Why does water freeze faster than oil?


The freezing of a given substance occurs at a temperature where the liquid form of the substance, releases sufficient heat, making the liquid turn into a solid. The freezing-point of the liquid form of a particular substance is similar to the melting-point of the substance’s solid form, which depends on some factors; such as; the substance’s purity and the pressure that is surrounding it. The water’s freezing point, at one atmosphere pressure, is 0°C, which is equal to 32 ° Fahrenheit, which is also the same as 273.15 Kelvin. And the freezing-point of liquid nitrogen can be given as; -209.89°C, which is equal to -345.8°F, or simply 63.26 Kelvin.

Considering a pure liquid, it should have a definite freezing-point. Similar to sugar solutions, where cooling may lead to super-saturated solutions before the crystallization starts, water could be super-cooled before freezing into ice.

On the other hand, oils, which are lipids in terms of composition, have altered molecular structures which are not fixed like in the case of water. Oils comprise of a large group of compounds which are soluble generally in organic-solvents and on the other hand insoluble in water. In terms of chemical composition, oils are mostly tri-esters of fatty-acids and glycerol. Lipids may either be in liquid or solid at room temperature, which is depended on their chemical structure and also the composition. Despite of the words; “fats”, “lipids” and “oils” being commonly used in reference to lipids, “oils” is commonly  used in reference to lipids that are in liquid form  at room temperature, and on the other hand, “fats” is commonly used in reference to lipids that are in solid form at room temperature. Finally, “Lipids” is used in reference to both oils and fats, as well as other substances which are related. The term “oil” is also commonly used to describe any substance which possesses a greasy feel and is immiscible with water; For instance, cooking oil, essential oil and petroleum.

Oils form a category that is differentiated from other lipids by their physical properties and chemical structure. Some examples of lipids may include; lard, butter/ghee, fish oil, sunflower, coconut, soya bean, olive, sesame, and vegetable oils. Vegetable and Margarine shortening which can be obtained from the above oils, can be used commonly for baking. These lipids can be categorized into two categories; saturated lipids and unsaturated lipids.

Their freezing point is depended on their molecular structures. Margarine oils are mostly solid at the temperature of 32 °C which is equal to 90 °F or simply 305 Kelvin, which helps in that, the margarine doesn’t melt at room temperature and on the other hand, it is required to be completely melted into liquid at 37 °C which is equal to 98 °F or simply 310 Kelvin, so that it can melt completely while in the mouth.

In the process of freezing water, the molecules of water rearrange themselves into some special patterns, which explains why sometimes we can observe clear patterns in the water crystals. In case there is some impurities, like salt, dissolved in the water, then it makes it a little bit harder for the molecules of the water to form proper crystalline patterns. Since the salt molecules are not of the same size or shape as those of the water, they can’t fit exactly into the solidified water crystals, despite of them fitting nicely into the molecular structure of the liquid water. Due to this, it is much hard to freeze/solidify liquids like soda or juice than the plain water – that is, they have to be cooled further before attaining their freezing point. This explains why the impure liquids do not freeze as fast as plain water, a phenomenon which is called; freezing point depression.

Considering both liquids; water and oil, taking into account their respective melting-points, or even taking a fixed temperature below their respective melting-points, the rate with which they will freeze will be depended on their respective latent heats, also known as their enthalpy of fusion. If we take into account a constant room temperature; that will not yield the required results since the temperature has to be reduced to reasonable levels. According to the Newton’s Law of cooling; (freezing rate = d temp / d time), hence the change in temperature will help in controlling the freezing rate. This will also depend on the type of oil. Generally, water has more massive bound neutrons than most of the organic compounds. Scientifically, the more the massive bound neutrons, the lower the zero-point energy compared to the massive bound protons, this can be easily understood or simply clearly explained by the basic quantum mechanics. This means that, their energy can be lost more as the water freezes from liquid into solid, as opposed to the oil. Hence water will freeze faster.

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