//=================================================================================================
public abstract class H2O {
//-------------------------------------------------------------------------------------------------
    protected static final double LITERS_OF_WATER_PER_MOLE = 0.018;

    protected double numberOfMoles;
//-------------------------------------------------------------------------------------------------
    public H2O(double numberOfMoles) {

        this.numberOfMoles = numberOfMoles;
    }
//-------------------------------------------------------------------------------------------------
    public String toString() {

        return(numberOfMoles + " H2O moles");
    }
//-------------------------------------------------------------------------------------------------
    public abstract double computeVolume();
//-------------------------------------------------------------------------------------------------
}
//=================================================================================================