This week's science learning video is about the emergent chemical properties of water. I'll be getting into these properties in more detail in a future video, but today I'm going to cover the main chemical factor that enables many of these properties to emerge: The tendency to form hydrogen bonds with other substances. Here's the video, with a more detailed explanation to follow:
If you're not clear about the way hydrogen bonds work, you should watch this video first:
Oxygen is a strongly electronegative atom. This causes a water molecule to be bipolar. The hydrogen side of the molecule has a weak positive charge, and the oxygen side has a negative charge. These particular chemical properties allows water to form hydrogen bonds with other substances.
These hydrogen bonds have many important consequences. They give water the ability to cohere to itself, resulting in phenomena such as surface tension and the capillary action that moves water up the xylem in plants.
This chemical property also enables water to absorb a lot of heat without changing its temperature. Heat must be absorbed in separating millions of hydrogen bonds before it can start heating up the water. For this reason, water has a relatively high specific heat of 1 cal/gram. It takes a calorie of energy to heat 1 gram of water (one milliliter) one degree centigrade.
You can experience the effect of this specific heat when you are on a beach in the summer. The hot sun beats down on both the sand and the water with equal intensity. But when you walk barefoot on the sand, your feet will burn, while the water still feels cool (or even cold!) against your skin.
The chemical properties of water have important implications for chemistry, life sciences, physics and engineering. Water helps t regulate the temperature of ecosystems, organisms, cells, and machines. Splitting water and removing electrons, a key part of the redox reactions, creates protons which play a role in photosynthesis and metabolism.
Stay tuned for a more detailed video on the chemical properties of water.