When a recipe calls for melted chocolate, you place some chunks in the saucepan and wait until it melts. While the chocolate melts you slowly add more chunks which sink to the bottom of the melted chocolate. Whilst taking a break you grab a glass of water with a few ice cubes floating at the surface. Why does the solid form of water ,ice, float on the liquid form while the solid form of chocolate drowns in its liquid form?
Why does ice float?
When water temperature reaches zero degrees Celsius, water molecules lose energy and begin to vibrate slower than before. This allows the water to change from the state of liquid to the state of solid.When this occurs, water freezes into the grid like shape shown below.
 |
| The atoms with red dots mark the B layer with O-H-O links ( the oxygen atom of one molecule connected to the hydrogen atom of another molecule connected to another molecule's oxygen atom) pointing up to the next B layer.The non marked atoms are marking the A layer with H-O-H links and leading up to the next A layer. This was described on the third website from the bottom at the end of this page . |
This causes ice to be less dense than its liquid form making it able to float on the surface. Remember that less dense substances are always pushed above the dense substances like warm air being pushed above the cold air.
How does ice's ability to float affect organisms beneath ?
During the harsh winter how do organisms in lakes in colder areas survive? The ice that solidifies above the lake insulates the water beneath ,preserving it and its residents. This allows the water underneath the ice to remain in liquid form.
What if the ice sank to the bottom of the liquid, just as the chocolate sank in the melted chocolate ?Say the ice that formed at the lake and sank to the bottom. This exposes the lake to the freezing winter air. The air molecules bump into the warmer water molecules and ,through conduction, transfer heat. The water molecules are cooler than before. If the water temperature is 0 degrees Celsius, the lake will freeze and eventually ,after repeating this, freeze solid. If the water temperature is not cold enough for the water to become ice, the fish ,or other residents of the lake, may not be able to survive in the new,cool temperature. One break in a food chain will affect the other members of the chain and eventually collapse the chain.
 |
| One break in a food chain will affect and/or collapse the rest. |
