I’m sure you’ve seen some videos where someone added water to hot cooking oil.
And it’s not pretty.
Can you add water to hot cooking oil?
Definitely not. Not ever. The water will sink to the bottom, rapidly heat up and form steam. And this can lead to all sorts of trouble. Let me explain in more detail what happens.
Can oil and water mix?
No, oil and water can’t mix due to their chemical properties.
Let’s put our science caps on for a moment.
Firstly, to understand why you can’t add water to hot cooking oil, you have to understand why water and oil don’t mix. Even when cold.
You can try and shake it and stir it and curse it, but oil and water won’t mix.
That is because they have different chemical properties.
Water on the one hand is polar. That means that the water molecule has a positive end and it has a negative end.
The positive ends and negative ends of different water molecules are attracted to each other and in this way form strong hydrogen bonds.
These polar ends also help things like sugar and salt to dissolve in water.
An oil molecule, on the other hand, is non-polar. It means it has no poles, so no positive end and no negative end.
Therefore, no bond between the molecules can form.
In fact, oil is what’s called hydrophobic.
That means it falls in a class of substances that repels water molecules instead of attracting them.
Water and oil don’t mix due to their different chemical properties
What happens when you mix oil and water?
From the previous section we know oil and water don’t mix.
So what happens then when you add oil and water together?
Density in liquids is a chemical term that defines how much of a compound there is in a certain space. More specifically, how much weight (mass) per unit volume.
In fluids, the more dense liquid will sink to the bottom while the less dense liquid will float on top.
Water is more dense than oil.
What will happen when you mix oil and water?
When oil and water is mixed, oil will float to the surface and water will sink to the bottom.
And you will end up with a definite top layer of oil and a bottom layer of water.
What happens when you add water to hot oil?
As we’ve seen in the previous section, water will sink to the bottom when added to oil.
And exactly this happens when you add water to hot oil as well.
But here comes the problem.
Oil has a much higher boiling point than water.
So oil can be sitting there doing nothing at 100°C/212°F, while water at that same temperature will boil.
And when water boils, it forms steam.
Furthermore, steam is much less dense than water, which means when it forms, it takes up more space that the same mass of water in liquid form.
So when you add water to hot oil, it starts to sink to the bottom.
Because hot oil can be at temperatures far above the boiling point of water, the oil can start to rapidly boil the water as it sinks.
When the water starts to boil, it forms steam, which takes up more space than the liquid water.
In other words, the water’s volume expands when it goes from liquid to gas form.
You now have a situation where you have a rapidly expanding substance inside the hot oil.
And finally, this rapid expansion of water causes the oil to get blown out of the pot or pan and all over the place.
In summary, when you add water to hot oil, the water will start to sink while rapidly heating up and forming steam, which in turn will expand and cause the hot oil to splatter all over the place.
The situation is totally different, though, when you add cold oil instead o cold water to hot oil.
Why should you not try to extinguish burning oil with water?
Because the burning oil will just get splattered all over the place. And while initially only the oil surface in the pot or other container was on fire, these smaller quantities of oil being sprayed around will also catch fire, making the situation worse.
We’ve seen what happens when you add water to hot oil.
Now imagine the same scenario, but the oil is burning.
Oil can only burn on the surface, because for something to burn, it needs oxygen.
When you add water to hot oil and the reaction causes the oil to splatter all over the place, it increases the surface area of the oil.
That is because of only one flat surface for all your oil, you now have plenty of droplets of oil with surface areas all around the droplet.
And this means there is more surface area to burn.
So the moment the burning oil gets splattered all over the place, the new exposed areas of oil all around the droplets will ignite, and you’ll end up with a big “cloud” of burning oil!
Final thoughts
I hope you have a better understanding of the dynamics at play when you mix oil and water.
And especially when it it comes to hot or burning oil.
Just remember to never add water to oil in the kitchen unless you know the oil is cold and you have a specific goal with your efforts.
Stay safe and happy cooking!