gassy.cs

using System;
using System.Linq;
using System.Collections.Generic;

public static class GasConstants
{
    const float OneAtmosphere = 101.325; // kPa
    const float IdealGasEquation = 8.31; // kPa*L/(K*mol)
    const float TemperatureCosmicMicrowaveBackround = 2.7; // K
}

public sealed class GasType
{
    public string Name { get; private set; }
    public string ShortName { get; private set; }
    public float SpecificHeat { get; private set; }

    private GasType(string name, string shortName, float specificHeat)
    {
        Name = name;
        ShortName = shortName;
        SpecificHeat = specificHeat;
    }

    public static GasType Oxygen = new GasType("oxygen", "O2", 20);
    public static GasType Nitrogen = new GasType("nitrogen", "N", 20);
    public static GasType Plasma = new GasType("plasma", "Pl", 300);
    public static GasType NitrousOxide = new GasType("nitrous oxide", "N2O", 40);
    public static GasType CarbonDioxide = new GasType("carbon dioxide", "CO2", 30);
}

public class GasMixture
{
    private Dictionary<GasType, float> moles = new Dictionary<GasType, float>();
    private float temperature = GasConstants.TemperatureCosmicMicrowaveBackround;

    // Moles
    public float this[GasType type] {
        get {
            if (moles.ContainsKey(type))
                return moles[type];
            else
                return 0;
        }
        set
        {
            if (value <= float.Epsilon)
                moles.Remove(type);
            else
                moles[type] = value;
        }
    }

    // Returns in K
    public float Temperature {
        get { return temperature; }
        set { temperature = Math.Max(value, GasConstants.TemperatureCosmicMicrowaveBackround); }
    }

    // Returns in kPa, volume in L
    public float Pressure(float volume)
    {
        return moles.Values.Sum() * GasConstants.IdealGasEquation * temperature / volume;
    }

    public float HeatCapacity()
    {
        return moles.Sum(g => g.Value * g.Key.SpecificHeat);
    }

    //public void AddGas(GasMixture otherMixture) { ... }

    public void MoveGas(GasMixture otherMixture, float percentage) { ... }
}