Hydrogen (H) and oxygen (O) are two gases under STP. So why is Water liquid in the same conditions?

Question

(H) and oxygen (O) are two gases under standard conditions for temperature and pressure, STP. So why is Water, H2O, liquid in the same conditions?

Answer 1

Because in the H2 and O2 molecules, the atoms are the same, and so there is no separation of charges within the molecules. In the H2O molecule, which is H-O-H, the electrons are unequally shared, leading to a slight + charge on each H and a slight - charge on each O. The H's of one molecule are attracted to the O's on other molecules. This attraction of molecules for one another is so strong, that O2, molecular weight 32, boils hundreds of degrees below zero, whereas H2O, molecular weight 18, boils at +100degC.

Answer 2

In chemistry you are governed by 2 laws:

Law of minimum Enthalpy (energy)

and Law of Maximum Entropy (randomness)

When hydrogen and oxygen react to form water, energy is released, since the enthalpy has decreased, it is permissible for the Entropy to decrease (liquid is less random than gas). This seems maybe counter intuitive, you might think why not keep the entropy the same, and stay gas; It is easier to start from the reverse position and accept that liquid water at STP is its natural condition - In order to break it down into H & O you must add energy thus enthalpy - To balance this, you must also increase randomness, thus the reaction results are gases.

Answer 3

The boiling points for oxygen and hydrogen are below "standard temperature" which is 0 degrees C. So at STP, they are already gases.

The boiling point of water is above "standard temperature" so it hasn't boiled yet. Its melting point IS 0 degrees celcius and at that temperature under IDEAL conditions absolutely pure water is both melting and freezing so both solid and liquid would be present at the same time. If the temperature were just a "hair" higher than 0 it would all melt.

Answer 4

Water has a lower potential energy than either Hydrogen or Oxygen gases. Therefore, upon creation of water the reaction was violently exothermic (H2+O2) so it lost much of it's energy. Therefore to be in a gas state (a highly excited state) water molecules require much more energy than provided at STP. Also, water has much more powerful intramolecular forces (hydrogen bonding) which keeps the molecules together very well.

Answer 5

If it was merely a matter of molecular weight and thermal inertia, you would think that water would boil at a temp between that of O2 and H2, since its molecular weight is also between that of O2 and H2.

But.

H20 is not a straight molecule, instead of being

H
O
H

it is more

H
..O
H

and thus, has a charge "polarity. The middle "O" part is more negative and the H parts are more positive. As a result, in liquid water, long chains and arrays and networks of water molecules form which _act_ as though their molecular weights are higher than that of the constituent water molecules.

This stickyness of the molecules results in a vastly higher boiling point.

Answer 6

Compounds don't have the comparable characteristics as their components. Take NaCl, sodium chloride(table salt). sodium is a toxic metallic. Chlorine is a toxic gasoline. mutually they seem to be a white good that we adore on our nutrients and our physique particularly desires a small quantity. Water is a wierd compound besides. Its melting and boiling element are very close, lots closer than maximum compounds. It additionally has an rather severe warmth skill that's why it somewhat is used to soak up warmth.(maximum organic fabric)

Answer 7

because at standard temperature and pressure H2O exists as liquid

Answer 8

The properties of a compound are not limited to the properties of the constituent elements.

Many compounds which have the noble gases, for instance, as one of their elements are stable solids.(fluorides of xenon, for instance)

;-)