Coin in the well

Place a coin in a dish of water. How can you get it out, without putting your hand in the water or pouring the water from the dish?

Put a burning piece of paper in a tumbler and invert it on the dish next to the coin. The water rises into the tumbler and releases the coin.

During combustion the carbon contained in the paper, together with other substances, combines with the oxygen in the air to form carbon dioxide. The gas pressure in the tumbler is reduced by the expansion of the gases on heating and contraction on cooling. The air flowing in from outside pushes the water into the tumbler.