Eli5 – how can water be made of hydrogen and oxygen?

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Liquid water – made from two types of gas. Makes no sense to me, whatsoever. Water seems to be one of the strangest substances and we completely take it for granted that, apparently, it’s made of gas!

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39 Answers

Anonymous 0 Comments

Gas is just a phase of matter. Hydrogen and oxygen are both solid at certain temperatures and pressures, then liquid, then gas. It’s just that the liquid and solid phases aren’t something you normally come in contact with. But if you’ve ever seen an orbital rocket launch, you’ve seen a tank full of liquid oxygen, and possibly liquid hydrogen (Shuttle and SLS for example).

Then when they join to create H2O, the resulting molecule has completely different chemical properties than either, so its temperatures for the three phases change.

Anonymous 0 Comments

Part of the confusion is the fact that the words “hydrogen” and “oxygen” have multiple and distinct meanings which are often used interchangeably.

Water (a water molecule) is composed of the elements hydrogen and oxygen, specifically an oxygen atom connected to two separate and distinct hydrogen atoms, with the oxygen atom sharing electrons with each hydrogen atom.

“Hydrogen gas” and “oxygen gas” are both ***diatomic molecules***, each composed of two atoms of their respective elements.

Put another way:
The element hydrogen is defined as one proton plus one electron. This is one atom of hydrogen.
The gas known as hydrogen is two hydrogen atoms bound together — that is, two individual protons, sharing two electrons between them, forming a diatomic molecule of hydrogen.

The element oxygen is six protons in a mass with six (sometimes more) neutrons, surrounded by six electrons. This is one atom of oxygen.
Oxygen gas is two atoms of oxygen sharing electrons with one another, forming one diatomic molecule of oxygen.

Anonymous 0 Comments

Part of the confusion is the fact that the words “hydrogen” and “oxygen” have multiple and distinct meanings which are often used interchangeably.

Water (a water molecule) is composed of the elements hydrogen and oxygen, specifically an oxygen atom connected to two separate and distinct hydrogen atoms, with the oxygen atom sharing electrons with each hydrogen atom.

“Hydrogen gas” and “oxygen gas” are both ***diatomic molecules***, each composed of two atoms of their respective elements.

Put another way:
The element hydrogen is defined as one proton plus one electron. This is one atom of hydrogen.
The gas known as hydrogen is two hydrogen atoms bound together — that is, two individual protons, sharing two electrons between them, forming a diatomic molecule of hydrogen.

The element oxygen is six protons in a mass with six (sometimes more) neutrons, surrounded by six electrons. This is one atom of oxygen.
Oxygen gas is two atoms of oxygen sharing electrons with one another, forming one diatomic molecule of oxygen.

Anonymous 0 Comments

Part of the confusion is the fact that the words “hydrogen” and “oxygen” have multiple and distinct meanings which are often used interchangeably.

Water (a water molecule) is composed of the elements hydrogen and oxygen, specifically an oxygen atom connected to two separate and distinct hydrogen atoms, with the oxygen atom sharing electrons with each hydrogen atom.

“Hydrogen gas” and “oxygen gas” are both ***diatomic molecules***, each composed of two atoms of their respective elements.

Put another way:
The element hydrogen is defined as one proton plus one electron. This is one atom of hydrogen.
The gas known as hydrogen is two hydrogen atoms bound together — that is, two individual protons, sharing two electrons between them, forming a diatomic molecule of hydrogen.

The element oxygen is six protons in a mass with six (sometimes more) neutrons, surrounded by six electrons. This is one atom of oxygen.
Oxygen gas is two atoms of oxygen sharing electrons with one another, forming one diatomic molecule of oxygen.

Anonymous 0 Comments

It’s not really made of gas. It’s made of atoms. Heck, you’re 9.5% hydrogen by weight. 65% oxygen and 18.5% carbon and a bunch of other stuff.

Note that water is only liquid between 0 and 100 degrees C, or 32 and 212 F. Below that it’s solid, above that is gas. Hydrogen becomes liquid at -253 C, Oxygen is liquid at -183C. That’s because Hydrogen and Oxygen molecules (which are 2 atoms each) don’t tend to stick together unless they get really really cold. Water molecules on the other hand have some local polarity, so they’re more likely to bond at higher temperatures. Pretty much everything has a solid, liquid, and gas temperature.

Anonymous 0 Comments

It’s not really made of gas. It’s made of atoms. Heck, you’re 9.5% hydrogen by weight. 65% oxygen and 18.5% carbon and a bunch of other stuff.

Note that water is only liquid between 0 and 100 degrees C, or 32 and 212 F. Below that it’s solid, above that is gas. Hydrogen becomes liquid at -253 C, Oxygen is liquid at -183C. That’s because Hydrogen and Oxygen molecules (which are 2 atoms each) don’t tend to stick together unless they get really really cold. Water molecules on the other hand have some local polarity, so they’re more likely to bond at higher temperatures. Pretty much everything has a solid, liquid, and gas temperature.

Anonymous 0 Comments

It’s not really made of gas. It’s made of atoms. Heck, you’re 9.5% hydrogen by weight. 65% oxygen and 18.5% carbon and a bunch of other stuff.

Note that water is only liquid between 0 and 100 degrees C, or 32 and 212 F. Below that it’s solid, above that is gas. Hydrogen becomes liquid at -253 C, Oxygen is liquid at -183C. That’s because Hydrogen and Oxygen molecules (which are 2 atoms each) don’t tend to stick together unless they get really really cold. Water molecules on the other hand have some local polarity, so they’re more likely to bond at higher temperatures. Pretty much everything has a solid, liquid, and gas temperature.

Anonymous 0 Comments

In a gas, molecules fly around freely, with very little interactions between them. In a liquid, molecules are bound together. These bonds break very easily and are in fact broken and reformed all the time. If the bonds were stronger, it would be a solid.

Molecules will tend to stick together for various reasons. For example, hydrogen atoms easily form weak bonds with atoms on the right of the periodic table, like oxygen, fluor… These bonds are called “hydrogen bonds”. (Note that these are bonds between atoms of different molecules. They’re different from the bonds between atoms that form molecules, which are a lot stronger and are called “covalent bonds)

If you have water, hydrogen atoms and oxygen atoms in the water molecules will be attracted to each other. The molecules will stick together and form a liquid. If you have only hydrogen (or only oxygen), they won’t form such bonds and so they will wander freely, forming a gas.

You can give water molecules some energy, by heating them, so that they break these bonds and wander freely too (at 100°C). You can also remove energy from dioxygen molecules, by cooling them, so that they don’t have enough speed, settle down and form a liquid (at around -183°C). But it takes much more energy to break the bonds between water molecules than to break the bonds between dioxygen molecules, so that’s why you have to heat water a lot more to obtain a gas.

Side note : it’s not only water. The boiling point of a molecule doesn’t depend on the boiling point of its atoms. For example, alcohol (named “ethanol” by chemists) is liquid at ambient temperature, but is composed of carbon, hydrogen and oxygen. Carbon is a solid at ambient temperature (it can be the graphite of your pencils, or diamonds), and hydrogen and oxygen are gases.

Anonymous 0 Comments

In a gas, molecules fly around freely, with very little interactions between them. In a liquid, molecules are bound together. These bonds break very easily and are in fact broken and reformed all the time. If the bonds were stronger, it would be a solid.

Molecules will tend to stick together for various reasons. For example, hydrogen atoms easily form weak bonds with atoms on the right of the periodic table, like oxygen, fluor… These bonds are called “hydrogen bonds”. (Note that these are bonds between atoms of different molecules. They’re different from the bonds between atoms that form molecules, which are a lot stronger and are called “covalent bonds)

If you have water, hydrogen atoms and oxygen atoms in the water molecules will be attracted to each other. The molecules will stick together and form a liquid. If you have only hydrogen (or only oxygen), they won’t form such bonds and so they will wander freely, forming a gas.

You can give water molecules some energy, by heating them, so that they break these bonds and wander freely too (at 100°C). You can also remove energy from dioxygen molecules, by cooling them, so that they don’t have enough speed, settle down and form a liquid (at around -183°C). But it takes much more energy to break the bonds between water molecules than to break the bonds between dioxygen molecules, so that’s why you have to heat water a lot more to obtain a gas.

Side note : it’s not only water. The boiling point of a molecule doesn’t depend on the boiling point of its atoms. For example, alcohol (named “ethanol” by chemists) is liquid at ambient temperature, but is composed of carbon, hydrogen and oxygen. Carbon is a solid at ambient temperature (it can be the graphite of your pencils, or diamonds), and hydrogen and oxygen are gases.

Anonymous 0 Comments

In a gas, molecules fly around freely, with very little interactions between them. In a liquid, molecules are bound together. These bonds break very easily and are in fact broken and reformed all the time. If the bonds were stronger, it would be a solid.

Molecules will tend to stick together for various reasons. For example, hydrogen atoms easily form weak bonds with atoms on the right of the periodic table, like oxygen, fluor… These bonds are called “hydrogen bonds”. (Note that these are bonds between atoms of different molecules. They’re different from the bonds between atoms that form molecules, which are a lot stronger and are called “covalent bonds)

If you have water, hydrogen atoms and oxygen atoms in the water molecules will be attracted to each other. The molecules will stick together and form a liquid. If you have only hydrogen (or only oxygen), they won’t form such bonds and so they will wander freely, forming a gas.

You can give water molecules some energy, by heating them, so that they break these bonds and wander freely too (at 100°C). You can also remove energy from dioxygen molecules, by cooling them, so that they don’t have enough speed, settle down and form a liquid (at around -183°C). But it takes much more energy to break the bonds between water molecules than to break the bonds between dioxygen molecules, so that’s why you have to heat water a lot more to obtain a gas.

Side note : it’s not only water. The boiling point of a molecule doesn’t depend on the boiling point of its atoms. For example, alcohol (named “ethanol” by chemists) is liquid at ambient temperature, but is composed of carbon, hydrogen and oxygen. Carbon is a solid at ambient temperature (it can be the graphite of your pencils, or diamonds), and hydrogen and oxygen are gases.