A piece of wood floats in water, completely inside it. What happens when it is dropped in ethanol?
A. It floats higher
B. Stays as before
C. It sinks
D. It sinks first and then rises

Hint: The different densities of the two liquids gives us the solution to this problem. If the buoyant force equals the object’s weight, the object will remain suspended at that depth.

Complete step by step solution:
The density of ethanol is 0.79 g/cc and the density of water is 1 g/cc.
We can say from the above statement that the density of ethanol is less than the density of water.
We will see this problem which will work on the fact that pressure increases with depth in a fluid. This means that the upward force on the bottom of an object in a fluid is greater than the downward force on the top of the object. There is a net upward, or buoyant force on any object in any fluid. If the buoyant force is greater than the object’s weight, the object will rise to the surface and float. If the buoyant force is less than the object’s weight, the object will sink.
So, the piece of wood which floats in water when placed in ethanol it sinks.

Thus, option C is correct.

Additional information: The phenomenon mentioned above purely depends upon the law of flotation.

Note: Law of flotation is an application of Archimedes principle.
The buoyant force is always present whether the object floats, sinks, or is suspended in a fluid.