The triple point of any substance is the combination of temperature and pressure at which a substance can exist in all three states – solid, liquid, and gas. Students of class 11 Physics can understand using the examples given in chapter 5. The triple point of water is 273.16 K and the vapor pressure is 611.66 Pascal’s. At this point, water can exist in three states through small changes in pressure and temperature: vapor, liquid, and ice.