Water Lab Conclusion

From Rubric:

Write a few paragraphs about water, water molecules, water properties, solubility of solutes in water, heat capacity constant, etc.  Show off how much chemistry you know about water.

Copy, do not type or copy and paste:

Water is a molecule of three atoms with a formula of H2O.  The oxygen is central and makes two single polar covalent bonds with the two hydrogen atoms.  Oxygen has a 3.4 electronegativity value, while hydrogen has only a 2.2 value.  Since there is a (big) difference, the bonds are single POLAR covalent. 

It is a bent molecule, and therefore has no radial symmetry.  It’s a polar molecule.  Since it’s a polar molecule with polar bonds, containing hydrogen atoms, the molecule has a lot of hydrogen bonding between the molecules, which gives the (small sized) compound high boiling points, low vapor pressure and high melting points. 

Since water is a polar molecule, it will only dissolve polar molecules (like table sugar or alcohol) or ionic salt compounds (not all, check table F).  Nonpolar molecules, such as octane, methane, or carbon tetrabromide do not dissolve.  Small amounts of carbon dioxide or oxygen (CO2 or O2) can be forced into water with higher than normal pressures, but open to the air, these gases tend to bubble out of solution (soda and seltzer get flat quickly).

Water has a high specific heat capacity constant.  That means it is hard to change the temperature of water, compared to other substances.  The “C” value for water is 4.18 J/g·K.

On table G we see that many substances dissolve into water.  Most of the ionic compounds will dissolve less well in cooler water, but to a much greater degree in hotter water.  The hotter water has much greater kinetic energy, and the water molecules can (literally) “juggle” more ions in solution.

For molecular compounds, the opposite is true:  Hotter aqueous solutions hold LESS molecular compounds, which tend to bubble into gases and fizz out of solution.  Colder aqueous solutions can hold more molecular compounds (like CO2) because of lower kinetic energy which does not shake the compounds out of solution as readily.  Open to the air, all carbonated solutions will go flat.

Ice, which is solid H2O, can float in liquid water.  This is actually a fairly unusual characteristic, and allows for life to exist on Earth.  If ice sank due to a higher density, in less than 100 years all of the water on Earth would be fully frozen, and only a small top layer would melt each summer.  Because of that, there would be no water to nourish animals or allow for plants to grow, and it short order, all life would end.  If this were the case, no life would have evolved (most likely) due to this serious lack of free water in the environment.

Water can also hydrogen bond to ionic compounds, like with CuSO2·5H2O.

Water cannot conduct electricity, it has no loose or mobile ions.  But since water readily dissolves most ionic compounds, water can often conduct when salted.  The ions make it an electrolyte.

Most properties of water are due to hydrogen bonding between molecules.  Water is also fun to swim in, which I will do later.  I love chem, the end.


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