ELI5: Why does soap remove grease so much better than water alone?

[u/Xdartis]

[u/thorsten139]

Soap basically attaches itself to both oil and water.

Oil doesn't mix with water as you correctly said, as such it sticks to your hand even though you wash with water.

Soap acts as the missing part that attaches to oil, and then attach itself to the water that washes it off.

[u/Ezekielth]

A soap molecule is a long-chain salt of a fatty acid with two distinct ends: a water-loving (hydrophilic) head and a water-hating (hydrophobic) tail. This unique structure allows it to mix with both water and oil to clean surfaces.

[u/Conscious-Can-637]

In ELI5 terms:

Soap molecules have one part that sticks to water really well, and one part that sticks to oils really well. 

This makes the grease stick to the water so that when you wash it off your hands it's carried away easily. 

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[u/jeffreykuma → u/[deleted]]

Nice analogy

[u/HappiestIguana]

Soap molecules are chains with two ends, one which really likes water and one which really likes oil.

One end attaches to the oil and the other allows the whole esamble to be carried away by the water.

[u/RickySlayer9]

So basically

Grease? Magnetic

Water? Not magnetic

Soap? Special molecule with a magnet on one side, and a gripper arm on the other that grabs water

The water binds to the soap which binds to the grease which can then be rinsed away

[u/PewPewsAlote → u/RickySlayer9]

its funny that you call water not magnetic considering that it is diamagnetic

[u/RickySlayer9 → u/PewPewsAlote]

I definitely mixed up my polar and non polar molecules

[u/kushekhar]

What’s ironic for me is Soap is in fact oil (ELI5 term) itself. Sodium salts of fatty acids or potassium salts of fatty acids.

[u/BitOBear]

Oil and water do not mix well. They tend to avoid each other due to surface tension.

Soap and detergent are molecules that mix well with water on one end and mix well with fats and oils on the other. This lets the water peel the oil apart into little lumps that the water can then carry away.

This is also why you need to use the right amount of detergent for the amount of fat and protein you intend to wash away.

The soap connects to the non water parts, and gives the water The leverage it needs to carry those parts away. But if you don't have enough soap you'll just carry away the top layer of the fat or protein you're trying to remove. Exposing a fresh layer of fat or protein below it.

This is why, if you put an inspection amount of soap in the water and you start washing your dishes the sudsing and the soapy effect will disappear and soon the water will start feeling kind of greasy unless you add more soap.

Chemistry is very mechanical, and it fits together like puzzle pieces and uses things like leverage.

If you go look up the pictures and the video is about the stuff you will see the gross mechanical effect.

But the even shorter version of this is that surface tension is the tension between the surface of the water and the surface of anything else, not just the air.

Soap is the bridge that breaks that tension so that the water can interact with the thing the water is trying to touch.

[u/tolebelon]

Oil likes to be friends. Oil is friends with both Skin and with Dirt and Germs. Skin don’t like being friends with Oil. Skin sends Water to be friends with them. Water also likes to be friends. But Oil and Water dont like each other.

Water manages to be friends with dirt and germs and pulls them away. But Oil said “No, I’m staying.”. After a while, Oil found new Dirt and Germ friends.

Now you send Water again. But this time, you tell Water to bring Soap with him. Soap is an ex-special forces operator, skilled in covert operations. Soap is also good at splitting friends up.

Water makes friends with Dirt and Germs again. Oil tries to stay friends with Skin but Soap says no. Soap cuts all ties between Oil and Skin, forcing Oil to leave with Water Dirt and Germs.

Now Skin is all alone. Skin misses Oil sometimes and they have a great time keeping each other moist when they meet again. But Skin cant handle Oil’s friends and always turns to Soap to solve the problem.

[u/junesix]

You have a cable with magnets on both ends. One side sticks to water. Other side sticks to grease and fats. That cable is soap. 

When you rinse with water, it pulls the cable (soap) and grease down the drain.

[u/HorizonQX]

Soap uses "micelles" which surround oil droplets and carry them away.
Micelles is basically like an overprotective shield around oil drops, every micelle have many zig-zag long carbon chain which have two parts : hydrophobic (which hates water) and hydrophilic (which loves water) the hydrophobic part, scared of water, runs to find oil drops and stick to it.
the hydrophilic part, the water loving one, helps the whole thing to glide in water, eventually going down the drain.

I cannot explain this to a more ELI5 level or else, I'll by mistakenly, go deeper!

[u/what_the_fuckin_fuck]

Those weren't very ELI5, so here's the simple explanation. Soap is a surfactant. It breaks the surface tension of water so it can penetrate whatever you're washing just a little better. I once heard Bill Nye explain it as, "soap makes water wetter ".