Water – Liquid Awesome: Crash Course Biology #2

Hank teaches us why water is one of the most fascinating and important substances in the universe.

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Re-watch = 00:00
Introduction = 00:42
Molecular structure & hydrogen bonds = 01:38
Cohesion & surface tension = 02:46
Adhesion = 03:31
Hydrophilic substances = 04:42
Hydrophobic substances = 05:14
Henry Cavendish = 05:49
Ice Density = 07:45
Heat Capacity = 09:10

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TAGS: water, hydrogen, oxygen, molecule, covalent bond, cohesion, adhesion, polarity, hydrogen bond, surface tension, capillary action, hydrophilic, hydrophobic, ionic bond, ion, universal solvent, henry cavendish, chemistry, specific gravity, density, heat capacity, evaporation, biology, crashcourse, crash course, hank green Support CrashCourse on Patreon: https://www.patreon.com/crashcourse


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  1. Notes:
    Connection between water and life

    Water molecules have high cohesion (attraction between the polar particles), leading to high surface tension. You can see this when drops on a leaf sticking to each other.

    Adhesion, opposite of cohesion, leads to spreading out instead of beading up

    Capillary action: ability to defy gravity by adhesive forces of a platform (like a straw) and cohesive forces of other water molecules to them. This is balanced by pressure and gravity.

    Water is a great solvent (many things can dissolve in it)

    Hydrophilic like salt: polars that dissolve in water, have stronger polarity than water's cohesion

    Hydrophobic like oil

    Ice has lower density than liquid water and floats (counter to how other elements behave). Because at 0 deg C, crystal structures with even spacing between them take more space. This allows life above and beneath the ice (as oppose to frozen depths and rising waters)

    Water has high heat capacity (how much heat for how long could be soaked and stored by a material), good at holding heat. That makes heating up and cooling down oceans difficult, so they can regulate the temperature. This is how sweating cools your body.

  2. The voice inflection you put on during some of these videos is quite annoying and distracting… I would enjoy these more if you just spoke naturally.

  3. "So around 32 degrees Fahrenheit… or 0 degree Celsius if you're a scientist or from a part of the world where things make sense" YES, YES THAT IS WHAT I LIKE TO SEE! ( I mean, American don't have much sense dont they? ) (OK, please accept this as a fact, I can't stop viewing republicans as idiots due to the fact that they elected a president who made a nuclear threat to the world a common thing every single day. Basically me every morning: "Did he launch missile yet? No? He didn't? Awwwww…..)

  4. When the vast majority of people are here because of a test, and you're literally just watching this because they replaced all of your documentaries with reality shows on the discovery channel.

  5. Let's discuss the mechanic's of Water. Could you explain, how 70% of the Earth's surface 'Water', bends around a Space rock!? Water at rest will always remain level, maybe thats why they call it Water level…

  6. A summary!

    Video Two: Water

     H2O uses a covalent bond: each hydrogen shares an electron with oxygen. It is thus a polar molecule.

     All water molecules are attracted to each other due to this polarity – these are hydrogen bonds (between the positive and negative poles of different molecules)

     Hydrogen bonds in water results in high cohesion, and thus high surface tension.

     Cohesion is the attraction between two like things (e.g. two water molecules).

     Water has the highest cohesion of any non-metallic liquid.

     Adhesion is the attraction between two unlike things (e.g. water and glass).

     Capillary action is water defying gravity.

     Water is the greatest solvents (due to its polarity).

     Hydrophilic molecules are polar – their polarity is stronger than the cohesive forces of water.

     Hydrophobic molecules cannot break the cohesive forces of water because they are non-polar.

     Solid water is less dense than liquid water due to hydrogen bonds forming crystalline structures that space molecules apart more easily (when frozen).

     Water has a very high heat capacity – it is good at holding on to heat, thus oceans regulate climate and temperature of planets.

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