Classify the below substances based on their natural physical state.
Water, Mercury, Copper, Oxygen, Nitrogen, Wood
Solid - Copper, Wood
Liquid - Water, Mercury
Gas - Oxygen, Nitrogen
### Instruction: Classify the below substances based on their natural physical state.
Water, Mercury, Copper, Oxygen, Nitrogen, Wood
### Context: 
### Answer: Solid - Copper, Wood
Liquid - Water, Mercury
Gas - Oxygen, Nitrogen</s>