WEBVTT - Why can't we breathe underwater?

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<v Speaker 1>Welcome to Brainstuff from how Stuff Works dot com where

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<v Speaker 1>smart Happens. Hi Am Marshall Brain with today's question. If

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<v Speaker 1>water is made up of hydrogen and oxygen, then why

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<v Speaker 1>can't we breathe underwater? One thing about chemicals is that

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<v Speaker 1>once they react in certain ways, they form compounds that

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<v Speaker 1>are often nothing like the original elements. For example, if

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<v Speaker 1>you react carbon, hydrogen and oxygen together one way, you

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<v Speaker 1>get glucose. If you react them together another way, you

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<v Speaker 1>get vinegar. If you react them together in another way,

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<v Speaker 1>you get fat. If you react them in another way,

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<v Speaker 1>you get ethanol. Glucose, Fat, ethanol, and vinegar are nothing

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<v Speaker 1>like each other, but they are all made from the

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<v Speaker 1>same elements. In the case of hydrogen and oxygen gas,

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<v Speaker 1>if you react them together one way, you get liquid water.

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<v Speaker 1>The reason we can't breathe liquid water is because the

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<v Speaker 1>oxygen used to make the water is bound to two

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<v Speaker 1>hydrogen atoms, and we cannot breathe the resulting liquid. The

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<v Speaker 1>oxygen is useless to our lungs. In this form, the

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<v Speaker 1>oxygen that fish breathe is not the oxygen in H

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<v Speaker 1>two O. Instead, the fish are breathing O two oxygen

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<v Speaker 1>gas that's dissolved in that water. Many different gases dissolve

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<v Speaker 1>in liquids, and we can see an example all the

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<v Speaker 1>time in carbonated beverages. In these beverages, there's so much

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<v Speaker 1>carbon dioxide gas dissolved in the water that it rushes

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<v Speaker 1>out in the form of bubbles. Fish breathe that dissolved

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<v Speaker 1>oxygen out of the water using their gills. It turns

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<v Speaker 1>out that extracting the oxygen is not that easy. Air

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<v Speaker 1>has something like twenty times more oxygen in it than

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<v Speaker 1>the same volume of water, plus water is a lot

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<v Speaker 1>heavier and thicker than air, so it takes a lot

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<v Speaker 1>more work to move it around. The main reason why

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<v Speaker 1>gills work for fish is the fact that fish are

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<v Speaker 1>cold blooded, which reduces their oxygen demands tremendously. Warm blooded

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<v Speaker 1>animals like whales breathe air like people do because it

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<v Speaker 1>would be hard to extract enough oxygen using gills. Humans

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<v Speaker 1>can't breathe underwater because our lungs don't have enough surface

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<v Speaker 1>area to absorb enough oxygen from water, and the lining

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<v Speaker 1>of our lungs is adapted to handle air rather than water. However,

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<v Speaker 1>there have been experiments with humans breathing other liquids like

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<v Speaker 1>flora carbons. Flora carbons can dissolve enough oxygen, and our

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<v Speaker 1>lungs can draw that oxygen out. It's just that that

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<v Speaker 1>first breath where you suck in the flora carbons to

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<v Speaker 1>your lungs is not very pleasant. Do you have any

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<v Speaker 1>ideas or suggestions for this podcast? If so, please send

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<v Speaker 1>me an email at podcast at how stuff works dot com.

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