biology homework/like to understand it better.

[Guest Orange]

Hi, My name is Orange and I'm new here. And I just started to learn about science like biology. So Im a newbie in this section!! hehe.. And There are some things that I don't understand on my biology homework and hope any of you nice smart people would help me out.

I have a few questions that I don't understand about atoms and everything...Can someone help me and give me some clue so I can understand it better? Thanks

 

Question 1: I understand that water is consider a polar molecule, but then how does hydrogen bond relate to it?

 

Question 2: How and why water form spheres like droplets when it flung into the air? ( I don't quiet get how the water became droplets and how it works as a molecule)

I've read my book, but it doesn't say anything..

 

and my last question that came to mind was:

How were the seasonal nutrient and oxygen cycling within a lake is facilitated by the unique density properties of water?

 

Please email you anyone wishes too.. My email is Sweet_Orange84@hotmail.com

 

Thanks

Orange

[coquina]

That's the scientific word for biological or geological processes that concern lakes. I don't know about why water forms droplets, but I think it has something to do with the cohesiveness of the molecular structure. Someone else should be able to help you with that.

 

I found one source that may help - http://www.uib.no/norpec/isotopes.htm

 

Calcium carbonate is commonly present as the mineral calcite or aragonite, formed either biogenically, as mollusc shells, ostracode carapaces or by charophytes, or by direct, apparently abiogenic precipitation from the water column (lake marl). The oxygen isotopic composition of these carbonates is determined by the isotopic composition of the lake water and the temperature of the water at the time of precipitation, both of which are a function of local climate. Carbon isotope ratios in carbonate minerals are little affected by temperature, but the isotopic composition of a lake's pool of dissolved inorganic carbon is strongly influenced by both biological (e.g rates of primary production and remineralisation) and inorganic (e.g. exchange between aqueous and atmospheric CO2) processes, all of which are climatically related. Thus the measured oxygen isotopic composition may provide information on features such as temperature variations, relative rates of inflow versus water loss by evaporation, or changes in the relative importance of the different air masses responsible for the regional water supply. A common problem with oxygen isotope studies of ancient carbonates is that we often operate with two unknowns - the temperature and isotopic composition of the water - but independent ways can often be found to minimise the resulting errors. In addition to rates of primary production, the carbon isotopic composition can provide insights into water column stability.

 

I know that one thing that geologists use to determine past climates are oxygen isotope ratios.

 

From this site: http://palaeo.gly.bris.ac.uk/communication/Willson/isotopeevidence.html

 

Oxygen isotopes

In the hydrologic cycle, evaporation preferentially removes water with oxygen-16 (i.e. light oxygen). This oxygen isotope is therefore rich in the gas phase of water in clouds. Precipitation and runoff returns water with high oxygen-16 to the Earth's surface. During glacial epochs, this precipitated oxygen-16 is preferentially stored in polar icecaps and continental ice sheets. This leaves the oceans enriched in oxygen-18. In the opposite case, when the cliamte is very hot, icecaps do not exist, and oceans are no longer enriched in oxygen-18.

The stable isotopes of oxygen are used to reconstruct palaeoclimates. The abundance of oxygen-18 compared to oxygen-16 is displayed in a ratio of the the two isotopes. The relative value of this ratio is compared to a standard so that the climate change with respect to time can be measured.

 

The ratio of isotopes (signatures) can be recorded in the rocks that are forming at that time. For example, forams create their shell of calcium carbonate from the water and food they consume. When they die and their body sinks to the bottom of the ocean, this isotope signature is preserved in these shells. Sediment accumulates and eventually forms a rock which can become uplifted and be available for study.

 

 

I think when you refer to the "unique density properties of water", you must be refering to relationship of water molecules with O^16, as opposed to o^18.

 

I periods of high evaporation, the lake water will contain a higher ratio of O^18, because the lighter O^16 is preferentially evaporated, and in cold climates or winter, it remains locked in ice, away from the lake.

 

The O16 will eventually be returned to the lake by way of runoff, and as it flows down the streams and rivers, it may react with some of the sediment it picks up. The remaining O^18 in the lake is used my the organisms that live in it. For example, foraminiferas use it to make up their shells.

 

I also know that how much sediment that is returned to the lake is a function of volume and velocity. Of course, the volume depends on the amount of rainfall and ice melt, but the velocity depends on the gradient (steepness) of the surrounding area. The more water, and the steeper the incline, the larger particles the water can carry. In mountain streams, fairly large boulders can be carried, then when the velocity slows down in the foothills the larger boulders are dropped out. As the gradient decreases, the sediments are progressively dropped, from larger to smaller. If the area surrounding the lake is pretty flat, all that is left to be carried into it are finely suspended particles like clay. In times of flood, because of increased volume, more sediment is deposited.

 

I also know that lakes are transient geologically speaking, because over time the sediment running into them fills them up. (This is also a problem with man made reservoirs.)

 

I do not know how the differences with which O^16 and O^18 react with other organic and subtances and nutrients, but I hope I've given you a clue as to where to start.

 

Remember, to use the scientific terms when you google - you'll have a better shot at finding reliable scientific sites.

 

Here's a link to a search for "lacustrine nutrients" on google. Hope this helps.

[chemistry]

1. Water is a polar molecule due to its overall geometrical allignment of its dipole moments (referring to the character of electron sharing between to atoms-dipole moments). Hydrogen bonding exist due to significant electronegativity differences between two atoms and thus a strong dipole moment. However, since the oxygen possess lone pairs, it can intermolecular hydrogen in addition to intramolecular.

 

2. browse through the index for cohesivity or surface tension.

 

3. I'm not quite sure about this one, however, it pertains to the different density between ice and liquid h20 perhaps. Ice has a smaller density, which is opposite of the trend between other liquids and solids.

 

2.