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    "# 4.5 – Phase Diagrams\n",
    "\n",
    "---"
   ]
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    "## 4.5.0 – Learning Objectives\n",
    "\n",
    "By the end of this section you should be able to:\n",
    "\n",
    "1. Understand what each line in a phase diagram represent.\n",
    "2. Understand what is in each region of a phase diagram.\n",
    "3. Understand what important points are on the phase diagram.\n",
    "4. Understand what the difference is between a vapour and gas.\n",
    "\n",
    "---"
   ]
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    "## 4.5.1 – Introduction\n",
    "\n",
    "**Phase diagrams** are used to show all the phases of a substance at different pressures and temperatures. Each line represents phase equilibrium or boundaries.\n",
    "\n",
    "---"
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    "## 4.5.2 – Diagram\n",
    "\n",
    "Shown bellow is a typical phase diagram.\n",
    "\n",
    "![](../figures/Module-4/Phase_Diagram1.png)\n",
    "\n",
    "Attribution: [[::User:Matthieumarechal|Matthieumarechal]] [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons\n",
    "\n",
    "The **red line** represents the boundary between a solid and a vapour. In this area, solid will directly turn to a vapour or a vapour will directly turn into a solid such as dry ice and $CO_2$. The **dotted green line** represents the boundary between a liquid and a solid for polar fluids such as water. Since ice is less dense than liquid water, it causes the dotted line to skew to the left. The **solid green line** represents the same thing as the **dotted green line** except for non-polar fluids. Finally, the **blue line** represents the boundary between a liquid and a vapour.\n",
    "\n",
    "Two main points of interest are the **triple point** and the **critical point**. The triple point is the point at which all three phases coexist at a certain pressure and temperature. The critical point is the point at which if you increase the pressure or temperature, a gas becomes indistinguishable from the liquid. The phase in this region is called a **supercritical fluid**.\n",
    "\n",
    "Another example of a phase diagram is shown below. This is the phase diagram of water.\n",
    "\n",
    "![](../figures/Module-4/Phase_diagram_of_water1.png)\n",
    "\n",
    "Attribution: By Cmglee (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons\n",
    "\n",
    "---"
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    "## 4.5.3 – Difference Between Vapour and Gas\n",
    "\n",
    "A substance is considered a **gas** when its temperature is **higher** than the critical temperature and below the critical pressure. A gas can not become a liquid by just increasing the pressure, you must also lower the temperature. \n",
    "\n",
    "A substance is considered a **vapour** when its temperature is **lower** than the critical temperature and below the critical pressure. A vapour can become a liquid by just increasing the pressure."
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    "## 4.5.4 – Phase diagrams for ternary systems \n",
    "\n",
    "Partially miscible systems with 3 components can be represented in a ternary phase diagram. It's actually shaped like an equililateral triangle:\n",
    "\n"
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