Lab 12

What is an ionic bond? Typically an ionic bond occurs between one metal and one non-metal ion. One atom borrows one or more electrons from another atom. An ionic bond is a type of chemical bond that occurs when one atom loses an electron to form a positive ion and the other atom gains an electron to form a negative ion, which then result in attraction. 2. What is a covalent bond? A covalent bond is a bond that occurs when atoms in a molecule share a pair of electrons. For example, â€Å"the atoms in sugar do not form ions; instead, they are held together because of shared electrons. † 3.Do you think sugar or salt will melt at a higher temperature? Explain your answer. Since sugar is composed of covalent bonds and salt composed of ionic bonds, I think salt will take a higher temperature to melt because salt is bonded together by stronger bonds. Ionic bonds are much stronger than covalent bonds. Covalent bonds are not as strong as ionic bonds so it will not require such a high t emperature to make sugar melt. Part 1 Observations for the sugar solution: There were occasional bubbles off of the steel screw, but no lines of black or yellow off of either like with the salt solution.Observations for the salt solution: The iron nail gave off constant â€Å"streaks† of a blue/green color. The steel screw had constant â€Å"streaks† of yellow as well as many, many tiny bubbles the entire time. The nail also got much more dark after the salt solution. Part 2: Observations for the melting of sugar: Almost immediately the sugar began to melt. At first the sugar just turned from a pure, solid white to a white sugar that almost looked like more of a liquid. Then the sugar began to â€Å"pop† into tiny bubbles and quickly got faster.The tiny bubbles would then â€Å"grow† into larger brown bubbles. Observations for the salt solution: The salt solution created quiet popping noises after several seconds of being held above the candle. The salt t ook much longer to melt than the sugar. The salt also did not have near as large of a reaction as the sugar. The salt just turned darker, where as the sugar made huge bubbles. Questions 1. Why is it important to use distilled water instead of tap water used in Part 1? Distilled water is formed from condensed steam, which therefore makes it free from mineral and organic salts.Regular water is physically purified and chemically treated to kill germs, but contains many salts in it. Distilled water is free of salts, but regular tap water contains many salts. Therefore, if we are trying to see what happens for sugar, it would not be purely sugar if we used tap water because tap water contains salts. If we used tap water we would be mixing salt and sugar so we would not get accurate results. 2. In Part 1, why did you not observe a stream of bubbles coming off the stainless steel screw in the sugar solution?Since sugar is composed of covalent bonds and therefore as we saw in part 2, takes much less time to melt, I think we didn’t observe bubbles because there was not as much as a reaction since it â€Å"melted† so much faster. Also, sugar does not change its composition when added to water, but salt does. Therefore, perhaps the sugar does not cause the screw to bubble much. 3. Did any bubbles form off the screw in the sugar solution at all? Why might this happen despite your answer to Question 2? I did see occasional bubbles, which could be due to the slight chemical reaction of the two chemicals.However, it was obviously not as strong as with the salt since the salt changed its composition when added to water and so did the steel when exposed to the mixture. The transfer of energy might have been so great for the sugar that the sugar only reacted really briefly since it has a much lower melting point. However, the salt has a much higher melting point so perhaps the reaction was so much greater since the transfer of energy was so great, as needed with s alt, that there was more to react with for the salt than the sugar. 4.In Part 1, why did you observe a stream of bubbles coming off the steel screw in the salt solution? The salt solution created much more of a reaction and needs a much higher transfer of energy in order to react. The high transfer of energy created constant bubbles, where as with the sugar it did not. Perhaps the transfer of energy was so much for the salt solution that there were only really brief reactions. However, with the salt solution it needs so much energy in order to change so when all the energy is created in the salt solution, there is a much larger reaction. 5. Explain any changes that took place on the nail.The part of the nail that was exposed to the water changed in each solution. When it was in the sugar solution, the color changed very, very slightly. However, when the nail was placed in the salt solution, the part that was exposed changed a lot. The part that was in the salt solution became much d arker than the part that was not in the salt solution. 6. In Part 2, which of the substances had the lower melting point? Was this what you expected? Explain your results. The sugar had the lower melting point by a lot. The sugar immediately began to melt, but the salt took a lot longer to melt.The sugar began to melt so quickly since it was only held together by covalent bonds. The salt took a lot longer and had less of a reaction since it was held together by ionic bonds, which are much stronger. As explained in the pre-lab questions, this is exactly what I expected. The sugar melt with a much larger reaction as well (as can be seen in the photo below). The salt only popped and the individual crystals turned darker, where as the sugar actually melted and bursted into large bubbles. I think this is because it had such a low melting point that it created a large and immediate reaction.