<P> An open water cooling system makes use of evaporative cooling, lowering the temperature of the remaining (unevaporated) water . This method was common in early internal combustion engines, until scale buildup was observed from dissolved salts and minerals in the water . Modern open cooling systems continuously waste a fraction of recirculating water as blowdown to remove dissolved solids at concentrations low enough to prevent scale formation . Some open systems use inexpensive tap water, but this requires higher blowdown rates than deionized or distilled water . Purified water systems still require blowdown to remove accumulation of byproducts of chemical treatment to prevent corrosion and biofouling . </P> <P> Modern automotive cooling systems are slightly pressurized, often to 15 psi (103 kPa). This raises the boiling - point of the coolant and reduces evaporation . </P> <P> The use of water cooling carries the risk of damage from freezing . Automotive and many other engine cooling applications require the use of a water and antifreeze mixture to lower the freezing point to a temperature unlikely to be experienced . Antifreeze also inhibits corrosion from dissimilar metals and can increase the boiling point, allowing a wider range of water cooling temperatures . Its distinctive odor also alerts operators to cooling system leaks and problems that would go unnoticed in a water - only cooling system . The heated coolant mixture can also be used to warm the air inside the car by means of the heater core . </P> <P> Other less common chemical additives are products to reduce surface tension . These additives are meant to increase the efficiency of automotive cooling systems . Such products are used to enhance the cooling of underperforming or undersized cooling systems or in racing where the weight of a larger cooling system could be a disadvantage . </P>

Explain state of water changes on heating or cooling with neat sketch