The presence of suberin in the cell walls of cork cells prevents the diffusion of gases through them. Suberin forms a barrier that blocks the passage of gases, making the cork cells impermeable to gases.

4. Impervious to water:
Suberin also plays a crucial role in making the cork cells impervious to water. The hydrophobic nature of suberin repels water molecules, preventing them from entering the cells. This property is essential for the survival of plants that have cork tissue as it helps to prevent water loss and protect the inner tissues from excess moisture.

Conclusion:
In conclusion, the chemical in the walls of cork cells that makes them impervious to gases and water is suberin. Suberin acts as a barrier, preventing the diffusion of gases and repelling water molecules. These properties are essential for the protective function of cork tissue in plants.