Question

)Water at about 4°C (39°F) is more dense than water at 0°C (32°F). Why would the living organisms in the lake die if the water at the freezing point was denser than the water at 4°C

Answer 1

Because the freezing water would sink to the bottom and freeze the lake water from the bottom up.

Step-by-step explanation:

Density differences in the ocean are one of the driving forces responsible for the deep ocean currents that circulate around the world. Denser water tends to sink, while less dense water tends to rise. Cold-water currents occur as the dense cold water at the Earth's poles sinks and slowly moves toward the equator. These currents move masses of water down from the surface and through the deep ocean—taking nutrients, oxygen, and heat with them.

Answer 2

If ice was denser than liquid water, the organisms would die because the ice would sink to the bottom on the container, allowing the water at the top to freeze.
Basically, the lake or pond would freeze solid, killing its occupants. When the lake freezes it insulates the rest of the water beneath it, not allowing it to freeze.
Fun fact: water is one of the only substances whose solid state is denser than its liquid state! Pretty cool huh? Funny how huge ecosystems exist only because of the universes strange quirks! I hope this helps!

-AP Chem student