| Today for a little background of our all class lab, we learned about ionic compounds and covalent compounds. Covalent compounds are created when more than one nonmetal atoms bond together and share valence electrons. When nonmetal atoms share valence electrons, they are gaining and losing electrons to make the outer-shell as full as it can possibly be. When they share the valence electrons, this is called a covalent bond A nonpolar covalent bond means that two atoms share a pair of electrons. The bond between two chlorine atoms is an example of a nonpolar covalent bond because they equally share atoms. A polar covalent bond is when two atoms don't share the electrons equally. One atom has more of a stronger pull than the other, and will attract more electrons than the other. H2O (water) is an example of a polar covalent bond. The electrons are shared unequally. The oxygen atom attracts more electrons than hydrogen atoms. Nonmetals gain electrons to form negative ions. In this experiment, we are trying to make sand that "can't get wet". Polarity is the difference in charge across an atom. An example of something polar is water. Water can help dissolve most things, like salt. When water dissolves salt, it separates the the sodium and the chloride, so that little particles of each are separated in the water. That means it's dissolved. Acetone is non-polar, and can take off nail polish, meaning that nail polish is also non-polar. Our experiment of polarity, was on sand. We sprayed a thin layer of pink reptile/lizard sand with silicon spray, (the same kind used for furniture so nothing stains onto it) and let it dry. Four sprays later, we brought our sand back into the classroom. We poured a little bit of sand into the water, and watched it. It seemed to stick together, and not separate one bit. The hydrophobic spray helped the sand become hydrophobic as well. Hydrophobic means that it doesn't absorb water. The experiment turned out to work really well. According to Andrew, it didn't work very well in the morning class. It was really interesting to take the sand that's in the water, and pull it out of the water. It would separate and turn back into dry sand. With my group, we seemed to be really happy with the results. I don't think we were expecting it to work either. If I were to change what we did, I would add more sand, or see how little we would need, or the ratio to make it work no matter what. I would probably choose to work by myself next time. I now know the meaning of hydrophobic and hydrophilic. As well as polar and nonpolar. I'd like to try different experiments with the same concepts, like oil and water. |