Why are oil and water immiscible?

Question

like in the lava lamp

Answer 1

The fundamental answer is that the intermolecular forces between the polar water molecules is stronger than the forces between the water molecules and the non-polar molecules in the oil.  That means that water squeezes out the non-polar molecules.  

In a lava lamp, the cooler oil has a higher density than the water, so it sinks to the bottom.  When it heats up, it has a lower density than the water, so it rises to the top.  At the top, the oil again cools and sinks to the bottom.  However, in this process, the oil and water do not mix because of the polarity characteristics.

The clever design of the lava lamp was the choice of the oil that would have just the right density when cold to sink and just the right density when warm to rise.

Answer 2

Because they have different density's.

Answer 3

They are not "like dissolve like." Water is a good solvent for polar molecules because it is a POLAR SOLVENT, but it is not for non-polar or semi-polar.

Density of the oil is much heavier than density of water that is the reason oil and water will never mix.

I hope that helps :)