Why did this happen ?

A body which floated in water sank, when put in kerosene. Why did it happen?

You might have felt that your ears have 'popped' when you were in a plane taking off or in a car travelling down a steep mountain road. Why did it happen?

Take a glass of water and put some ice cubes inte it. Observe it for some time. What happens? The ice cubes melt and disappear. Why did it happen?

What is gout and why does it happen?