[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:08.47,0:00:11.71,Default,,0000,0000,0000,,There are over one billion cars\Nin the world today,
Dialogue: 0,0:00:11.71,0:00:13.37,Default,,0000,0000,0000,,getting people where they need to go,
Dialogue: 0,0:00:13.37,0:00:16.26,Default,,0000,0000,0000,,but cars aren't just\Na mode of transportation,
Dialogue: 0,0:00:16.26,0:00:18.78,Default,,0000,0000,0000,,they're also a chemistry lesson\Nwaiting to be taught.
Dialogue: 0,0:00:18.78,0:00:22.28,Default,,0000,0000,0000,,The process of starting your car\Nbegins in the engine cylinders,
Dialogue: 0,0:00:22.28,0:00:24.79,Default,,0000,0000,0000,,where a spritz of gasoline\Nfrom the fuel injector
Dialogue: 0,0:00:24.79,0:00:26.81,Default,,0000,0000,0000,,and a gulp of air\Nfrom the intake valve
Dialogue: 0,0:00:26.81,0:00:29.84,Default,,0000,0000,0000,,mix together before \Nbeing ignited by a spark,
Dialogue: 0,0:00:29.84,0:00:33.31,Default,,0000,0000,0000,,forming gases that expand and push the piston.
Dialogue: 0,0:00:33.31,0:00:37.14,Default,,0000,0000,0000,,But combustion is an exothermic reaction,\Nmeaning it releases heat.
Dialogue: 0,0:00:37.14,0:00:38.63,Default,,0000,0000,0000,,Lots of it.
Dialogue: 0,0:00:38.63,0:00:41.16,Default,,0000,0000,0000,,And while much of this heat escapes\Nthrough the tail pipe,
Dialogue: 0,0:00:41.16,0:00:46.32,Default,,0000,0000,0000,,the heat that remains in the engine block\Nneeds to be absorbed, transported, and dissipated
Dialogue: 0,0:00:46.32,0:00:49.74,Default,,0000,0000,0000,,to protect the metal components\Nfrom deforming or even melting.
Dialogue: 0,0:00:49.74,0:00:51.63,Default,,0000,0000,0000,,This is where the cooling system comes in.
Dialogue: 0,0:00:51.63,0:00:54.45,Default,,0000,0000,0000,,A liquid gets circulated\Nthroughout the engine,
Dialogue: 0,0:00:54.45,0:00:56.83,Default,,0000,0000,0000,,but what kind of liquid\Ncan absorb all that heat?
Dialogue: 0,0:00:56.83,0:00:59.21,Default,,0000,0000,0000,,Water may seem like an obvious first choice.
Dialogue: 0,0:00:59.21,0:01:00.84,Default,,0000,0000,0000,,After all, its specific heat,
Dialogue: 0,0:01:00.84,0:01:03.52,Default,,0000,0000,0000,,the amount of energy required\Nto raise the temperature
Dialogue: 0,0:01:03.52,0:01:05.96,Default,,0000,0000,0000,,of a given amount\Nby one degree Celsius,
Dialogue: 0,0:01:05.96,0:01:08.39,Default,,0000,0000,0000,,is higher than that of\Nany other common substance.
Dialogue: 0,0:01:08.39,0:01:10.89,Default,,0000,0000,0000,,And we have a lot of heat energy to absorb.
Dialogue: 0,0:01:10.89,0:01:13.13,Default,,0000,0000,0000,,But using water can get us\Ninto deep trouble.
Dialogue: 0,0:01:13.13,0:01:16.76,Default,,0000,0000,0000,,For one thing, its freezing point\Nis zero degrees Celsius.
Dialogue: 0,0:01:16.76,0:01:19.02,Default,,0000,0000,0000,,Since water expands\Nas it freezes,
Dialogue: 0,0:01:19.02,0:01:23.10,Default,,0000,0000,0000,,a cold winter night could mean\Na cracked radiator and a damaged engine block,
Dialogue: 0,0:01:23.10,0:01:24.53,Default,,0000,0000,0000,,a chilling prospect.
Dialogue: 0,0:01:24.53,0:01:26.76,Default,,0000,0000,0000,,And considering how hot\Ncar engines can get,
Dialogue: 0,0:01:26.76,0:01:30.14,Default,,0000,0000,0000,,the relatively low boiling point\Nof 100 degrees Celsius
Dialogue: 0,0:01:30.14,0:01:32.97,Default,,0000,0000,0000,,can lead to a situation\Nthat would get anyone steamed.
Dialogue: 0,0:01:32.97,0:01:35.51,Default,,0000,0000,0000,,So, instead of water,\Nwe use a solution,
Dialogue: 0,0:01:35.51,0:01:39.51,Default,,0000,0000,0000,,a homogeneous mixture consisting\Nof a solute and a solvent.
Dialogue: 0,0:01:39.51,0:01:44.26,Default,,0000,0000,0000,,Some of the solution's properties will differ\Ndepending on the proportion of solute present.
Dialogue: 0,0:01:44.26,0:01:48.08,Default,,0000,0000,0000,,These are called colligative properties,\Nand as luck would have it,
Dialogue: 0,0:01:48.08,0:01:51.40,Default,,0000,0000,0000,,they include freezing point depression\Nand boiling point elevation.
Dialogue: 0,0:01:51.40,0:01:56.98,Default,,0000,0000,0000,,So, solutions have both a lower freezing point\Nand a higher boiling point than pure solvent,
Dialogue: 0,0:01:56.98,0:02:00.00,Default,,0000,0000,0000,,and the more solute is present,\Nthe bigger the difference.
Dialogue: 0,0:02:00.00,0:02:02.37,Default,,0000,0000,0000,,So, why do these properties change?
Dialogue: 0,0:02:02.37,0:02:05.35,Default,,0000,0000,0000,,First of all, we need to understand that\Ntemperature is a measure
Dialogue: 0,0:02:05.35,0:02:07.73,Default,,0000,0000,0000,,of the particle's average kinetic energy.
Dialogue: 0,0:02:07.73,0:02:10.30,Default,,0000,0000,0000,,The colder the liquid,\Nthe less of this energy there is,
Dialogue: 0,0:02:10.30,0:02:12.31,Default,,0000,0000,0000,,and the slower the molecules move.
Dialogue: 0,0:02:12.31,0:02:14.84,Default,,0000,0000,0000,,When a liquid freezes,\Nthe molecules slow down,
Dialogue: 0,0:02:14.84,0:02:17.22,Default,,0000,0000,0000,,enough for their attractive forces\Nto act on each other,
Dialogue: 0,0:02:17.22,0:02:20.28,Default,,0000,0000,0000,,arranging themselves into a crystal structure.
Dialogue: 0,0:02:20.28,0:02:23.54,Default,,0000,0000,0000,,But the presence of solute particles\Ngets in the way of these attractions,
Dialogue: 0,0:02:23.54,0:02:27.95,Default,,0000,0000,0000,,requiring a solution to be cooled down further\Nbefore the arrangement can occur.
Dialogue: 0,0:02:27.95,0:02:30.77,Default,,0000,0000,0000,,As for the boiling point,\Nwhen a liquid boils,
Dialogue: 0,0:02:30.77,0:02:32.90,Default,,0000,0000,0000,,it produces bubbles filled with its vapor,
Dialogue: 0,0:02:32.90,0:02:36.93,Default,,0000,0000,0000,,but for a bubble to form,\Nthe vapor pressure must become as strong
Dialogue: 0,0:02:36.93,0:02:40.31,Default,,0000,0000,0000,,as the atmosphere constantly pushing down\Non the surface of the liquid.
Dialogue: 0,0:02:40.31,0:02:43.07,Default,,0000,0000,0000,,As the liquid is heated, \Nthe vapor pressure increases,
Dialogue: 0,0:02:43.07,0:02:45.69,Default,,0000,0000,0000,,and when it becomes equal\Nto the atmospheric pressure,
Dialogue: 0,0:02:45.69,0:02:48.28,Default,,0000,0000,0000,,the bubbles form and boiling occurs.
Dialogue: 0,0:02:48.28,0:02:51.40,Default,,0000,0000,0000,,A solution's vapor pressure is lower\Nthan that of pure solvent,
Dialogue: 0,0:02:51.40,0:02:54.33,Default,,0000,0000,0000,,so it must be heated\Nto an even higher temperature
Dialogue: 0,0:02:54.33,0:02:56.79,Default,,0000,0000,0000,,before it can match \Nthe strength of the atmosphere.
Dialogue: 0,0:02:56.79,0:02:59.36,Default,,0000,0000,0000,,As an added bonus,\Nthe pressure in the radiator
Dialogue: 0,0:02:59.36,0:03:01.21,Default,,0000,0000,0000,,is kept above atmospheric pressure,
Dialogue: 0,0:03:01.21,0:03:04.90,Default,,0000,0000,0000,,raising the boiling point\Nby another 25 degrees Celsius.
Dialogue: 0,0:03:04.90,0:03:07.91,Default,,0000,0000,0000,,The solution commonly used \Nfor a car's cooling system
Dialogue: 0,0:03:07.91,0:03:11.39,Default,,0000,0000,0000,,is a 50/50 mixture of \Nethylene glycol and water,
Dialogue: 0,0:03:11.39,0:03:17.53,Default,,0000,0000,0000,,which freezes at -37 degrees Celsius\Nand boils at 106 degrees Celsius.
Dialogue: 0,0:03:17.53,0:03:21.22,Default,,0000,0000,0000,,At the highest recommended proportion\Nof 70 to 30,
Dialogue: 0,0:03:21.22,0:03:25.16,Default,,0000,0000,0000,,the freezing point is even lower\Nat -55 degrees Celsius,
Dialogue: 0,0:03:25.16,0:03:29.03,Default,,0000,0000,0000,,and the boiling point rises\Nto 113 degrees Celsius.
Dialogue: 0,0:03:29.03,0:03:31.62,Default,,0000,0000,0000,,As you can see,\Nthe more ethylene glycol you add,
Dialogue: 0,0:03:31.62,0:03:34.70,Default,,0000,0000,0000,,the more protection you get,\Nso why not go even higher?
Dialogue: 0,0:03:34.70,0:03:37.48,Default,,0000,0000,0000,,Well, it turns out you can have\Ntoo much of a good thing
Dialogue: 0,0:03:37.48,0:03:38.75,Default,,0000,0000,0000,,because at higher proportions,
Dialogue: 0,0:03:38.75,0:03:41.83,Default,,0000,0000,0000,,the freezing point actually\Nstarts to go back up.
Dialogue: 0,0:03:41.83,0:03:45.27,Default,,0000,0000,0000,,The properties of the solution head towards\Nthe properties of ethylene glycol,
Dialogue: 0,0:03:45.27,0:03:48.26,Default,,0000,0000,0000,,which freezes at -12.9 degrees Celsius,
Dialogue: 0,0:03:48.26,0:03:51.29,Default,,0000,0000,0000,,a higher temperature than we \Nattained with the solution.
Dialogue: 0,0:03:51.29,0:03:54.98,Default,,0000,0000,0000,,The solution flows through the engine,\Nabsorbing heat along the way.
Dialogue: 0,0:03:54.98,0:03:57.73,Default,,0000,0000,0000,,When it reaches the radiator,\Nit's cooled by a fan,
Dialogue: 0,0:03:57.73,0:04:00.28,Default,,0000,0000,0000,,as well as air rushing through\Nthe front of the car
Dialogue: 0,0:04:00.28,0:04:02.87,Default,,0000,0000,0000,,before returning to the hot engine compartment.
Dialogue: 0,0:04:02.87,0:04:04.84,Default,,0000,0000,0000,,So, an effective and safe engine coolant
Dialogue: 0,0:04:04.84,0:04:09.42,Default,,0000,0000,0000,,must have a high specific heat, \Na low freezing point, and a high boiling point.
Dialogue: 0,0:04:09.42,0:04:13.41,Default,,0000,0000,0000,,But instead of searching all over the world\Nfor the perfect liquid to solve our problem,
Dialogue: 0,0:04:13.41,0:04:15.84,Default,,0000,0000,0000,,we can create our own solution.