Which is more polar; water (H20) or methane (CH4)? And why?

Answer 1

Water is slighty polar since the hydrogen have a more postive charge since the oxygen pulls the electron closer since its electron negative then Hydrogen. Anyways Water is more polar and since CH4 has a carbon in the centre and 4 hydrogen around it it is symentrical so hence not polar to view CH4 check out this site
http://en.wikipedia.org/wiki/CH4

Answer 2

It has to do with electronegativity.

Whether a particular bond is more or less polar is going to depend on the electronegativities of the two atoms involved. Electronegativity can be thought of as how hard an atom pulls on electrons. When the electonegativites are equal, the bond is nonpolar. As the difference accumulates, it becomes more and more polar, culminating in a situation where one atom has all the eletrons and the other wanders off because it has none.

Electronegativity tends to follow a trend of increasing as you go up and to the right on the periodic table. So F is the most electronegative atom around (at 3.98), and Fr is pretty much the least (at 0.7). C has an electronegativity of 2.55, O is 3.44, and H has 2.20 (I looked these up - nobody memorizes them).

So an O-H bond has a difference of 1.24. Pretty polar. A C-H bond has a difference of only 0.35. Hardly polar at all.

But all the polarity would be meaningless if it weren't for the molecular geometry. To find the net polarity of the molecule, you need to add all the polarities together (draw them out and connect them, if need be!). H2O is bent with both Hs pointing off to one side. This means the molecule has a net pull toward the O and away from the Hs. If H2O were a straight line instead, the O would pull from both ends toward the middle, and it wouldn't be polar at all.

You can see an example of the latter if you consider CO2. It DOES have a straight line geometry, so even though the C-O bond is much more polar than a C-H one, the polarity cancels out!

A link below explains a lot of this in greater detail. Hope that helps!

Answer 3

The last two anwers are mostly right, but there's a point to be made: the water molecule is BENT. If the shape of the water molecule was the same as the shape of CO2 - ie, a straight line - water would not be polar. But since it's bent, it isn't symmetric in every direction like methane is. The asymmetry results in what is called a net dipole moment, with greater electronegativity on the oxygen pulling electrons from the hydrogen.

Methane is more symmetric: rotationally, planar, etc. And it has more planes and axes of symmetry. That makes it more balanced.

Take a look at the links to see what I mean.

Answer 4

Is Methane Polar

Answer 5

All the above answers are correct, but not very useful in practice because, they do not enable you to assess if a substance is polar or not. So let me try.

Polarity expresses the degree of electronegativity of a molecule. Oxygen,tends to make molecules polar and hydrogen to make them non polar. Asymmetry (non-symmetry) in a molecule also increases polarity.

Water, because of the high proportion of O in relation to H, and also because the molecule is bent, it is very highly polar, while CH4, because it has no O is highly non-polar.

In practice, if a liquid resembles water to some extend, like ethyl alcohol or acetone, sulfuric acid etc, we can expect it to be polar and the more polar it is, the more it
will dissolve the substances that are soluble in water, such as common salt etc..

Answer 6

Water is more polar.

Differences in the electronegativity of oxygen and hydrogen result in highly polarised bonds. (O negative, H positive)

This does not exist in methane which is non-polar

Answer 7

water, because methane isnt polar.