The correct statement among the following is:

1. The presence of reacting species in a covered beaker is an example of an open system.
2. There is an exchange of energy as well as matter between the system and the surroundings in a closed system.
3. The presence of reactants in a closed vessel made up of copper is an example of a closed system.
4. The presence of reactants in a thermos flask or any other closed insulated vessel is an example of a closed system.

Hint: In a closed system, only an exchange of energy is taking place
 
For a closed vessel made of copper, no matter can exchange between the system and the surroundings but energy exchange can occur through its walls. Copper is a good conductor of heat. Thus, in a copper vessel, only heat can exchange but matter does not exchange.