When mixing oil and water, you’d think they’d just stay separate and not mix. But put a drop of one on top of the other, and voila! They combine to make something new, called “emulsions.” These strange hybrid liquids are ubiquitous in nature (e.g. the human skin) and our technology (e.g. lotion, mayonnaise).
Surprisingly, many common household liquids such as salad dressing mix also have an emulsifying agent that helps them blend oil and water so well together. Do you ever wonder why some things won’t mix?
Chemical properties explain why we find particular substances repulsive or delicious, helpful or harmful to our health, and difficult or easy to mix with other substances.
What Happens When Oil Mixed With Water?
In most cases, two or more liquids that naturally repel each other will create an emulsion. This happens when droplets of one liquid are suspended in another, creating a three-phase system: two immiscible liquids and an emulsion.
In an emulsion, the droplets of one liquid (the “dispersing phase”) are suspended in another liquid (the “continuous phase”). When you mix oil and water, the “continuous phase” is water, and the “dispersing phase” is oil.
You can see a wet/dry mixture of ingredients by using a laser layer graph like the one shown below. The property we use to measure this is called “viscosity.” This is a fancy word for the “thickness” or “gooeyness” of a liquid.
The viscosity of a thick liquid like honey is higher than that of a thin liquid like water. When you mix oils and water together, their viscosities change.
The water becomes thicker, and the oil becomes thinner. The “thickness” of the whole mixture is somewhere in the middle.
Why Do Oils and Waters Want to Stay Separate?
If you mix oil and water together, they will only remain mixed while you are actively shaking or stirring them. Once you stop agitating the liquids, they will naturally separate into their individual components. This happens because oils and water have different densities and chemical properties.
Oils are less dense than water, so they naturally float on top of it. Water is a polar molecule, meaning that its molecules have a positive side and a negative side. This gives water the ability to dissolve other polar molecules, but not oil molecules. Oil molecules are nonpolar, so they repel each other and don’t mix with water.
Oil molecules, for example, are very small and “light”, and therefore easily float to the top of the water. On the other hand, water molecules are heavy and “sink” to the bottom of the oil. This happens because of the chemical properties of oil and water that make them repel each other.
People often combine oils and water for cooking, to create sauces, creamy salad dressings, etc. But for mixing, we need to break through the water/oil barrier. The best way to do this is to add another substance that’s more water-soluble than oil.
How Mixing Works: Emulsification
An emulsion is a liquid that’s made of two or more liquids. When you mix oil and water, you’ve just created an emulsion: an oil-in-water emulsion. To start, droplets of one liquid are suspended in another, creating a three-phase system: two immiscible liquids and an emulsion.
In an emulsion, the droplets of one liquid (the “dispersing phase”) are suspended in another liquid (the “continuous phase”).
The main difference is that an emulsion can be more complex, with more than one type of liquid dispersed in the continuous liquid. Think, for example, of mayonnaise, in which oil, vinegar, and egg yolk are the “dispersing phases” suspended in the “continuous phase” of oil.
We can use salad dressing as another example. If you just mix together the oil and water, you’ll get a thick, lumpy mixture. That’s because the two liquids won’t mix together.
Instead, they’ll form two separate layers: an oil layer on top and a water layer on the bottom. To get them to mix together, you’ll need to do three things:
Break down the oil droplets. Break down the water droplets. Make the fat layer thicker by adding something else (it must have more water in it than the oil does). That’s where emulsification comes in.
This process uses “emulsifiers” that are common in nature and in our technology. An emulsifier is a substance that has a special “taste” for oils and water.
The Science Behind Emulsification
Emulsification is a process whereby two liquids that would not ordinarily mix are combined by breaking one of the liquids down into tiny droplets and suspending them within the other liquid.
The liquids involved in an emulsion can be both organic, like oil and water, or one can be inorganic and the other organic, like water and asphalt.
There are many methods for breaking down liquids into tiny droplets, including using mechanical force, adding an emulsifying agent, or using a chemical reaction. One common method of breaking down liquids is by using mechanical force, such as shaking or stirring.
Another common method is to add an emulsifying agent, which helps to suspend the liquid in smaller droplets. Finally, some chemicals can be used to break down liquids into small droplets through a chemical reaction.
Some emulsifiers are proteins that are found in almost all living things. Others are found in common household cleaners and beauty products. For example, mayonnaise is an emulsifier of oil and vinegar.
This delicious recipe uses an emulsifier found in egg yolks. When you mix oil and water together (without adding any other additives), it’s kind of like trying to get two cars to merge on the highway.
The cars want to stay separate and keep driving on their respective sides of the road. But the cars also want to meet in the middle, so they can drive off together.
You can see this struggle at work when you pour oil and water together. The two liquids try to stay separate, but they also move toward each other to meet in the middle.
So, Are You Stuck With an Impenetrable Layer of Oil & Water?
No, you can actually break down the barrier between the water and oil at the top of the mixture. One way is to simply stir the mixture vigorously. Another way is to add a bit of acid, like vinegar or lemon juice, to the mix. When you add the acid to the mix, it breaks down the oil’s fatty droplets.
The droplets get smaller and smaller until they get so small they can pass through the water barrier. The water ends up with the droplets and the oil ends up on top.
You might be tempted to give up and live with a layer of oil and water on your salad. But there’s a way to get the best of both worlds. First, remember that emulsification is a process of breaking down one liquid into tiny droplets and dispersing it into another liquid.
So, if you want to combine oil and water, you need to break down the oil into tiny droplets and disperse them into the water. Now, the problem is that water and oil don’t mix. So, you need to find a way to get the tiny droplets of oil dispersed into the water.
Finding The Right Balance: Incorporating Other Ingredients with a Mixing Struggle
In order to mix oil and water, you have to create an emulsion: break down the oil and disperse it in the water. This can be done by using a mixer, blender, or even shaking the container.
Next, you need to make sure that the oil droplets are “attractive” enough to the water molecules so that they can actually stay suspended.
If the oil droplets are not attracted to the water molecules, they will quickly separate and rise to the top. While water molecules are generally heavier than oil molecules and thus sink to the bottom of an oil-water mixture, the water molecules in an oil emulsion are “light” enough to stay at the top of the water.
This is due to the fact that oil emulsions are typically created by adding a surfactant to the mixture, which breaks up the water molecules into smaller droplets that are then evenly dispersed throughout the oil.
Bottom Line
To successfully mix oil and water, you need to break down the oil into tiny droplets and then disperse them in the water. Next, you need to make sure that the oil droplets are “attractive” enough to the water molecules so that they can actually stay suspended.
Suppose you want to mix two liquids that normally don’t mix, like oil and water, start by breaking down the oil into tiny droplets and then dispersing them in the water.
Finally, make sure that the oil droplets are attractive enough to the water molecules so that they can actually stay suspended.
During the process of mixing, substances can be transformed in many different ways. For example, when oil and water are combined, they can either form an emulsion or a suspension. To successfully mix substances together, it is important to understand their properties.
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