Crystal making lab

Topics: Solution, Chemistry, Solubility Pages: 5 (624 words) Published: May 28, 2014
Crystal making lab
Purpose: To better understand saturated solutions, solubility . Analysis:
2. Why was it necessary to heat the water? Be specific.
Heating the water allows it to hold much more borax in solution than it could at room temperature. So after the water cooled, the ability of the solution to hold the solute inside decreases,this causes the excess borax in the solution to precipitate in crystal form on the string.When the water at a high temperature, water molecules have more kinetic energy, cause it has bigger space in solvent, more room for the solute. 3. Was this a saturated or unsaturated solution? Explain how you know ? This is a saturated solution, because borax is totally dissolved in the high temperature water at it maximum concentration, so when the temperature cool down, there has the crystal of borax inside the plastic yogurt container, this means at that temperature, the solution does not have enough space for the solute which is borax, so excess borax comes out form the solution then become to crystal.

4.What happened as the solution cooled overnight? Crystals are structures that are formed from a regular repeated pattern of connected atoms, ions or molecules. Explain and draw what is happening at the surface of the crystal as it grew on the pipe cleaner. There will be white crystal appears in the solution as the solution cooled overnight. Also borax becomes more transparent, because the temperature is cooled down, the solution molecules lost kinetic energy, and the attractive force between solvent molecules increases. 5. What does this lab have to do with solubility ?

Higher temperature will cause higher solubility, when the mass of borax add in the solvent is more than its solubility value at a changeless temperature, the solution will be saturated, and it could not dissolve borax in the solution anymore, except the pressure of the solution changes. This lab is at a constant pressure and it just have the temperature be changed, but it still influences borax solution to change the solubility of it, and makes borax crystallize.

6. What would happen if you added more water to your beaker after the crystal formed? Be specific. The crystal of borax will dissolve in the water again. More water means more solvent, so it changes the condition of this lab. Because c= n/ v, add more water causes the “V” value increase, so the solubility increases. This will cause two reactions which the solute molecules will break their bonds again and it will have intermolecular forces between the solute molecules. And the other reaction which is the solute molecules and solvent molecules combined to get the new bonds. The positive poles of the water molecules and the negative poles of the crystal will have attractive to cause the crystal dissolved.

Extension Question:
The original state of heat pack might be restored by boiling the heat pack and slowly letting it cool again. This gives the supersaturated solution which the pack had in the beginning.The pack is filled with a supersaturated solution of sodium acetate. A saturated solution is a solution in which the maximum possible amount of chemical at a given temperature is dissolved.These supersaturated solutions are not very stable, because the chemical actually does not want to exist as molecules at this lower temperature, but it prefers to be bound with other molecules in a crystal. The supersaturated solution is disturbed its the things happens in the pack. Doing this the solution not only warms up to the actual freezing temperature of the chemical, it releases energy in form of heat because you are forming bonds between atoms to get a crystal.

http://www.docin.com/p-438396823.html
Title: Hot & Cold Packs
1 Website title: DouDingWang
2 Accessed on: 2014-05-06
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