Double layer forces

Imagine you have two magnets. If you try to push them together with opposite ends facing each other, they will stick together. This is because of something called attraction – the two magnets are attracted to each other.

Now, imagine you have two particles floating in water. Like the magnets, these particles can also feel attraction to each other. But unlike the magnets, there's water between the particles that can get in the way.

When two particles are close together in water, a layer of water molecules forms around each particle. This is called the "double layer." The water in the double layer has a different charge than the bulk of the water around the particles. This difference in charge creates a force that can either attract or repel the particles.

If the particles have the same charge, the double layer force will be repulsive. This means the particles will try to move away from each other. If the particles have opposite charges, the double layer force will be attractive. This means the particles will try to come together.

So, just like the magnets, particles in water can stick together or repel each other depending on their charges and whether they're close enough for the double layer force to come into play.