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Butter is solid at room temperature because it’s a saturated fat. Unsaturated fats (such as canola oil, olive oil, almond oil) are liquid at room temperature.
Ghee is a natural dairy product made by heating butter. It contains both unsaturated and saturated fats along with milk protein and some water.
Intermolecular Forces
Intermolecular forces are weaker than intramolecular forces but are important in determining a molecule’s physical properties. They can determine a molecule’s boiling point, melting point, density, and enthalpies of fusion and vaporization.
The simplest way to understand intermolecular forces is that they’re the result of atoms sharing valence electrons. When the sharing is equal, it’s called a non-polar bond; when one atom has more electronegativity than the other, it’s called a polar bond.
When two fatty acids share electrons, they form a covalent bond that’s strong enough to hold a molecule together. Unsaturated fatty acids don’t contain double bonds, so they have weaker intermolecular forces than saturated fats.
Saturated Fatty Acids
Saturated fats are solid at room temperature and are found in foods such as butter, palm and coconut oil, cheese, red meat, and processed foods. These fats are unhealthy because they increase cholesterol in your arteries (blood vessels) and may cause heart disease or stroke.
In contrast, unsaturated fats are liquid at room temperature and are found in olive, canola, corn, soybean, safflower and sesame oils. They are also in fish and nuts.
Unlike saturated fats, unsaturated fats do not have double bonds in their fatty acid tails. This allows the fats to be stacked more easily on top of each other and increases Van der Waals interaction.
This makes it easier for the molecules to break apart at the solid-liquid transition. Because it requires more energy to break the bonds between the fatty acids, unsaturated fats melt at a lower temperature than saturated fats. However, there are some exceptions to this rule. Including more omega-3 and omega-6 fatty acids in your diet can reduce heart disease risk.
Hydrogenated Fatty Acids
Butter is solid at room temperature because it is mostly saturated fat. Saturated fatty acids are not double-bonded like unsaturated ones, so they have a higher melting point.
Saturated fatty acids also have a tendency to stack up in an orderly way. This means that they are held together by relatively weak Van der Waals forces. As the temperature increases, these bonds break and the fatty acids become liquid.
While butter is a saturated fat, it does not contain all of the saturated fatty acids that can increase cholesterol levels in our bodies. It contains stearic acid and some short chain fatty acids, which have little effect on cholesterol levels or a lowering effect.
Hydrocarbon Chains
In order for a fat to be solid at room temperature it must have a straight line of carbon atoms that can be stacked together tightly. This is known as a saturated fatty acid chain because each of the carbon atoms has a hydrogen atom attached to it.
A trans fatty acid, on the other hand, has hydrogen atoms attached on opposite sides of the carbon chain. This makes it difficult for the carbon atoms to be aligned together like in a cis fatty acid.
To make an oil semi-solid and of a consistency desired for many processed foods, the double bonds in the hydrocarbon chain are artificially broken and hydrogens added (through a process called hydrogenation). The result is that the carbon chain becomes less twisted, increases its melting point, and reduces its likelihood of being attacked by oxygen so that it remains fresh longer.
Butter, a type of animal fat, is solid at room temperature because the straight lines of carbon atoms in its fatty acid chains can easily be stacked up and formed into a solid block or fat crystal. This is different from plant oils, such as canola oil, which has unsaturated fatty acids that have double bonding creating kinks in the chain.